ALS - A+ Certification, Third Edition eBook

ALS - A+ Certification, Third Edition eBook
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Copyright © 2001 by Microsoft Corporation
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PUBLISHED BY
Microsoft Press
A Division of Microsoft Corporation
One Microsoft Way
Redmond, Washington 98052-6399
Copyright © 2001 by Microsoft Corporation
All rights reserved. No part of the contents of this book may be reproduced or
transmitted in any form or by any means without the written permission of the
publisher.
Library of Congress Cataloging-in-Publication Data
A+ Certification Training Kit / Microsoft Corporation.--3rd Ed.
p. cm.
ISBN 0-7356-1265-X
1. Electronic data processing personnel--Certification. 2. Computer
technicians--Certification--Study guides. I. Microsoft Corporation.
QA76.3 .A1755 2001
004.16--dc21
00-069440
Printed and bound in the United States of America.
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QWT
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About This Book
Welcome to the A+ Certification Training Kit. This technology-based training kit
is intended to provide the user with the skills necessary for A+ Certification. It
is a study of the computer—its hardware and software—from its earliest
beginnings, through the advent of mainframe and personal computers, up to
present-day Pentium processor-driven machines.
The computer industry has evolved and grown phenomenally since its
commercial inception in the 1960s. This industry is so vast and complex that
no one can claim to understand all its aspects. However, to participate in this
ever-changing and growing industry, the computer technician must be able to
demonstrate a level of proficiency with computers and technology. Certification
is a first step in establishing your presence as a computer professional. It
provides you with the opportunity to gain the skills you need, it helps you
establish your knowledge base, and it gives you the confidence to get started.
NOTE
For more information on becoming A+ Certified, refer to the
section titled "The A+ Certification Program," later in this
introduction.
Each chapter in this book is divided into lessons. Each lesson ends with a brief
summary, and each chapter concludes with a chapter summary and a set of
review questions to test your knowledge of the chapter material.
The "Getting Started" section of this introduction provides important
instructions that describe the hardware and software recommendations
presented in this course. Read through the section thoroughly before you start
the lessons.
Intended Audience
This book was developed for the entry-level computer technician, as well as
the experienced technician who is seeking certification. For the entry-level
student, it starts by explaining the basics and moves on to more complex
topics. It introduces the simple concepts that underlie today's computers. Once
this foundation is established, it brings you up to date with the latest
technology covered by the A+ Exam. For the more experienced user, it
provides a fresh review and focus on what is required to meet the objectives of
the A+ Exam.
Prerequisites
There are no formal prerequisites such as coursework or a specific knowledge
base. This is an entry-level course, and everything you need to know is
provided in the text. It is assumed that you are comfortable with computers,
can use simple hand tools (like a screwdriver), and are familiar with the
Microsoft Windows user interface.
To better understand the concepts presented and to complete any exercises or
practices, it would be useful to have a computer with an Intel Pentium
processor and, at the very least, a Microsoft Windows 98-based computer.
Both the Windows 98 and Microsoft Windows 2000 operating systems are
covered in the A+ Certification Program and this book. Please check the
Microsoft Web site at www.microsoft.com for possible trial versions of the
latest operating system.
About the CD-ROM
The companion compact disc contains informational aids that can be used to
supplement this book. These include demonstration videos and an electronic
version of the book.
The electronic version of the book requires an HTML (Hypertext Markup
Language) browser. If Microsoft Internet Explorer is installed on your system,
click Install E-Book. If AutoRun is disabled on your machine, refer to the
README.TXT file on the CD. The demonstrations are stored as HTML files with
embedded Microsoft Windows Media Player files. If your machine has standard
multimedia support and an HTML browser, you can view these demonstrations
by double-clicking them.
For specific information about what is included on the companion CD and how
to access this information, see the README.TXT file on the CD.
Features of This Book
Each chapter opens with a "Before You Begin" section, which prepares you for
completing the chapter.
The body of each chapter provides detailed coverage of the subjects you will
need to study to prepare for the test. The "Review" sections at the end of each
chapter allow you to test what you have learned in the chapter lessons. They
are designed to familiarize you with the types of questions you might
encounter on the exam.
Chapter and Appendix Overview
This self-paced training course combines instruction, procedures, multimedia
presentations, and review questions to teach you what you need to know for
A+ Certification. It is designed to be completed from beginning to end, but you
can choose a customized track and complete only the sections that interest
you. (See the next section, "Finding the Best Starting Point for You.") If you
choose the customized track option, be sure to check the "Before You Begin"
section in each chapter. Any concepts or procedures that require preliminary
work from preceding chapters will steer you to the appropriate chapters.
This self-paced book is divided into the following chapters:
This "About This Book" section contains a self-paced training overview
and introduces the components of this training. Read this section
thoroughly to draw the greatest educational value from the self-paced
training and to plan which lessons you will complete.
Chapter 1, "Introduction to Computers," sets the background for the rest
of the lessons. It provides a historic view of computers from their humble
beginnings to today's high-speed marvels. This section also explores the
role of today's computer technician.
Chapter 2, "Understanding Electronic Communication," discusses how
computers communicate. It explains the differences between the
language we use and the language of machines.
Chapter 3, "An Overview of the Personal Computer," defines the basic
elements of a computer's hardware and how they interact.
Chapter 4, "The Central Processing Unit," explains the development of the
microprocessor, focusing on what differentiates each type of processor
and how to identify each.
Chapter 5, "Power Supplies," covers power supplies, including how they
work and how to troubleshoot problems.
Chapter 6, "Motherboard and ROM BIOS," discusses the design and
function of primary foundation components: the motherboard and the
BIOS (basic input/output system).
Chapter 7, "Memory," covers the various types of memory found in a
computer, what memory is used for, and how to upgrade or replace it.
Chapter 8, "Expansion Buses, Cables, and Connectors," covers the
computer's I/O (input/output) components and expansion buses that
allow the PC to adapt and support new technology.
Chapter 9, "Basic Disk Drives," discusses floppy disk drives and hard disk
drives. It explores mass-storage devices, how they work, and their
limitations.
Chapter 10, "Advanced Disk Drive Technology," covers CD-ROM, digital
video disc (DVD), and SCSI (Small Computer System Interface) drives
and related technologies.
Chapter 11, "The Display System," covers monitors, flat screen panels,
display adapters, how they work, and how to troubleshoot them.
Chapter 12, "Printers," covers the different types of printers, how they
interact with the PC, and how to install and care for them.
Chapter 13, "Portable Computers," explores the features of portable
(laptop and notebook) computers.
Chapter 14, "Connectivity and Networking," discusses the basics of how a
computer network functions and technology that links a PC to the
network.
Chapter 15, "Telecommunications and the Internet," covers the
installation and use of modems and other telecommunications devices, as
well as the growing importance of the Internet to both technicians and
their clients.
Chapter 16, "Operating System Fundamentals," is an introduction to
operating systems and applications software. It focuses on the early
operating system MS-DOS, and how to use the DOS-mode command
prompt and programs that are still critical to performing many upgrade
and maintenance functions.
Chapter 17, "Introducing and Installing Microsoft Windows," discusses the
development of this now dominant operating system from Microsoft. It
presents the differences between the different versions and gives you a
foundation for the advanced skills presented in the following chapters.
Both Windows 9x and Windows 2000 installations are covered.
Chapter 18, "Running Microsoft Windows," covers the various tools
provided by the Windows 9x and Windows 2000 Professional operating
systems that a computer technician uses to manage and maintain both
the operating system and the hardware components of the computer.
Chapter 19, "Maintaining the Modern Computer," focuses on the tools and
techniques used to keep a computer operating properly, the use of system
software, and how to safeguard critical system files and user data.
Chapter 20, "Upgrading a Computer," covers the basic tools and
techniques used to perform common upgrades to a computer, including
upgrading memory, expansion card operations, and computer disassembly
and reassembly.
Chapter 21, "Troubleshooting Techniques and Client Relations," covers
the techniques and procedures used to resolve problems related to both
hardware and software. It also discusses how to recover from a complete
hard drive failure and corruption of core system files and how to deal with
clients.
Chapter 22, "The Basics of Electrical Energy," covers electricity and how it
relates to the computer. A computer technician does not need to be an
electrical engineer, but does need to be able to perform basic tests and to
work safely. This chapter provides the reader with background in these
issues.
Appendix A, "Questions and Answers," lists all the review questions from
each chapter of the book, including the page number where the question
appears, and provides suggested answers.
Appendix B, "Table of Acronyms," lists a number of acronyms relevant to
the A+ Certification Exam.
The Glossary provides concise definitions of terms used throughout this
book that are relevant to the A+ Certification Exam.
Finding the Best Starting Point for You
Because this book is self-paced, you can skip some lessons and visit them
later. Note, however, that some sections require an understanding of the
concepts presented in previous sections (prerequisites are noted at the
beginning of each chapter).
If…
Follow This Learning Path
You are preparing
to take the A+
Read the "Getting Started" section. Then work
Certification Exam
through Chapters 1 through 22 in order.
and have no
experience
You are preparing
to take the A+
Certification Exam
and are
experienced with
computer repair
Read the "Getting Started" section. Be sure to focus
on the exam objectives as presented in the "The A+
Certification Program" section of this introduction.
Then work through the remaining chapters in any
order you wish. Be sure, however, to cover all the
chapters.
You'd like to
review
information about
specific topics for
the exam
Use the "Where to Find Specific Skill Areas in This
Book" section that immediately follows this table.
Where to Find Specific Skill Areas in This Book
The following tables provide a list of the skill areas measured on the A+
Certification Exam. The tables list the skill and where in this book you will find
the lessons related to that skill.
A+ Core Hardware Examination
The objectives for the core exam focus on computer hardware. Information
relevant to the core exam objectives can be found in every chapter in this
training kit, except in those that specifically cover operating system material.
Skill Area Measured
Location in Book
Any chapter containing information
Installation, Configuration, and specific to devices (printers, monitors,
Upgrading
drives, and so on). Focus on Chapters 712 and 14, 15, and 20.
Diagnosing and
Troubleshooting
Chapter 21 and any chapter containing
information specific to devices (printers,
monitors, drives, and so on). Focus on
Chapters 8-13.
Safety and Preventive
Maintenance
Focus on Chapters 18 and 19. Other
safety and preventive maintenance tips
are found in sec- tions that cover a
specific device.
Motherboard/Processor/Memory Chapters 4, 6, and 7.
Printers
Chapter 12.
Portable Systems
Chapter 13.
Basic Networking
Chapter 14.
Customer Satisfaction
Chapter 21.
A+ Operating System Technologies Exam
The majority of information for this exam is found in Chapters 16 through 21.
Specific information regarding a device will be found in the chapter that covers
that device.
Skill Area Measured
Location in Book
Function, Structure, Operation, and File
Management
Chapters 16, 17, and 18.
Memory Management
Chapters 16 and 17. Also see
Chapter 7.
Installation, Configuration, and
Upgrading
Chapters 16, 17, and 18.
Troubleshooting
Chapter 21.
Networks
Chapters 14, 15, 16, and 17.
Getting Started
This self-paced training course contains hands-on procedures to help you learn
about computer hardware and software. Although it is not a requirement to
have a computer and software to complete the course, you will need one
available for practice. It is recommended that you not use a computer that
contains any important data that needs to be saved. Some of the concepts in
this book require complete reformatting of the hard drive or major
modifications of the operating system, during which all data will be lost.
Hardware Requirements
This course builds knowledge that begins with early technology. Therefore,
almost any computer will provide some level of skill building. In fact, a new
computer with a Pentium III processor and full Plug and Play capability will be
something of a detriment because it is overly capable for our purposes and
does not require the interaction necessary for building these basic skills.
However, to get the most out of this course, your computer should have the
following minimum configuration (all hardware should be on the Microsoft
Windows 98 or Windows 2000 Hardware Compatibility List):
Pentium II processor and motherboard
32 MB of RAM (64 MB or more recommended)
2-GB hard disk drive
3.5-inch floppy disk drive
CD-ROM drive (20x minimum recommended)
A mouse or other pointing device
Display system capable of 800 x 600 resolution or better (1024 x 768
recommended for best viewing of demonstration videos)
A printer
A modem with Internet connection
Software Requirements
The following software is required to complete the procedures in this course:
Windows 98 (minimum)
Microsoft Windows 2000 (recommended)
Access to earlier operating systems (Microsoft Windows 95 and MS-DOS)
is a plus
To view the electronic version of the book, you will need Microsoft Internet
Explorer 4.01 or later. A version of Microsoft Internet Explorer 5.5 is supplied
on the companion CD. For more information, see the README.TXT file on the
companion CD. To view the demonstration videos on the companion CD, you
will need a machine with standard multimedia support and an HTML browser. A
version of Microsoft Windows Media Player 7 is supplied on the companion CD.
About the Electronic Book
The companion CD also includes an electronic version of the book that you can
use to search and view on-screen as you work through the exercises. See the
README.TXT file on the companion CD for instructions on how to install and
use the electronic version of this book.
The A+ Certification Program
A+ Certification is a testing program sponsored by the Computing Technology
Industry Association (CompTIA) that certifies the competency of service
technicians in the computer industry. Many computer hardware and software
manufacturers, vendors, distributors, resellers, and publications back the
program.
Earning A+ Certification means that you possess the knowledge, skills, and
customer-relations expertise that are essential for a successful computer
service technician. The exams cover a broad range of hardware and software
technologies but are not related to any vendor-specific products, including
Microsoft Windows.
Benefits of Certification
For most individuals entering the computer industry, A+ Certification is only
the first step. If your goal is to enter the profession of computer service and
repair, this might be all the certification you need. However, if you are
interested in becoming a Microsoft Certified Systems Engineer (MCSE), this
course provides just the foundation you need to get on your way with
confidence.
As an A+ Certified Technician, you will receive many benefits, including:
Recognized proof of professional achievement. The A+ credential
asserts that the holder has reached a level of competence commonly
accepted and valued by the industry.
Enhanced job opportunities. Many employers give hiring preference to
applicants with A+ Certification. Some employers require A+ as a
condition of employment.
Opportunity for advancement. The A+ credential can be a plus when
an employer awards job promotions.
Training requirement. A+ Certification is being adopted as a
prerequisite to enrollment in certain vendors' training courses. Vendors
find they can cut their training programs by as much as 50 percent when
they require that all attendees are A+ Certified.
Customer confidence. As the general public learns about A+
Certification, customers will request that only certified technicians be
assigned to their accounts.
Companies benefit from improved productivity. Certified employees
perform work faster and more accurately. Statistics show that certified
employees can work up to 75 percent faster than noncertified employees.
Customer satisfaction. When employees have credentials that prove
their competency, customer expectations are more likely to be met. More
business can be generated for the employer through repeat sales to
satisfied customers.
The A+ Exam Modules and Domains
To become certified, you must pass two test modules: the Hardware Core and
the Operating System Technologies Core. For the most current rules
concerning taking the test, locations, fees, how the tests are administered, and
the requirements for passing, check the CompTIA Web site at
www.comptia.com.
This text prepares you to master the A+ Exams. By completing all course
work, you will be able to complete the A+ Certification Exams with the
confidence you need to ensure success. More important, you will be able to
conduct your business with the knowledge that you are among the best and
that you really "know your stuff."
Hardware Core Exam
This examination measures essential competencies for a microcomputer
hardware service technician with six months of on-the-job experience. It is
broken down into six sections (called domains). The following table lists the
domains and the extent to which they are represented.
Percent of
Examination
Domain
1.0—Installation, Configuration, and
Upgrading
30
2.0—Diagnosing and Troubleshooting
30
3.0—Preventive Maintenance
5
4.0—Motherboard/Processors/Memory
15
5.0—Printers
10
6.0—Basic Networking
10
1.0 Installation, Configuration, and Upgrading
This domain tests the knowledge and skills needed to identify, install,
configure, and upgrade microcomputer modules and peripherals, following
established basic procedures for system assembly and the assembly of field
replaceable modules. You will be expected to know how to
Identify basic terms, concepts, and functions of system modules, including
how each module should work during normal operation and during the
boot process.
Identify basic procedures for adding and removing field-replaceable
modules for both desktop and portable systems.
Identify common peripheral ports, associated cabling, and their
connectors.
Identify proper procedures for installing and configuring IDE/EIDE
devices.
Identify proper procedures for installing and configuring SCSI devices.
Identify proper procedures for installing and configuring peripheral
devices.
Identify hardware methods of upgrading system performance, procedures
for replacing basic subsystem components, unique components, and learn
when to use them.
Identify available IRQs (interrupt requests), DMA (direct memory access),
and I/O addresses and procedures for configuring them for device
installation.
2.0 Diagnosing and Troubleshooting
This domain tests the candidate's knowledge and skills in diagnosing and
troubleshooting common problems and system malfunctions, and requires
knowledge of the symptoms relating to common problems. You will be
expected to know how to
Identify common symptoms and problems associated with each module
and how to troubleshoot and isolate the problems.
Identify basic troubleshooting procedures and good practices for eliciting
problem symptoms from customers.
3.0 Preventive Maintenance
This domain requires the knowledge of safety and preventive maintenance.
With regard to safety, it includes potential hazards to personnel and
equipment when working with lasers, high-voltage equipment, electrostatic
discharge (ESD), and items that require special disposal procedures that
comply with environmental guidelines. With regard to preventive
maintenance, this includes knowledge of preventive maintenance products,
procedures, environmental hazards, and precautions when working on
microcomputer systems. You will be expected to know how to
Identify the purposes of various types of preventive maintenance
products and procedures and when to perform them.
Identify issues, procedures, and devices for protection within the
computing environment, including people, hardware, and the surrounding
workspace.
4.0 Motherboard/Processors/Memory
This domain requires knowledge of specific terminology, facts, ways and means
of dealing with classifications, and categories and principles of motherboards,
processors, and memory in microcomputer systems. You will be expected to
know how to
Distinguish between the popular CPU (central processing unit) chips in
terms of their basic characteristics.
Identify the categories of RAM (random access memory) terminology and
their locations and physical characteristics.
Identify the most popular types of motherboards, their components, and
their architecture (for example, bus structure and power supplies).
Identify the purpose of the CMOS (complementary metal-oxide
semiconductor) chip, what it contains, and how to change its basic
parameters.
5.0 Printers
This domain requires knowledge of basic types of printers, basic concepts, and
printer components; how they work, how they print onto a page; paper path,
care and service techniques, and common problems. You will be expected to
know how to
Identify the basic concepts, printer operations, and printer components.
Identify care and service techniques and common problems with primary
printer types.
6.0 Basic Networking
This domain tests skills and knowledge of basic network concepts and
terminology, ability to determine whether a computer is networked, knowledge
of procedures for swapping and configuring network interface cards, and
knowledge of the ramifications of repairs when a computer is on the network.
You will be expected to know how to
Identify basic networking concepts, including how a network works and
the ramifications of repairs on the network.
A+ Operating System Technologies Examination
For A+ Certification, the examinee must pass both this examination and the
A+ Core Hardware (formerly the A+ Core) Examination. This examination
measures essential operating system competencies for entry-level PC
hardware service technicians with six months of on-the-job experience. The
examinee must demonstrate basic knowledge of the command-line prompt,
Windows 9x, and Windows 2000 for installing, configuring, upgrading,
troubleshooting, and repairing microcomputer systems. This examination is
broken down into four domains.
Percent of
Examination
Domain
1.0—Operating System Fundamentals
30
2.0—Installation, Configuration, and
Upgrading
15
3.0—Diagnosing and Troubleshooting
40
4.0—Networks
15
1.0 Operating System Fundamentals
This domain tests required knowledge of underlying DOS (command prompt
functions), Windows 9x, and Windows 2000 operating systems in terms of
their function and structure, for managing files and directories, and reading
programs. It also includes navigating through the operating system from
command-line prompts and Windows procedures for accessing and retrieving
information. You will be expected to know how to
Identify the operating system's functions, structure, and major system
files to navigate the operating system and obtain needed technical
information.
Identify basic concepts and procedures for creating, viewing, and
managing files, directories, and disks. This includes procedures for
changing file attributes and the ramifications of those changes (for
example, security issues).
2.0 Installation, Configuration, and Upgrading
This domain requires knowledge of installing, configuring, and upgrading
Windows 9x and Windows 2000. This includes knowledge of system boot
sequences and minimum hardware requirements. You will be expected to know
how to
Identify the procedures for installing Windows 9x and Windows 2000 and
bringing the software to a basic operational level.
Identify steps to perform an operating system upgrade.
Identify the boot sequences and boot methods, including the steps to
create an emergency boot disk with utilities installed for Windows 9x,
Microsoft Windows NT, and Windows 2000.
Identify procedures for loading or adding and configuring device drivers,
applications, and the necessary software for certain devices.
3.0 Diagnosing and Troubleshooting
This domain requires the ability to apply knowledge to diagnose and
troubleshoot common problems relating to Windows 9x and Windows 2000.
This includes understanding normal operation and symptoms related to
common problems.
Recognize and interpret the meanings of common error codes and startup
messages from the boot sequence, and identify steps to correct the
problems.
Recognize common problems and determine how to resolve them.
4.0 Networks
This domain requires knowledge of the network capabilities of Windows and
how to connect to networks on the client side, including what the Internet is
about, its capabilities, basic concepts relating to Internet access, and generic
procedures for system setup. You will be expected to know how to
Identify the networking capabilities of Windows, including procedures for
connecting to the network.
Identify concepts and capabilities relating to the Internet and basic
procedures for setting up a system for Internet access.
Registering for the A+ Exams
The A+ Certification Exams are administered by Sylvan Prometric. They have
hundreds of authorized testing centers in all 50 states in the United States and
in more than 150 other countries worldwide. To register for the test call 1800-77-MICRO (1-800-776-4276).
When you call, please have the following information available:
Social Security number or Sylvan Prometric ID number (provided by
Sylvan Prometric)
Mailing address and telephone number
Employer or organization
Date on which you wish to take the test
Method of payment (credit card or check)
The test is available to anyone who wants to take it. Payment is made at the
time of registration, either by credit card or by requesting that an invoice be
sent to you or your employer. Vouchers and coupons are also redeemed at
that time.
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Chapter 1
Introduction to Computers
About This Chapter
We begin our introduction to computers with a brief history of how they
evolved. Although this course and the A+ exam focus on the modern electronic
computer, many principles used in early computational machines still apply to
their modern successors. With a summary of computer development and
discussion of the role of today's computer professional, this chapter lays the
foundation for the chapters that follow.
Before You Begin
There are no prerequisites for this chapter.
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Lesson 1: The Development of the Computer
In this lesson, we take a brief look at the development of the computer. By
understanding its origins, you'll gain an appreciation for both the complexity
and simplicity of today's computers.
After this lesson, you will be able to
Describe the major milestones in the development of the modern
computer
Estimated lesson time: 15 minutes
Many of us think only in terms of electronic computers, powered by electricity.
(If you can't plug it in, is it a computer?) But as the definition in Funk &
Wagnalls Standard College Dictionary makes clear, to "compute" is to
"ascertain (an amount or number) by calculation or reckoning." In fact, the
first computers were invented by the Chinese about 2500 years ago. They are
called abacuses and are still used throughout Asia today.
The Abacus
The abacus, shown in Figure 1.1, is a calculator; its first recorded use was
circa 500 B.C. The Chinese used it to add, subtract, multiply, and divide.
However, the abacus was not unique to the continent of Asia; archeological
excavations have revealed an Aztec abacus in use around 900 or 1000 A.D.
Figure 1.1 The first computer
The Analytical Engine (A Pre-Electronic Computer)
The first mechanical computer was the analytical engine, conceived and
partially constructed by Charles Babbage in London, England, between 1822
and 1871. It was designed to receive instructions from punched cards, make
calculations with the aid of a memory bank, and print out solutions to math
problems. Although Babbage lavished the equivalent of $6,000 of his own
money—and $17,000 of the British government's money—on this
extraordinarily advanced machine, the precise work needed to engineer its
thousands of moving parts was beyond the ability of the technology of the day
to produce in large volume. It is doubtful whether Babbage's brilliant concept
could have been realized using the available resources of his own century. If it
had been, however, it seems likely that the analytical engine could have
performed the same functions as many early electronic computers.
The First Electrically Driven Computer
The first computer designed expressly for data processing was patented on
January 8, 1889, by Dr. Herman Hollerith of New York. The prototype model of
this electrically operated tabulator was built for the U.S. Census Bureau to
compute results of the 1890 census.
Using punched cards containing information submitted by respondents to the
census questionnaire, the Hollerith machine made instant tabulations from
electrical impulses actuated by each hole. It then printed out the processed
data on tape. Dr. Hollerith left the Census Bureau in 1896 to establish the
Tabulating Machine Company to manufacture and sell his equipment. The
company eventually became IBM, and the 80-column punched card used by
the company, shown in Figure 1.2, is still known as the Hollerith card.
Figure 1.2 Typical 80-column punched card
The Digital Electronic Computer
The first modern digital computer, the ABC (Atanasoff–Berry Computer), was
built in a basement on the Iowa State University campus in Ames, Iowa,
between 1939 and 1942. The development team was led by John Atanasoff, a
professor of physics and mathematics, and Clifford Berry, a graduate student.
This machine utilized concepts still in use today: binary arithmetic, parallel
processing, regenerative memory, separate memory, and computer functions.
When completed, it weighed 750 pounds and could store 3000 bits (.4 KB) of
data.
The technology developed for the ABC machine was passed from Atanasoff to
John W. Mauchly, who, together with engineer John Presper Eckert, developed
the first large-scale digital computer, ENIAC (Electronic Numerical Integrator
and Computer). It was built at the University of Pennsylvania's Moore School
of Electrical Engineering. Begun as a classified military project, ENIAC was
designed to prepare firing and bombing tables for the U.S. Army and Navy.
When finally assembled in 1945, ENIAC consisted of 30 separate units, plus a
power supply and forced-air cooling. It weighed 30 tons, and used 19,000
vacuum tubes, 1500 relays, and hundreds of thousands of resistors,
capacitors, and inductors. It required 200 kilowatts of electrical power to
operate.
Although programming ENIAC was a mammoth task requiring manual switches
and cable connections, it became the workhorse for the solution of scientific
problems from 1949 to 1952. ENIAC is considered the prototype for most of
today's computers.
Another computer history milestone is the Colossus I, an early digital
computer built at a secret British government research establishment at
Bletchley Park, Buckinghamshire, England, under the direction of Professor
Max Newman. Colossus I was designed for a single purpose: cryptanalysis, or
code breaking. Using punched paper tape input, it scanned and analyzed 5000
characters per second. Colossus became operational in December 1943 and
proved to be an important technological aid to the Allied victory in World War
II. It enabled the British to break the otherwise impenetrable German
"Enigma" codes.
The 1960s and 1970s marked the golden era of the mainframe computer.
Using the technology pioneered with ABC, ENIAC, and Colossus, large
computers that served many users (with accompanying large-scale support)
came to dominate the industry.
As these highlights show, the concept of the computer has indeed been with us
for quite a while. The following table provides an overview of the evolution of
modern computers—it is a timeline of important events.
NOTE
Don't worry if you are not familiar with some terms in this
timeline; they are explained in the chapters that follow, as well as
in the Glossary.
Year
Events
1971
The 4004—the first 4-bit microprocessor—is introduced by Intel. It
boasts 2000 transistors with a clock speed of up to 1 megahertz
(MHz).
1972
The first 8-bit microprocessor—the 8008—is released.
1974
The 8080 microprocessor is developed. This improved version of
the 8008 becomes the standard from which future processors will
be designed.
1975
Digital Research introduces CP/M—an operating system for the
8080. The combination of software and hardware becomes the
basis for the standard computer.
1976
Zilog introduces the Z80—a low-cost microprocessor (equivalent
to the 8080).
The Apple I comes into existence, although it is not yet in
widespread use.
1977
The Apple II and the Commodore PET computers, both of which
use a 6502 processor, are introduced. These two products become
the basis for the home computer. Apple's popularity begins to
grow.
1978
Intel introduces a 16-bit processor, the 8086, and a companion
math coprocessor, the 8087.
Intel also introduces the 8088. It is similar to the 8086, but it
transmits 8 bits at a time.
1980
Motorola introduces the 68000—a 16-bit processor important to
the development of Apple and Atari computers. Motorola's 68000
becomes the processor of choice for Apple.
1981
The IBM personal computer (PC) is born; it contains a 4.7-MHz
8088 processor and 64 kilobytes (KB) of RAM (random access
memory), and is equipped with a version of MS-DOS 1.0 (three
files and some utilities).
Available mass-storage devices include a 5.25-inch floppy drive
and a cassette tape drive.
1982
Intel completes development of the 80286—a 16-bit processor
with 150,000 transistors.
MS-DOS 1.1 now supports double-sided floppy disks that hold 360
KB of data.
1983
IBM introduces the XT computer with a 10-MB hard disk drive.
MS-DOS 2.0 arrives; it features a tree-like structure and native
support for hard disk drive operations.
1984
The first computer with an 80286 chip—the IBM AT—enters the
market.
It is a 6-MHz machine with a 20-MB hard disk drive and a highdensity, 1.2-MB 5.25-inch floppy disk drive.
Apple introduces the Macintosh computer, marking the first
widespread use of the graphical user interface and mouse.
1985
MS-DOS 3.2, which supports networks, is released.
1986
The first Intel 80386-based computer is introduced by Compaq; it
features a 32-bit processor with expanded multitasking capability
(even though no PC operating system yet fully supports the
feature).
1987
MS-DOS 3.3 arrives, allowing use of 1.44-MB 3.5-inch floppy disk
drives and hard disk drives larger than 32 MB.
1988
IBM introduces the PS/2 computer series. A complete departure
from previous machines, its proprietary design does not support
the hardware and software available on IBM PCs or clones.
Microsoft (with the help of IBM) develops OS/2 (Operating System
2), which allows 32-bit operations, genuine multitasking, and full
MS-DOS compatibility.
Microsoft releases MS-DOS 4.0.
1989
Intel introduces the 80486 processor; it contains an on-board
math coprocessor and an internal cache controller (offering 2.5
times the performance of a 386 processor with a supporting
coprocessor).
1991
MS-DOS 5.0 offers a significantly improved DOS shell.
1992
The Intel i586 processor, the first Pentium, is introduced, offering
2.5 times the performance of a 486.
Microsoft introduces Windows 3.1, vastly expanding the use of a
graphical user interface in the mass market. IBM expands OS/2.
1993
MS-DOS 6.0 arrives. The term "multimedia" (the inclusion of CDROM drives, sound cards, speakers, and so forth, as standard
equipment on new personal computers) comes into use.
1994
Intel delivers the first 100-MHz processor. Compaq Computer
Corporation becomes the largest producer of computers.
1995
Windows 95, code-named Chicago, is introduced by Microsoft. It
features 32-bit architecture.
The Internet, having expanded far beyond its beginnings as a
network serving government and university institutions, is now in
everyday use by the rapidly growing proportion of the population
with access to a modem.
Computer prices drop as performance increases. IBM purchases
Lotus (maker of the popular Lotus1-2-3 spreadsheet).
1995- Software manufacturers scramble to make their products
1996 compatible with Windows 95.
1997
Microprocessor speeds exceed the 200-MHz mark. Hard disk drive
and memory prices fall as basic system configuration sizes
continue to increase.
CD-ROM drives and Internet connections have become standard
equipment for computers.
1998
PC performance continues to soar and prices continue to fall.
Central processing unit (CPU) speeds exceed 450 MHz, and
motherboard bus speeds reach 100 MHz
Entry-level machines are priced near the $500 mark.
Universal serial bus (USB) is introduced.
Windows 98 becomes the standard operating system for most new
personal computers. Computer prices drop well under $1,000,
increasing computer sales to the home market.
1999
Processor speeds exceed 1 gigahertz (GHz). E-commerce grows
dramatically as the Internet expands.
Microsoft releases Windows 2000 and the basic PC becomes a
commodity item in discount stores. Broadband connections such
2000
as DSL and cable begin to take hold, making Internet access
easier and faster than over the telephone line.
Lesson Summary
The following points summarize the main elements of this lesson:
The concepts that form the basis of computer technology have a long
history that stretches back 2500 years.
Rudimentary, electrically powered computers were first developed in the
1950s and 1960s.
The "standard" PC has undergone several stages of evolution,
characterized by improvements to the processor, internal architecture,
and types of storage devices.
3 4
Lesson 2: The Role of a Computer Service
Professional
As computers have evolved, so has the role of the computer technician. This
lesson takes a look at the contemporary technician's role in maintaining and
servicing computers.
After this lesson, you will be able to
Define your role as a modern computer technician
Estimated lesson time: 5 minutes
Matching the rapid pace of change in the industry, the role of the computer
professional is constantly changing, too. Not too many years ago, the only
tools needed to repair a computer were a screwdriver, needle-nose pliers, the
documentation for the computer, a boot disk with a few utilities, and a good
MS-DOS reference manual. The screwdriver is still the standard repair tool,
but the technician is confronted with a wider array of case types, motherboard
designs, processor types, and operating systems—and a wider array of
customer needs. Today's computer professional needs to be a technician,
scholar, and diplomat rolled into one, as you can see by the table that follows.
Title
Skills
Technician
You are able to troubleshoot and repair hardware and
software efficiently and quickly.
Scholar
You have the wisdom and perseverance to seek answers to
what you don't know and build your base of knowledge.
Learning never stops.
Diplomat
You are able to instill in the user (your customer) the
confidence that you are in control and can fix things, even
when you are encountering problems for the first time. You
are able to resolve the problem, even if your customer's (lack
of) understanding of the computer might be part of that
problem.
Lesson Summary
The following points summarize the main elements of this lesson:
To be competent, the computer technician of today must master a variety
of skills.
Understanding how a computer functions and how the owner plans to use
it are just as important to a technician as familiarity with parts and
workbench tools.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
The Development of the Computer
The concepts that form the basis of computer technology have a long
history that stretches back 2500 years.
Modern computers have followed the growth and technology of the
electronics industry.
The Role of a Computer Service Professional
The role of the computer technician has paralleled the evolution of the
computer.
A computer technician must combine troubleshooting and repair skills
with on-the-job learning and customer support.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Give an example of an early electronic computer.
2. What are the three roles that today's computer service professional needs
to assume?
Answers
3 4
Chapter 2
Understanding Electronic Communication
About This Chapter
We normally think of communication as an act that involves people and
activities like talking, writing, and reading. In this book, though, we are
interested also with communication between computers and between people
and computers. Communicating is the act of giving, transmitting, or
exchanging information. In this chapter, we discuss how a computer processes
data and communicates (transmits information) with its user. Understanding
this process is fundamental to understanding how computers work.
Before You Begin
There are no prerequisites for this chapter.
3 4
Lesson 1: Computer Communication
In this lesson, we examine the fundamentals of electronic communication and
explore how computer communication differs from human communication.
After this lesson, you will be able to
Understand how a computer transmits and receives information
Explain the principles of computer language
Estimated lesson time: 20 minutes
Early Forms of Communication
Humans communicate primarily through words, both spoken and written. From
ancient times until about 150 years ago, messages were either verbal or
written in form. Getting a message to a distant recipient was often slow, and
sometimes the message (or the messenger) got lost in the process.
As time and technology progressed, people developed devices to help them
communicate faster over greater distances. Items such as lanterns, mirrors,
and flags were used to send messages quickly over an extended visual range.
All "out of earshot" communications have one thing in common: They require
some type of "code" to convert human language to a form of information that
can be packaged and sent to the remote location. It might be a set of letters in
an alphabet, a series of analog pulses over a telephone line, or a sequence of
binary numbers in a computer. On the receiving end, this code needs to be
converted back to language that people can understand.
Obstacles to effective communications include differences in languages and in
how the speaker and listener give meaning to words. Language between
people is made up of more than words. Gestures, emphasis, body language,
and social concepts have an impact on how we interpret interpersonal
communications. Most of these elements have no bearing on human–machine
interactions. There are other issues we must understand to be able deal and
interact with computers.
Dots and Dashes, Bits and Bytes
Telegraphs and early radio communication used codes for transmissions. The
most common, Morse code (named after its creator, Samuel F. B. Morse), is
based on assigning a series of pulses to represent each letter of the alphabet.
These pulses are sent over a wire in a series. The operator on the receiving
end converts the code back into letters and words. Morse code remained in
official use for messages at sea almost until the end of the twentieth century—
it was officially retired in late 1999.
Morse used a code in which any single transmitted value had two possible
states: a dot or a dash. By combining the dots and dashes into groups, an
operator was able to represent letters and, by stringing them together, words.
That form of on–off notation can also be used to provide two numbers, 0 and
1. The value 0 represents no signal, or off, and the value 1 represents a
signal, or on, state.
This type of number language is called binary notation because it uses only
two digits, usually 0 and 1. It was first used by the ancient Chinese, who used
the terms yin (empty) and yang (full) to build complex philosophical models of
how the universe works.
Our computers are complex switch boxes that have two states and use a
binary scheme. The value of a given switch's state—on or off—represents a
value that can be used as a code. Modern computer technology uses terms
other than yin and yang, but the same binary mathematics creates virtual
worlds inside our modern machines.
The Binary Language of Computers
The binary math terms that follow are fundamental to understanding PC
technology.
Bits
A bit is the smallest unit of information that is recognized by a computer: a
single on or off event.
Bytes
A byte is a group of 8 bits. A byte is required to represent one character of
information. Pressing one key on a keyboard is equivalent to sending 1 byte of
information to the computer's central processing unit (CPU). A byte is the
standard unit by which memory is measured in a computer—values are
expressed in terms of kilobytes (KB) or megabytes (MB). The table that follows
lists units of computer memory and their values.
Memory
Unit
Value
Bit
Smallest unit of information; shorthand term for binary digit
Nibble
4 bits (half of a byte)
Byte
8 bits (equal to one character)
Word
16 bits on most personal computers (longer words possible
on larger computers)
Kilobyte
(KB)
1024 bytes
Megabyte
(MB)
1,048,576 bytes (approximately 1 million bytes or 1024 KB)
Gigabyte
(GB)
1,073,741,824 bytes (approximately 1 billion bytes or 1024
MB)
The Binary System
The binary system of numbers uses the base of 2 (0 and 1). As described
earlier, a bit can exist in only two states, on or off. When bits are represented
visually:
0 equals off.
1 equals on.
The following is 1 byte of information in which all 8 bits are set to 0. In the
binary system, this sequence of eight 0s represents a single character—the
number 0.
0
0
0
0
0
0
0
0
The binary system is one of several numerical systems that can be used for
counting. It is similar to the decimal system, which we use to calculate
everyday numbers and values. The prefix dec in the term decimal system
comes from the Latin word for 10 and denotes a base of 10, which means the
decimal system is based on the 10 numbers 0 through 9. The binary system
has a base of 2, the numbers 0 and 1.
Counting in Binary Notation
There are some similarities in counting with binary notation and the decimal
system we all learned in grade school. In the decimal system, the rightmost
whole number (the number to the left of the decimal point) is the "digits"
column. Numbers written there have a value of 0 to 9. The number to the left
of the digits column (if present) is valued from 10 to 90—the "10s" column.
The factor of each additional row is 10 in the decimal system of notation. To
get the total value of a number, we add together all columns in both systems:
111 is the sum of 100 + 10 + 1.
NOTE
A factor is an item that is multiplied in a multiplication problem.
For example, 2 and 3 are factors in the problem 2 × 3.
Binary notation uses the same system of right-to-left columns of ascending
values, but each row has only two (0 or 1) instead of 10 (0–9) possible
values.Thus, in the binary system, the first row to the right can be only 0 or 1;
the next row to the left can be 2 or 3 (if a number exists in that position). The
columns that follow have values of 4, then 8, then 16, and so on, each column
doubling the possible value of the one to its right. The factor used in the
binary system is 2, and—just as in the decimal system—0 is a number counted
in that tally. Examples of bytes of information (eight rows) follow.
Byte—Example A
The value of this byte is 0 because all bits are off (0 = off).
0
128
0
64
0
32
0
16
0
8
0
4
0
2
0
1
8
#
bits
values
Byte—Example B
In this example, two of the bits are turned on (1 = on). The total value of this
byte is determined by adding the values associated with the bit positions that
are on. This byte represents the number 5 (4 + 1).
0
128
0
64
0
32
0
16
0
8
1
4
0
2
1
1
8
#
bits
values
Byte—Example C
In this example, two different bits are turned on to represent the number 9 (8
+ 1).
0
128
0
64
0
32
0
16
1
8
0
4
0
2
1
1
8
#
bits
values
The mathematically inclined will quickly realize that 255 is the largest value
that can be represented by a single byte. (Keep in mind that we start with 0
and go to 255, which corresponds to a possible 256 places on a number line.)
Because computers use binary numbers and humans use decimal numbers, A+
technicians must be able to perform simple conversions. The following table
shows decimal numbers and their binary equivalents (0_9). You will need to
know this information. The best way to prepare is to learn how to add in
binary numbers rather than merely memorizing the values.
Decimal Number
Binary Equivalent
0
0000
1
0001
2
0010
3
0011
4
0100
5
0101
6
0110
7
0111
8
1000
9
1001
Numbers are fine for calculating, but today's computers must handle text,
sound, streaming video, images, and animation as well. To handle all of that,
standard codes are used to translate between binary machine language and
the type of data being represented and presented to the human user. The
binary system is still used to transfer values, but those values have a
secondary meaning that is handled by the code. The first common, code-based
language was developed to handle text characters and serves as a good
example that lets us examine some other core concepts as well.
Parallel and Serial Devices
The telegraph and the individual wires in our PCs are serial devices. This
means that only one element of code can be sent at a time. Like a one-lane
tunnel, there is only room for one person to pass through at one time. All
electronic communications are—at some level—serial, because a single wire
can have only two states: on or off.
To speed things up, we can add more wires. This allows simultaneous
transmission of signals. Or, to continue our analogy, it's like adding another
set of tunnels next to the first one: We still have only one person per tunnel,
but we can get more people through because they are traveling in parallel.
That is the difference between parallel and serial data transmission. In PC
technology, we often string eight wires in a parallel set, allowing 8 bits to be
sent at once. Figure 2.1 illustrates serial and parallel communication.
Figure 2.1 Serial and parallel communication
ASCII Code
The standard code for handling text characters on most modern computers is
called ASCII (American Standard Code for Information Interchange). The basic
ASCII standard consists of 128 codes representing the English alphabet,
punctuation, and certain control characters. Most systems today recognize 256
codes: the original 128 and an additional 128 codes called the extended
character set.
Remember that a byte represents one character of information; 4 bytes are
needed to represent a string of four characters. The following 4 bytes
represent the text string 12AB (using ASCII code):
00110001
1
00110010
2
01000001
A
01000010
B
The following illustrates how the binary language spells the word binary:
B
01000010
I
01001001
N
01001110
A
01000001
R
01010010
Y
0101100
NOTE
It is very important to understand that in computer processing, the
"space" is a significant character. All items in a code must be set
out for the machine to process. Like any other character, the space
has a binary value that must be included in the data stream. In
computing, the absence or presence of a space is critical and
sometimes causes confusion or frustration among new users.
Uppercase and lowercase letters also have different values. Some
operating systems (for example, UNIX) distinguish between them
for commands, whereas others (for example, MS-DOS) translate
the uppercase and lowercase into the same word no matter how it
is cased.
The following table is a partial representation of the ASCII character set. Even
in present-day computing, laden with multimedia and sophisticated
programming, ASCII retains an honored and important position.
Symbol Binary 1 Byte Decimal Symbol Binary 1 Byte
Decimal
0
00110000
48
V
01010110
86
1
00110001
49
W
01010111
87
2
00110010
50
X
01011000
88
3
00110011
51
Y
01011001
89
4
00110100
52
Z
01011010
90
5
00110101
53
a
01100001
97
6
00110110
54
b
01100010
98
7
00110111
55
c
01100011
99
8
00111000
56
d
01100100
100
9
00111001
57
e
01100101
101
A
01000001
65
f
01100110
102
B
01000010
66
g
01100111
103
C
01000011
67
h
01101000
104
D
01000100
68
i
01101001
105
E
01000101
69
j
01101010
106
F
01000110
70
k
01101011
107
G
01000111
71
l
01101100
108
H
01001000
72
m
01101101
109
I
01001001
73
n
01101110
110
J
01001010
74
o
01101111
111
K
01001011
75
p
01110000
112
L
01001100
76
q
01110001
113
M
01001101
77
r
01110010
114
N
01001110
78
s
01110011
115
O
01001111
79
t
01110100
116
P
01010000
80
u
01110101
117
Q
01010001
81
v
01110110
118
R
01010010
82
w
01110111
119
S
01010011
83
x
01111000
120
T
01010100
84
y
01111001
121
U
01010101
85
z
01111010
122
NOTE
All letters have a separate ASCII value for uppercase and
lowercase. The capital letter "A" is 65, and the lowercase "a" is 97.
Keep in mind that computers are machines, and they do not really "perceive"
numbers as anything other than electrical charges setting a switch on or off.
Like binary numbers, electrical charges can exist in only two states—positive
or negative. Computers interpret the presence of a charge as 1 and the
absence of a charge as 0. This technology allows a computer to process
information.
Lesson Summary
The following points summarize the main elements of this lesson:
Computers communicate using binary language.
A bit is the smallest unit of information that is recognized by a computer.
ASCII is the standard code that handles text characters for computers.
3 4
Lesson 2: The Computer Bus
This lesson discusses the set of hardware lines, or conductors, by which data is
transferred internally in the components of a computer system.
After this lesson, you will be able to
Understand the concept of an electronic bus
Estimated lesson time: 5 minutes
For efficient use of system resources, most communications within a computer
need to occur at a much quicker rate than processing signals one at a time
would allow. Therefore, the computer moves information through a bus.
Several types of buses are used within a computer, and they are discussed
more fully in later chapters. For now, let's simply look at what a bus is and
how it works.
A bus is a group of electrical conductors—usually wires—running parallel to
one another that can carry a charge from one point to another. These
conductors can be copper traces on a circuit board or wires in a cable. Usually,
they are found in multiples of eight (8, 16, 32, 64, and so on). Early
computers used eight conductors for the main system bus, thereby allowing
the transmission of 8 bits, or 1 byte, of information at a time. Figure 2.2
illustrates an 8-bit and a 16-bit bus.
Figure 2.2 Computer bus
The physical configuration of a bus isn't as important as its function. A bus
provides a common path along which to transmit information in the form of
code. It allows any device to receive information from or send information to
any other device on the same bus. This is not unlike the telegraph system, in
which a single wire was strung from one end of the country to the other. Any
town that tapped into the wire could exchange information with any other
town also connected to the wire.
Another familiar example of a bus system is the electrical wiring in a home or
office. The 110-volt AC outlets are wired with three wires—hot, neutral, and
ground—that run in parallel from one outlet to another. Each time a device is
plugged in, it is connected to the bus, in parallel (see Figure 2.3).
Figure 2.3 Connecting to a bus
Remember, in a computer, a bus is a set of parallel wires or lines to which the
CPU, the memory, and all input/output devices are connected. Everything in a
computer is connected to a bus. The actual number of wires, or lines, in a bus
can vary from one computer to another or even from one part of a computer
to another. The bus contains one line for each bit needed to give the address
of a device or a location in memory. It also contains one line for each bit of
data being transmitted from device to device.
A manufacturer might also use additional lines for power or other
communication within the computer. When we speak of buses within a
computer (data bus, expansion bus, or address bus), we are speaking of a
specific number of wires dedicated to a specific purpose—connecting parts of
the computer to each other for the exchange of data between components.
Lesson Summary
The following points summarize the main elements of this lesson:
A bus is the physical means by which data is made to move inside a
computer.
A bus can take on many different shapes (wires, flat cables, circuit
traces), but it is basically a group of parallel wires.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Computer Communication
Computers communicate using binary language.
An A+ technician must be able to convert decimal numbers to binary and
binary numbers to decimal.
ASCII is the standard code that handles text characters for computers.
The Computer Bus
A computer uses a bus to move data from one device to another.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. What is the definition of a bus in a computer?
2. What is the purpose of the computer bus?
3. Define the term decimal.
4. Describe the difference between serial and parallel communication.
5. What is binary code language?
6. How does ASCII use binary code to represent numbers or characters?
7. Define a bit.
8. Define a byte.
9. Which decimal number does the following binary number represent:
00001001?
10. What do 1s and 0s represent in computer operation?
11. Computer buses are usually made of multiples of ___________ wires or
traces.
Answers
3 4
Chapter 3
An Overview of the Personal Computer
About This Chapter
In this chapter, we expand on the material in the preceding chapters with an
explanation of the Input/Process/Output (I/P/O) model and see how it can be
used to help us understand the functional design of the personal computer
(PC). We go on to define the hardware components that a computer
professional can expect to encounter every day—the computer parts that you
actually touch.
Before You Begin
If possible, while you work through this chapter, have a PC at hand with its
case open. Take a look at each piece of hardware and try to identify its
function as you go over this material.
3 4
Lesson 1: The Three Stages of Computing
In this lesson, we discuss the three stages of computing and how they relate to
the constituent parts that make up the modern PC.
After this lesson, you will be able to
Describe the three stages of computing
Estimated lesson time: 5 minutes
A modern computer looks like a complicated device. On one level this is true,
and it is the beneficiary of much development in electronics technology. It is
constructed of many hardware components connected with what seem to be
miles of interwoven wires. Despite this apparent complexity, however, a
computer, just like a calculator, handles information in three stages: input,
processing, and output (see Figure 3.1). Each piece of hardware can be
classified as working in one (and sometimes two) of these three stages. We
can also use these three stages to classify any aspect of a computer's
operation or the function of any of its components. During the troubleshooting
phase of a repair job, it is often useful to categorize a problem according to
which of the three stages it occurs in.
Figure 3.1 Three stages of computing
Input
Input is the first stage of computing, referring to any means that moves data
(information) from the outside world into the processor—or from one
component of the computer to another. Today's PC can support a wide variety
of input devices. Keyboards, mouse devices, voice recognition devices, sound
cards, modems, scanners, tape drives, CD/DVD drives, and digital cameras are
some of the most common.
Processing
Processing is the second stage of computing. This is the actual manipulation of
data by the computer. Processing on early computers involved the tedious task
of "number crunching" and then, later, storing large amounts of oftenredundant data. Today, computers process an ever-expanding list of activities,
including scientific and business tasks, as well as processing information for
education, entertainment, organization, and much more. Computer processing
technology also hides in many everyday appliances. Microprocessors run most
of our mechanical and electronic devices including cars, cameras, VCRs,
microwave ovens, telephones, and even supermarket checkout systems.
Output
Output is the third stage of computing. All the input and processing in the
world won't do us any good unless we can get the information back from the
computer in a comprehensible and usable form. Output devices today come in
many forms: monitors, printers, fax machines, modems, plotters, CD-Rs,
sound cards, and more.
Input, Processing, and Output
Whenever you sit down at a computer and run an application—whether it is a
game, spreadsheet, database, or word processor—you are an active part of the
input, processing, and output operation of that computer. The following table
provides some examples.
Application
Word
processor
Function
Input: Typing your words
Processing: Formatting the text (such as word wrap and
fonts)
Output: Storing the text and allowing you to retrieve or
print it
Input: Typing or providing numbers (such as sales figures)
Processing: Applying one or more formulas to the data
Spreadsheet
Output: Displaying the results of the calculation in numeric
or graphical form
Database
Input: Typing information into a data form
Processing: Indexing and storing the data records
Output: Producing reports showing selected data records
Game
Input: Moving your chess piece
Processing: Computer calculating how to respond to your
move
Output: Computer making a move
Keep in mind that this is a short list focusing on human interaction with the
machine. The PC often takes information for its own components and processes
that data for internal use, as when a drive is accessed or a display adapter
sends signals to the monitor.
Lesson Summary
The following points summarize the main elements of this lesson:
All computer hardware can be classified according to its primary function:
input, processing, or output.
Any time you sit down at a computer and run an application, you are
using the input, processing, and output stages of computing.
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Lesson 2: Components of a Computer
In this lesson, we take a look at the different components of a computer
system.
After this lesson, you will be able to
Define the primary components that make up a computer
Estimated lesson time: 10 minutes
As you might expect, the components of a computer reflect the function of the
machine—specifically, the three stages of computing, as outlined in Lesson 1.
Let's examine the components.
Input
The following table lists some examples of devices that are used to put
information into a computer.
Device
Description
Keyboard
The primary input
device for a computer,
allowing users to type
information just as
they once did on a
typewriter.
Mouse
Used with graphical
interface environments
to point to and select
objects on the
system's monitor. Can
be purchased in a
variety of sizes,
shapes, and
configurations.
Scanner
Converts printed or
photographic
information to digital
information that can
be used by the
computer. Works
similar to the scanning
process of a photocopy
machine.
Works like the
microphone on a tape
recorder. Allows input
Microphone of voice or music to be
converted to digital
information and saved
to a file.
CDROM/DVD
drive
Compact disc–read
only memory: stores
large amounts of data
on a CD that can be
read by a computer.
Processing
The central processing unit (CPU) is the heart and brain of the computer. This
one component, or "chip," is responsible for all primary number crunching and
data management. It is truly the centerpiece of any computer. It is so
important that whole generations of computer technology are based and
measured on each "new and improved" version of the CPU.
When we refer to the CPU, we are usually speaking of the processor. However,
the CPU requires several other components that support it with the
management of data to operate. These components, when working in
harmony, make up the primary elements of the PC we know today. The
following table lists these fundamental support components.
Component
Description
The large circuit
board found inside
the computer.
Without it, a
computer is just a
metal box. The
Motherboard
motherboard
contains all the
remaining items in
this table; for all
practical purposes, it
is the computer.
Chip set
A group of computer
chips or integrated
circuits (ICs) that,
when working
together, manage
and control the computer system. This
set includes the CPU
and other chips that
control the flow of
data throughout the
system.
A group of parallel
conductors (circuit
traces) found on the
motherboard and
Data bus
used by the CPU to
send and receive
data from all the
devices in the
computer.
A group of parallel
conductors (circuit
traces) found on the
motherboard and
used by the CPU to
Address bus "address" memory
locations.
Determines which
information is sent
to, or received from,
the data bus.
Expansion
slots
Clock
Specialized sockets
that allow additional
devices called
expansion cards or,
less commonly,
circuit boards, to be
attached to the
motherboard. Used
to expand or
customize a
computer, they are
extensions of the
computer's bus
system.
Establishes the
maximum speed at
which the processor
can execute
commands. Not to
be confused with the
clock that keeps the
date and time.
Battery
Protects unique
information about
the setup of the
computer against
loss when electrical
power fails or is
turned off. Also
maintains the
external date and
time (not to be
confused with the
CPU's clock).
Memory
Stores temporary
information (in the
form of data bits)
that the CPU and
software need to
keep running.
Output
The following table lists some common devices, known as peripherals, used
exclusively for output.
Device
Description
Printer
Generates a "hard copy" of
information. Includes dot
matrix, ink jet, and laser
varieties.
Monitor
The primary output device.
Visually displays text and
graphics.
Plotter
Similar to a printer, but uses
pens to draw an image. Most
often used with graphics or
drawing programs for very large
drawings.
Reproduce sound. Optional
high-quality speakers can be
Speakers added to provide improved
output from games and
multimedia software.
Input and Output
Some devices handle both input and output functions. These devices are called
input/output (I/O) devices, a term you will encounter quite often.
Device
Description
Floppy
disk
drive
Mechanism for reading and
writing to low-capacity,
removable, magnetic disks.
Used to store and easily
transport information.
Hard
disk
drive
High-capacity internal (and
sometimes external) magnetic
disks for storing data and
program files. Also called fixed
disks.
Modem
Converts computer data to
information that can be
transmitted over telephone
wires and cable lines. Allows
communication between
computers over long and short
distances.
An expansion card that allows
several computers to connect to
Network each other and share
card
information and programs. Also
called network interface card
(NIC).
Also called CD-R. You can copy
data to a CD with this device,
but you can only write to a
section of the disc once.
CD
Variations on this type of device
recorder include compact disc–rewritable
(CD-RW) drives. These drives
allow you to read, write, and
overwrite a special CD-ROMtype disc.
Tape
drive
Large-capacity, magnetic, data
storage devices. Ideal for
backup and retrieval of large
amounts of data. Works like a
tape recorder and saves
information in a linear format.
Other external storage devices include Iomega Zip drives, which allow users to
store 100 MB or 250 MB of data on a single Zip disk.
Lesson Summary
The following points summarize the main elements of this lesson:
All computer hardware can be classified by primary function (input,
processing, or output).
Some hardware devices combine multiple functions (input and output).
3 4
Lesson 3: Support Hardware
Lesson 2 covered the basic hardware that makes up a computer. There are,
however, additional components needed to support safe computer operation.
In this lesson, we look at several devices that protect and enhance the value
of a computer.
After this lesson, you will be able to
Identify additional support hardware for a computer
Understand the functions of some of the add-on hardware
Estimated lesson time: 5 minutes
In addition to the devices that support a computer's data-processing functions,
there are others that enhance its operation and performance. The following
table lists some of these devices.
Device
Power
supply
Description
Converts a local power
source (typically 110
volts AC in the United
States) to 3.3, 5, or
12 volts DC. Most
power supplies also
perform some basic
line conditioning and
surge-protection
functions.
Used to prevent large
power spikes (for
Surge
instance, lightning)
suppressor
from damaging a
computer.
Uninterruptible power
supply. Acts as both a
UPS
Case
surge suppresser (to
prevent high-power
spikes) and a power
leveler to provide the
computer with a
constant source of
power. Can even
provide power during
a power failure or
interruption (although
the duration depends
on the UPS and the
computer's power
consumption) so that
the user can safely
save data before
shutting down.
The box that houses
most of the system
must provide an
environment that
minimizes electrical
interference to other
electronic devices in
the area. It should
provide a proper heat
level for safe
operation and bays
and connections for
drives, circuit boards,
and I/O devices.
Don't let the term support hardware lead you to underestimate the importance
of these components. How important are roads to commerce, or water to a
city? Without a reliable power source, modern PCs would not exist. The
internal power supply keeps a clean current running to the system.
Lesson Summary
The following points summarize the main elements of this lesson:
Support equipment protects a computer or makes it easier to operate.
Support equipment, such as the power supply, is critical to the operation
of the computer.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
The Three Stages of Computing
Computing occurs in three stages: input, processing, and output.
All computer hardware can be classified in one or more of these stages.
Components of a Computer
An input device retrieves data from an outside source and brings it into
the computer for processing.
A processing device takes information and alters it in some useful
manner.
An output device takes the altered information and stores or displays it.
Support Hardware
Computers require additional components to protect operations and
ensure optimal performance.
Use of surge suppressors and UPSs can protect computers from damage
caused by power spikes and surges.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Describe the three stages of computing and the role of each.
2. What is the purpose of the central processing unit (CPU)?
3. Describe two devices that process information inside a computer.
4. What is a chip set?
5. Name and describe three input devices.
6. What type of device is a scanner?
7. Describe three output devices.
8. What is I/O?
9. Name three I/O devices.
Answers
3 4
Chapter 4
The Central Processing Unit
About This Chapter
This chapter presents an overview of the CPU (central processing unit), which
functions as the "brain" of the personal computer. Like the human brain, a
CPU is a complicated, highly integrated component performing many
simultaneous functions. Understanding the principles that underlie the
workings of the microprocessor is critical to understanding the computer and
its operation.
Before You Begin
You should be familiar with the terms and concepts introduced in Chapter 1,
"Introduction to Computers," and Chapter 2, "Understanding Electronic
Communication."
3 4
Lesson 1: Microprocessors
A microprocessor is an integrated circuit (IC) that contains a complete CPU on
a single chip. In this lesson, we examine the microprocessor from its inception
to the current state-of-the-art chip. It is important for a computer technician
to understand the development of the processor and what makes each version
different from its predecessors. This knowledge gives us an understanding of
the enhancements each new design offers over earlier ones and how the
system components can take advantage of the new features.
After this lesson, you will be able to
Describe how a microprocessor works
Define different types of processors and describe their advantages and
limitations
Estimated lesson time: 40 minutes
Fortunately, computer technicians aren't required to design microprocessors,
only to understand how they work. Microprocessors can be viewed as little
black boxes that provide answers or perform a variety of chores on command.
We also need to understand the external data bus because it is the means by
which the CPU accesses system resources.
The External Data Bus
In previous lessons, you learned that information is transmitted throughout a
computer using binary code traveling through a bus. The external data bus
(also known as the external bus or simply data bus) is the primary route for
data in a PC (personal computer). All data-handling components or optional
data devices are connected to it; therefore, any information (code) placed on
that bus is available to all devices connected to the computer.
As mentioned in Chapter 1, "Introduction to Computers," early computers used
eight conductors (an 8-bit data bus), which allowed for the transfer of 1 byte
of information at a time. As computers evolved, the width of the external data
bus increased to 16, 32, and the current width of 64 conductors. The wider bus
lets more data flow at the same time, just as adding more lanes to a highway
allows more cars to move through a point in a given amount of time.
Figure 4.1 shows a Pentium II CPU attached to its motherboard. The motherboard is the main circuit board, which contains the external data bus and
connection for expansion devices that are not part of the board's basic design.
Expansion slots act as "on ramps" to the external bus. Expansion cards, once
commonly known as daughter cards, are placed in slots on the motherboard.
Other forms of on ramps are the slots that hold memory or the sets of pins
used to attach drive cables. Connectors on the motherboard grant access to
the data bus for keyboards, mouse devices, and peripheral devices like
modems and printers through the use of COM and LPT ports.
Figure 4.1 Motherboard
To understand how a computer moves data between components, visualize
each device on the data bus (including the CPU) connected to the bus by
means of a collection of on-off switches. By assessing which conductors have
power and which ones do not, the device can read the data as it is sent by
another device. The on-off state of a line gives the value of 0 (off) or 1 (on).
The wires spell out a code of binary numbers that the computer interprets and
then routes to another system component or to the user by means of an
output device such as a monitor or printer. Communication occurs when
voltage is properly applied to or read from any of the conductors by the
system. Figure 4.2 illustrates a data bus connected to a CPU and a device.
Figure 4.2 External data bus
Coded messages can be sent into or out of any device connected to the
external data bus. Think of the data bus as a large highway with parallel lanes.
Extending that analogy, bits are like cars traveling side by side—each carries
part of a coded message. Microprocessors are used to turn the coded messages
into data that performs a meaningful task for the computer's user.
NOTE
All hardware that uses data is connected in some way to the data
bus or to another device that is connected to the data bus.
The CPU
The CPU is the part of a computer in which arithmetic and logical operations
are performed and instructions are decoded and executed. The CPU controls
the operation of the computer. Early PCs used several chips to handle the task.
Some functions are still handled by support chips, which are often referred to
collectively as a chip set. Figure 4.3 shows a close-up of the working portion of
a CPU.
Figure 4.3 Close up of a CPU
Although it is not necessary to know exactly what goes on inside the
processor, learning a few terms that you will encounter as a computer
professional will help you in the discussion that follows.
Transistors
Transistors, the main components of microprocessors, are small, electronic
switches. The on–off positions of the transistors form the binary codes
discussed earlier in this lesson. Although transistors might seem simple, their
development required many years of painstaking research. Before transistors
were available, computers relied on slow, inefficient vacuum tubes and
mechanical switches to process information. The first large-scale computers
took up a huge amount of space, and technicians actually went inside them to
"program" by turning on and off specific tubes!
Many materials, including most metals, allow electrical current to flow through
them; these are known as electrical conductors. Materials that don't pass
electrical current are called insulators. Pure silicon, which is used to make
most transistors, is a semiconductor; its degree of conductivity can be
adjusted, or modulated, by adding impurities during production.
Transistor switches have three terminals: the source, the gate, and the drain.
When positive voltage is applied to the gate, electrons are attracted, forming
an electron channel between the source and the drain. Positive voltage applied
to the drain pulls electrons from the source to the drain, turning the transistor
on. Removing the voltage turns it off by breaking the pathway.
In the late 1950s, a major development in transistor technology took place. A
team of engineers put two transistors on a silicon wafer, creating the world's
first IC and paving the way for the development of compact computers.
Integrated Circuits
An IC is an electronic device consisting of a number of miniature transistors
and other circuit elements (resistors and capacitors, for instance). An IC
functions just as a large collection of these parts would, but it is a fraction of
the size and uses a fraction of the power. ICs make today's microelectronics
possible. The original transistors were small plastic boxes about the size of a
peanut that could handle only one function. The word integrated denotes that
IC devices combine many circuits—and some of their functions—into one
package. A prime example of this technology is the microprocessor.
Microprocessors
On November 15, 1971, Intel shipped the commercial microprocessor Model
4004. It ran a product called the Busicom calculator. The 108-KHz 4004 had
2300 transistors and a 4-bit data bus and could address 640 bytes of RAM.
Computer engineers quickly took advantage of the potential this new type of
chip offered, leading the way to the first personal computers.
A year later, the Intel 8008 appeared. Radio Electronics Magazine reported
that hobbyist Don Lancaster used an 8008 to build what was considered the
first personal computer. The article called it a "TV typewriter."
The Intel 8080 appeared in 1974. It sold then for $400 and now sells for about
$1. It powered traffic lights, but of more interest to our discussion, it formed
the core of the Altair computer of 1975. It was sold in kit form for $395 and
was named for a world in the Star Trek TV series. Figure 4.4 shows a picture
of the 8080 die. By today's standards, it was very weak: 6000 transistors, an
8-bit bus, and a 2-MHz clock speed. It could address 64 K of RAM (random
access memory), and users programmed the Altair by throwing manual
switches located on the case.
Figure 4.4 The Intel 8080 microprocessor
Microprocessor Design
Before going further into the history of microprocessor development, it is
important to discuss in general terms how microprocessors operate.
Microprocessors are usually divided into three subsystems: the control unit
(CU), the arithmetic logic unit (ALU), and the input/output (I/O) unit. The
term CPU is used to denote a combined CU and ALU, contained in a single
package.
The advent of the CU marked a radical improvement in processor design,
allowing CPU operations to be based in part on code provided by an external
program like a BIOS (basic input/output system). This extended the ability of a
PC to use new hardware components that were not part of the original design.
The ALU is just what its name implies—the part of the IC that handles the
basic math functions of computation. The I/O unit fetches data from the
outside and passes data back to the external bus.
Registers
Registers are temporary memory storage areas used during data manipulation.
Physically, registers are rows of microscopic switches that are set on or off.
Each row forms a binary number: off = 0 and on = 1. Hence (reading from
right to left) off.off.on equals the number 1. Off.on.on equals the number
three (0 + 2 + 1). The CPU uses registers, like scratch pads, to hold data while
it works on a task. Changes in data during an operation are also stored in a
register, then sent out to other components as the job is finished. The number
and width of a register vary from one type of machine to another. The wider
the register, the more bits the machine can handle at one time—just as with
the width of the external bus. As register width moved from 4 to 8 to 16 to 32
to 64 to 128 bits, PCs increased in performance.
Codes
Computers use various binary-based codes to represent information. In
Chapter 2, "Understanding Electronic Communication," we saw how ASCII
(American Standard Code for Information Interchange) code is a binary
representation of characters on a keyboard. These codes are sent on the
external data bus by a system component to be read by other devices. When
you press a key on a PC keyboard, an ASCII code is generated and sent over
the data bus. Transferring information to and from the CPU (and other
hardware) is only the first step in manipulating data.
Other codes tell the PC how to display data on the monitor, talk to devices
such as printers, and take in data streams from scanners. Each of those
operations requires system resources and the manipulation of binary numbers.
In addition to the code that requires data, special machine code is required for
the CPU to turn the string of numbers into something useful to an application.
As with the data code, this machine code is sent in the form of binary numbers
on the data bus. The CPUs in turn are different enough that a code system
must be written specifically for each of them.
The Clock
Timing is essential in PC operations. Without some means of synchronization,
chaos would ensue. Timing allows the electronic devices in the computer to
coordinate and execute all internal commands in the proper order.
Placing a special conductor in the CPU and pulsing it with voltage creates
timing. Each pulse of voltage received by this conductor is called a clock cycle.
All the switching activity in the computer occurs while the clock is sending a
pulse. This process somewhat resembles several musicians using a metronome
to synchronize their playing, with all the violinists moving their bows at the
same time. Thanks to this synchronization, you get musical phrasing instead of
a jumble of notes.
Virtually every computer command needs at least two clock cycles. Some
commands might require hundreds of clock cycles to process. Figure 4.5 shows
an external data bus with a CPU and two devices. Notice that the crystal or
clock is attached to the CPU to generate the timing.
Figure 4.5 CPU with clock
Clock Speed
It is common for computers to be marketed to consumers based on features
that show off their best points. One main selling point is the system clock rate,
which is measured in megahertz (MHz), or millions of cycles per second. The
clock rate suggests how many commands can be completed in two cycles (the
minimum time required to execute a command). The process of adding two
numbers together would take about four commands (eight clock cycles). A
computer running at 450 MHz can do about 44 million simple calculations per
second.
Clock speed is determined by the CPU manufacturer and represents the fastest
speed at which the CPU can be reliably operated. The Intel 8088 processor, as
used in the original IBM PC, had a clock speed of 4.77 MHz. Today's processors
have clock speeds that run up to and, in some cases, exceed 750 MHz.
NOTE
Remember that this speed is the CPU's maximum speed. If you
place too many clock cycles on a CPU, it can fail or overheat and
stop working.
The system crystal determines the speed at which a CPU operates. The system
crystal is usually a quartz oscillator, very similar to the one in a wristwatch.
You can find the system crystal soldered to the motherboard. Look for a silver
part, usually with a label that indicates the crystal speed.
IMPORTANT
A computer has two clocks: one to set the speed and timing and a
second clock to keep time for date and time calculations. They are
two entirely different devices.
Memory
The CPU can only hold a limited amount of information. To compensate,
additional chips are installed in the computer for the sole purpose of
temporarily storing information that the CPU needs. These chips are called
RAM (random access memory). The term random access is used because the
CPU can place or retrieve bytes of information in or from any RAM location at
any time. RAM is explored in greater detail in Chapter 7, "Memory."
Address Bus
The word location is italicized in the last paragraph to underscore the
importance of location in PC memory operations. The content of RAM is
constantly changing as programs and the computer itself use portions of it to
note, calculate, and hold results of actions. It is essential for the system to
know what memory is assigned to which task and when that memory is free
for a new use. To do so, the system has to have a way to address segments of
memory and to quickly change the holdings in that position. The portion of the
PC assigned this task is the address bus.
Think of the address bus as a large virtual table in which the columns are
individual bits (like letters) and each row contains a string of bits (making up a
word). The actual lengths of these words will vary depending on the number of
bits the address bus can handle in a single pass. Figure 4.6 shows a table
containing 1s and 0s. Each segment is given an address, just like the one that
identifies a home or post office box. The system uses this address to send data
to or retrieve data from memory.
Figure 4.6 Memory spreadsheet
Like all the other buses in a PC, the address bus is a collection of conductors.
It links the physical memory to the system and moves signals as memory is
used. The number of conductors in the address bus determines the maximum
amount of memory that can be used (memory that is addressable) by the CPU.
Remember that computers count in binary notation. Each binary digit—in this
case, a conductor—that is added to the left will double the number of possible
combinations.
Early data buses used eight conductors and, therefore, 256 (28) combinations
of code, where possible. The maximum number of patterns a system can
generate determines how much RAM the data bus can address. The 8088 used
20 address conductors and could address up to 1,048,576 bytes of memory
locations, or 220. Today's PCs can address a lot more than that, and, in many
cases, the actual limiting factor is not the number of patterns, but the capacity
of the motherboard to socket memory chips. In all cases, the total amount of
memory is the factor of 2X, where X = the number of connectors.
The CPU does not directly connect to the memory bus, but sends requests and
obtains results using the system's memory controller. This circuitry acts as
both postmaster and translator, providing the proper strings of data in the
right order, at the right time, and in a form the CPU can use. As mentioned
before, any write or read action will require at least two clock cycles to
execute. (It can require more clock cycles on systems that do not have
memory tuned to the maximum system clock speed. In that case, the PC will
have to use additional clock cycles while it waits for the memory to be ready
for the next part of the operation.)
Figure 4.7 shows a diagram of the process with the CPU and RAM stack on the
external data bus. The address bus is connected to the memory controller. It
fetches and places data in memory.
Figure 4.7 CPU and RAM
How Microprocessors Work
Current CPUs, such as the Intel Pentium III, are collections of millions of
switches and bus pathways. They operate all kinds of machines, in addition to
PCs, and are found in cameras, cars, microwave ovens, and TVs, among other
things. Here, however, we are interested only in how they work inside a PC.
Let's look at a simple task: adding two numbers such as 2 and 2 together and
obtain-ing their sum (2 + 2 = 4). The CPU can do math problems very quickly,
but it requires several very quick steps to do it. Knowing how a CPU performs
a simple task will help you understand how developments in PC design have
improved PC performance.
When the user pushes a number key (in a program like Calculator, which can
add numbers), the keystroke causes the microprocessor's prefetch unit to ask
for instructions on what to do with the new data. The data is sent through the
address bus to the PC's RAM and is placed in the instruction cache, with a
reference code (let's call it 2 = a).
The prefetch unit obtains a copy of the code and sends it to the decode unit,
where it is translated into a string of binary code and routed to the CU and the
data cache to tell them what to do with the instruction. The CU sends it to an
address called X in the data cache to await the next part of the process.
When the plus (+) key is pressed, the prefetch unit again asks the instruction
cache for instructions about what to do with the new data. The prefetch unit
translates the code and passes it to the CU and data cache, which alerts the
ALU that an ADD function will be carried out. The process is repeated when the
user presses the 2 key.
Next (yes, there's still more to do), the CU takes the code and sends the actual
ADD command to the ALU. The ALU sums a and b are added together after
they have been sent up from the data cache. The ALU sends the code for 4 to
be stored in an address register.
Pressing the equal sign (=) key is the last act the user must execute before
getting the answer, but the computer still has a good bit of work ahead of it.
The prefetch unit checks the instruction cache for help in dealing with the new
keystroke. The resulting instruction is stored, and a copy of the code is sent to
the decode unit for processing. There, the instruction is translated into binary
code and routed to the CU. Now that the sum has been computed, a print
command retrieves the proper address, registers the contents, and displays
them. (That involves a separate flurry of activity in the display system, which
we won't worry about.)
As you can see, a microprocessor must go through many more steps than
human beings do merely to arrive at the conclusion that 2 + 2 = 4. The
computer must execute a complicated sequence to manage the code, place it,
and fetch it from memory; then it has to be told what to do with it. Yet the
result usually appears as fast as you can type the request. You can see that
clock cycles and, hence, processor speed, have a significant effect on
performance. Other issues that affect performance include memory access and
speed, as well as the response time of components such as the display system.
PC Microprocessor Developments and Features
PC microprocessor design grows more complex with each generation, and CPU
packaging keeps changing to provide room for additional features and
operating requirements. Microprocessors have evolved from the 4004
described earlier into today's high-speed Pentiums. Each new processor has
brought higher performance and spawned new technology. Six basic elements
are customarily used to gauge the performance and capability of a CPU design.
Speed. The maximum number of clock cycles measured in MHz. The
higher the speed, the quicker a command will be executed.
Number of transistors. More switches means more computing power.
Registers. The size (in bits) of the internal registers. The larger the
registers, the more complicated the commands that can be processed in
one step.
External data bus. As data bus size increases, so does the amount and
complexity of code (information) that can be transferred among all
devices in the computer.
Address bus. The size of the address bus determines the maximum
amount of memory that can be addressed by the CPU.
Internal cache. The internal cache is high-speed memory built into the
processor. This is a place to store frequently used data instead of sending
it to slower devices (speed is relative in computers) such as RAM and hard
disk drives. It is built into the processor and has a dramatic effect on
speed. We cover cache in more detail later in this lesson.
Intel has held most of the PC CPU market share since the original IBM PC was
introduced. Closely following each new Intel launch, rivals such as Advanced
Micro Devices (AMD) and Cyrix have offered alternative chips that are
generally compatible with the Intel models. This development, in turn, drives
prices down and spurs a new round of CPU design. Another player is Motorola,
a firm that manufactures the microprocessors used in the Apple family of
computers, among others.
Intel's 8086 and 8088: The Birth of the PC
We have already introduced the "pre-PC" CPUs. Now we take a look at the
models that have powered one of the most dramatic developments of the
modern world: the inexpensive, general-purpose computer.
On June 6, 1978, Intel introduced its first 16-bit microprocessor, known as the
8086. It had 29,000 transistors, 16-bit registers, a 16-bit external data bus,
and a 20-bit address bus to allow it to access 1 MB of memory. When IBM
entered the computer business, the 8086 was too powerful (and expensive) to
meet its requirements.
Intel then released the 8088 processor, which was identical to the 8086 except
for an 8-bit external data bus and a slower top clock rate. This meant that 8bit components (more common at the time) could be used for the construction
of PCs, and 8-bit applications written for earlier machines could be converted
for PC use. The following table compares the 8088 and 8086 chips.
Chip
Number of
Transistors
CPU
Speed
(MHz)
Register External Address Internal
Width Data Bus
Bus
Cache
Intel
29,000
8088
4.77-8
16-bit
8-bit
20-bit
None
Intel
29,000
8086
4.77-10
16-bit
16-bit
20-bit
None
The early 8088 processors ran at 4.77 MHz, whereas later versions ran at 8
MHz. The 8086 and 8088 processors came as a 40-pin DIP (dual inline
package) containing approximately 29,000 transistors. The DIP is so named
because of the two rows of pins on either side of the processor, as shown in
Figure 4.8. These fit into a set of slots on a raised socket on the motherboard.
The small u-shaped notch at one end of a DIP-style CPU denotes the end that
has pin 1. During installation, you need to be sure to line it up correctly or you
might have to repeat the process. While this operation is now pretty rare, it
does need to be done once in a while.
Figure 4.8 DIP processor used for 8086, 8088, and 80286 CPUs
NOTE
The 8088 and 8086 are software-compatible—they can run exactly
the same programs (assuming the PCs that use them don't have
other complicating factors). The benefit of using an 8086 is its 16bit external data bus. This allows an 8086-based computer to
execute the same software faster than an 8088 computer with the
same clock speed.
The early IBM personal computers based on the 8086 and 8088 chips featured
16 KB of memory
A cassette tape recorder or a floppy disk drive for program and data
storage
A nongraphics monochrome monitor and Monochrome Display Adapter
(MDA)
Soon, a new industry was born as third-party vendors started manufacturing
add-ons and improved models of the basic design. Graphics cards with color
and better resolution, clocks, additional memory, and peripherals, such as
printers, extended the features of the new appliance. "Clones" offered some of
these extras at very competitive prices, as a way to attract buyers who wanted
a lower price and did not need the comfort of purchasing from a large company
like IBM.
NOTE
Clone is a computer term that was used in the heyday of the early
IBM PCs through the 386. It denoted a computer that contained
the same microprocessor and ran the same programs as a better
known, more prestigious, and often more expensive machine.
Most of the 8088- and 8086-based PCs used some variation of MS-DOS. The
variations limited the growth of the software market because of the
compatibility issues they presented among versions of MS-DOS. Buyers had to
be sure that a program would run on their specific version of MS-DOS.
As users found more ways to take advantage of the PC's power, developers
and owners alike soon felt the limitations of the original IBM PC design. The
engineers who created it never envisioned the need for more than 16 K of
RAM. "Who would ever need more than that?" one was quoted as saying. The
cassette drive was never a big seller; most buyers opted for one or two 5.25inch floppy disk drives, and many soon craved color graphics and the space of
the seemingly massive 5- and 10-MB hard disk drives.
To meet that growing demand, IBM introduced a more robust PC, the XT
(eXtended Technology), which could take advantage of a hard disk drive. It
came with either a monochrome or four-color display and more RAM. Clone
makers soon followed suit.
The 80286 and the IBM PC AT
In February 1982, Intel introduced the 80286 6-MHz microprocessor (later
pushing clock speeds to 10 and 12.5 MHz), commonly called the 286, with a
24-bit address path. In 1983, IBM unveiled its PC AT (Advanced Technology)
computer, based on the 286. It had a larger, boxier design and it came with a
standard hard drive and a new expansion slot format, rendering older add-on
cards obsolete.
The AT could run the same applications as the PC XT (8088), but run them
faster. The use of a 24-bit address path allowed the 286 to access up to 16 MB
of memory. The clone makers soon followed suit, taking advantage of thirdparty versions of the 286. Chip makers Harris and AMD produced versions of
the 286 that could run at up to 20 MHz.
Computers based on the 80286 chip featured
Two memory modes (real and protected)
16 MB of addressable memory
Clock speeds of up to 20 MHz
A reduced command set (fewer program commands to do more work)
Multitasking abilities
Virtual memory support
Virtual Memory
Virtual memory is the art of using hard disk space to hold data not
immediately required by the processor; it is placed in and out of RAM as
needed. Although using virtual memory slowed the system down (electronic
RAM is much faster than a mechanical hard drive), it allowed the 286 to
address up to 1 gigabyte (1 GB = 1000 MB) of memory (16 MB of actual
memory and 984 MB of virtual memory). Virtual memory required the use of
operating systems more advanced than MS-DOS, leading to the development
of products such as Microsoft Windows, IBM OS/2, and SCO's (Santa Cruz
Operation) PC version of UNIX.
Real Mode vs. Protected Mode
The 286 might have outdated older hardware, but Intel had no desire to
invoke industry ire and slow the adoption of the new chip by requiring all-new
software applications. The result was a CPU with two operating modes: real
and protected.
In real mode, sometimes called compatibility mode, a 286 emulates the 8086
processor and addresses only the first 1 MB of memory. This mode is used to
run older software. Protected mode allows access to all memory on the system,
physical and virtual. In protected mode, a program can write only to the
memory allocated to it, with specific memory blocks allocated to different
programs. This mode can go well beyond the 16 MB of "true" memory, opening
up the possibility of multitasking—running more than one program at a time.
This development required new, more powerful operating systems and
applications, but they were slow in coming. By the time they arrived on the
market, the 286 was functionally obsolete, but it paved the way for today's
powerful multitasking environments such as Microsoft Windows 95, Windows
98, Windows NT, and Windows 2000. Another major drawback to the 286's
memory management scheme was its need to reboot the system when
changing between real and protected modes.
The original 286 processor came packaged in DIP (already shown), pin grid
array (PGA), and PLCC (plastic leadless chip carrier) designs. The PLCC can be
recognized by the arrangement of thin legs around its perimeter. The PLCC's
major advantage is its stronger leads (pins), which make it more difficult to
damage during removal or installation. PLCCs became popular because they
made it easier to upgrade a PC with a faster CPU (see Figure 4.9).
Figure 4.9 PLCC CPU package
The 80386 Arrives
On June 16, 1985, Intel introduced the original 80386 (commonly known as
the 386). This true 32-bit processor was equipped with a 32-bit external data
bus, 32-bit registers, and a 32-bit address bus. The first models shipped with a
clock speed of 16 MHz, and the CPU contained 275,000 transistors. It could
directly address 4 GB of RAM and 64 terabytes (TB = approximately 1 trillion
bytes) of virtual memory. According to Intel, the 386 could hold an eight-page
history of every person on earth in that address space. The 386 was a true
generational leap in PC computing, with true multitasking capability—it really
could run more than one program at a time. That was due to a third memory
mode, called virtual real mode, which allowed independent MS-DOS sessions
(called virtual machines) to coexist on the same system at once. It spawned a
host of programs called memory managers designed to optimize (and
troubleshoot) the more complex world of virtual memory.
The original 80386 chips shipped with speeds of 12 or 16 MHz. Intel produced
faster versions—25 and 33 MHz—and AMD manufactured a 40-MHz variant.
The 386 provided both the real and protected mode available in the 286.
By April 1989, the 386 was running at clock speeds of 33 MHz, and Intel was
calling it the 80386DX to distinguish it from a lower-cost model, the 386SX.
The 386SX: A Scaled-Down Version
The 386SX came on the scene in June 1988. Intel wanted to increase the sales
of 386-based machines without dramatically dropping the price of its flagship
CPU. The result was the introduction of a scaled-down model for "entry-level"
computers. It had a 16-bit external data bus and a 24-bit address bus (it could
address only 16 MB of memory). The 16-bit configuration allowed the 386SX
to be used as an upgrade chip for existing 16-bit motherboards, thereby
providing an easy transition to the next generation of computers.
The following table compares members of the 80386 chip family from Intel and
rival AMD. The AMD 80386DXLV is notable as the first PC CPU with an internal
cache.
Chip
CPU
External
Number of
Register
Address Internal
Speed
Data
Transistors
Width
Bus
Cache
(MHz)
Bus
Intel
80386SX
275,000
16-25
32-bit
16-bit
24-bit
None
Intel
80386DX
275,000
16-33
32-bit
32-bit
32-bit
None
AMD
80386DX
275,000
20-40
32-bit
32-bit
32-bit
None
AMD
80386DXL
275,000
20-33
32-bit
32-bit
32-bit
None
AMD
275,000
80386DXLV
20-33
32-bit
32-bit
32-bit
8 KB
NOTE
The terms SX and DX are not acronyms, which means that they do
not stand for longer terms.
386 Packaging
The 386 was usually placed in either a PLCC package or a PGA package. This
type of mount can be found with the 80386, 486, and some older Pentiums up
to the 166-MHz models. The pins are evenly distributed in concentric rows
along the bottom of the chip (see Figure 4.10).
Figure 4.10 PGA
PGA chips go into regular PGA or the popular ZIF (zero-insertion-force)
sockets. You will probably never have to contend with either mount today, but
if you do, keep the following in mind. Care must be used when inserting or
removing CPUs from a PGA mount—it is very easy to bend the pins if you do
not pull perfectly straight up from the socket or have a slight uneven push
downward. ZIF mounts are a bit better, but much technician time has been
wasted straightening pins, and it is possible to ruin a CPU. PGA mounts are
often "hidden" under a CPU fan, which presents another hurdle during repair
or upgrade.
A variation of the PGA is the staggered pin grid array (SPGA). It looks almost
the same, but with staggered rows of pins. This allows engineers to place more
connectors in a smaller area. It also adds emphasis to the caution given earlier
about not bending pins through careless removal or insertion.
Both the PGA and SPGA have three pointed corners and a "snipped corner" on
one side. Use that corner to align the chip with the socket. If it does not go in
smoothly, double-check before trying to force it!
Laptop Designs and the Plastic Quad Flat Pack
Some forms of portable PC have existed from the days of the 8088. The early
models, such as the Osborne and the original Compaq, were known as
"luggables"—tipping the scales at close to 30 pounds. Their cases looked more
suited for holding sewing machines than computers. Modern laptop computers
started to gain popularity with the advent of the 386 chip and the use of flatscreen monitors incorporated in the design, rather than conventional video
tubes (see Chapter 11, "The Display System," for more information).
To seat 80286, 80386, and 80486 CPUs (the latter are covered in the section
that follows) on the more compact laptop motherboards, many vendors use
plastic quad flat pack (PQFP) mounts, which are also more secure than
traditional socket types designed for systems that will not be moved as much.
PQFPs require a submount called a carrier ring (see Figure 4.11). PQFPs
require a special tool for placing or removing a CPU. Be sure to get the tool
before attempting repairs on PQFP-mounted CPUs.
Figure 4.11 PQFP
80486
On April 10, 1989, Intel introduced the 80486 line of processors. Once again,
the rallying cry was "better and faster." By this time, applications like
CorelDRAW and Adobe PhotoShop, and desktop publishing tools like Aldus
PageMaker and Ventura Publisher were generating more interest in faster
systems. Microsoft Windows was gaining popularity on its way to becoming the
standard desktop environment.
The 486 processor started life at 25 MHz and could address 4 GB of RAM and
64 TB of virtual memory. It is the first PC CPU to break the 1-million transistor
mark with 1.2 million. It provided a built-in math coprocessor (older PC CPUs
offered separate math coprocessors as an option, usually with a similar
number ending in a 7 rather than a 6. The combination speeded up graphics
programs that used floating-point math).
The 486SX and Beyond
Once again, Intel sought a way to increase sales without weakening the price
of the flagship version of its 486DX CPU, so it added an SX version in April
1991. This time, the company achieved its goal by removing the math
coprocessor, reducing the number of transistors to 1,185,000. Users could
upgrade the SX to a 486DX by adding an optional OverDrive processor to
restore the missing component.
The 486 label was attached to other chip designs during its active development
phase, both by Intel and third-party chip makers. The 486SL, a variant with a
20- to 33-MHz clock and 1.4 million transistors, debuted in 1992. It was very
popular in high-performance laptop computers, running at lower voltage (3.3
volts instead of 5 volts) than the usual 486. The small and (for that time)
powerful machines also included System Memory Management (SMM) mode,
which could dim the liquid crystal display (LCD) screen and power down the
hard disk drive, extending the life of the battery.
System Memory Management
SMM is a hardware-based function that allows the microprocessor to
selectively shut down the monitor, hard drives, and any other peripherals not
in use. SMM works at the chip level; the microprocessor can be operating in
real, protected, or virtual 8086 mode. SMM is transparent to all software
running on the system, which decreases the likelihood of lockups.
Clock-Doubling Debuts
The need for speed spurred the introduction of new models of the 486 family
through the spring of 1994, the last variations being the DX2 and DX4. These
chips were models with faster clock speeds of up to 100 MHz. The processors
were either 25- or 33-MHz versions that had been altered to run internally at
double or triple their external speed. For example, the DX4 version of the 486
33-MHz processor ran at 33 MHz externally, but at 100 MHz internally (3 ×
33.3 MHz). This meant that internal operations, such as numeric calculations
or moving data from one register to another, occurred at 100 MHz, whereas
external operations, like loading data from memory, took place at 33 MHz.
Slower external clock speeds allowed existing motherboard and memory
designs to be used. Upgrades were less expensive, and new machines based on
the DX technology could quote faster benchmarks at lower costs. The DX4
offered 16 KB of on-board cache, further boosting performance. The DX2 50MHz-based machines should not be confused with machines designed around
the 50-MHz 486DX processor—the latter performed much better.
Vendors such as AMD rode the wave with their own editions of the 486 for
users with a need for greater speed. The following table lists the most popular
486 chips and third-party work-alikes.
Chip
CPU
Speed
(MHz)
Register
Width
External
Data Bus
Address Internal
Bus
Cache
Intel 80486DX
25, 33, 50
32-bit
32-bit
32-bit
8 KB
Intel
80486DX/2
50, 66
32-bit
32-bit
32-bit
8 KB
Intel
80486DX/4
75, 100
32-bit
32-bit
32-bit
16 KB
Intel 80486SX
16, 20, 25
32-bit
32-bit
32-bit
8 KB
Intel 80486SL
16, 20, 25
32-bit
32-bit
32-bit
8 KB
AMD AM486DX
33, 40
32-bit
32-bit
32-bit
8 KB
AMD
AM486DXLV
33
32-bit
32-bit
32-bit
8 KB
AMD AM486DX2 50, 80
32-bit
32-bit
32-bit
8 KB
AMD AM486DX4 100, 120
32-bit
32-bit
32-bit
8 KB
16 KB
AMD AM486DX
"Enhanced"
AMD
AM486DXL2
120, 133
32-bit
32-bit
32-bit
writeback
50, 80
32-bit
32-bit
32-bit
8 KB
AMD AM486SX
33, 40
32-bit
32-bit
32-bit
8 KB
AMD
AM486SXLV
33
32-bit
32-bit
32-bit
8 KB
AMD AM486SX2 33
32-bit
32-bit
32-bit
8 KB
32-bit
8 KB
writeback
32-bit
8 KB
writeback
32-bit
1 KB
writeback
32-bit
1 KB
writeback
32-bit
1 KB
writeback
CYRX CX486DX
CYRX
CX486DX2
CYRX
CX486DLC
CYRX
CX486SLC
CYRX
CX486SLC2
33
50-80
33-40
20-33
50
32-bit
32-bit
32-bit
32-bit
32-bit
32-bit
32-bit
32-bit
32-bit
32-bit
NOTE
Write-through and write-back caches are explained in Chapter 7,
"Memory."
Heat Sinks and Fans
The 486 is notable for one other reason: the addition of a standard heat sink
and, usually, a fan mounted on the CPU and powered by the PC. To maintain
stable operation, the PC must provide proper cooling for the 486 and newer
CPUs. Failure of the cooling apparatus can lead to erratic behavior and, if left
uncorrected, can damage the chip. If a customer complains of strange noises
inside the PC, the CPU fan is a good place to check. As their bearings age, CPU
fans may start to whine.
The First Pentiums
By 1993, Windows was standard, and users expected a lot more from PCs in
performance and features. Increasing software sophistication led to increasing
memory usage and hard disk drive requirements. The market was ready for a
major upgrade in CPUs, and Intel once again addressed that need. The new
Pentium processor signaled a radical redesign of both the CPU and naming
conventions.
With its CPUs identified by numbers, Intel faced a business problem: Numbers
cannot be trademarked. The company's strategy was to substitute a name that
could be trademarked, Pentium, for its upcoming chips that would otherwise
have been named 586. The word is based on the Latin word for the number
five, and this chip would have been the 80586. The original design has been
revamped several times since 1993 with the introduction of the Pentium II in
1997, the Pentium III in 1999, and the Pentium 4 in 2000. Like the older PC
CPUs, the Pentium has spawned its share of clones, leading to entry-level PCs
priced under $400.
The Pentium (Series I) offered the following features:
Speeds of 60 MHz to greater than 200 MHz.
32-bit address bus and 32-bit registers.
64-bit data path to improve the speed of data transfers.
Dual pipeline, 32-bit data bus that allows the chip to process two separate
lines of code simultaneously.
At least an 8-KB write-back cache for data and an 8-KB write-through
cache for programs. (Types of caches are explained in more detail in
Chapter 7, "Memory.")
Branch prediction, in which the program cache attempts to anticipate
branching within the code. The CPU stores a few lines of code from each
branch so that when the program reaches the branch, the Pentium
already has the code stored within the cache.
The following table lists the first generation of Pentium and Pentiumcompatible chips.
Chip
Speed
(MHz)
Register External Address
Width Data Bus
Bus
Internal Cache
Intel
Pentium
60, 66
32-bit
64-bit
32-bit
Intel
Pentium
75
32-bit
64-bit
32-bit
Intel
Pentium
Intel
Pentium
Intel
Pentium
Intel
Pentium
90, 100
120, 130
150, 166
180, 200
32-bit
32-bit
32-bit
32-bit
Cyrix 6x86 100, 120,
32-bit
(P-rating) 133, 200
AMD K5
(P-rating)
75, 90
32-bit
64-bit
64-bit
64-bit
64-bit
64-bit
64-bit
8 KB write-back
and 8KB writethrough
8 KB write-back
and 8KB writethrough
32-bit
8 KB write-back
and 8KB writethrough
32-bit
8 KB write-back
and 8KB writethrough
32-bit
8 KB write-back
and 8KB writethrough
32-bit
8 KB write-back
and 8KB writethrough
32-bit
8 KB write-back
and 8 KB writethrough
32-bit
8 KB write-back
and 8 KB writethrough
NOTE
Write-through and write-back caches are explained in Chapter 7,
"Memory." P-rating is a standard method of rating chips by their
equivalency to a Pentium chip. It avoids direct comparison of clock
speeds. Each processor is tested on an identical system and
measured accordingly. If a chip performs 1.5 percent slower than a
Pentium chip, it gets the same rating as the next lower chip.
Mass-producing reliable Pentium 66 (P66) chips proved difficult, and many
were rejected during quality control. The faulty chips were stable at clock
speeds of 60 MHz, so Intel sold them as the P60. Some users change their P60
processor clock speed to 66 MHz by changing a jumper on the motherboard.
Although this might have worked, it made computer performance and
longevity unpredictable.
Intel continued to use the 0.8-micron manufacturing process (the ability to
draw lines as fine as 1/1000 of a millimeter on the die, about 16,000 lines per
inch), begun with the 486, to fit 3.1 million transistors on the Pentium chip.
The P66 used considerable power and consequently generated a large amount
of heat. Operating a reliable heat sink and fan became critical with the advent
of the Pentium.
The Pentium 75 was released in 1994. These chips were made using a 0.6micron manufacturing process (approximately 21,000 lines and spaces per
inch) and, as a result, they required considerably less power, despite an
additional 200,000 transistors. Intel was able to change the power supply from
5 volts to 3.3 volts (the DX4 also had a reduced power supply), which reduced
by nearly one-half the amount of heat produced. The P90 and P100 processors
were also released at this time. These processors ran internally at 1.5 times
the external speed (60 or 66 MHz, which was the fastest system board). A P75
processor was also released for use in lower specification machines and laptop
computers.
Superscalar Technology
The main components of a processor—registers, decoders, and ALUs—are
collectively known as the instruction pipeline. To carry out a single instruction,
a processor must
Read the instruction
Decode the instruction
Fetch operands (for math functions)
Execute the instruction
Write back the results
Early processors carried out these steps one at a time. Combining these steps
into a single clock cycle, a process known as pipelining, thereby increases the
speed of processing. Superscalar technology allows the Pentium to have two
instruction pipelines—called U and V. The U pipeline can execute the full range
of Pentium instructions, whereas the V pipeline can execute a limited number.
When possible, the Pentium processor breaks up a program into discrete tasks
that are then shared between the pipelines, allowing the Pentium to execute
two simple instructions simultaneously. Software must be specifically written
to take advantage of this innovative feature, which is known as multithreading.
Pentium On-Board Cache
The original Pentium series came with two 8-KB caches—one for data and one
for program code—compared with the single 8-KB cache on the 486 (16 KB on
the DX4). As described with the 486 chip, the cache uses a technique called
branch prediction to improve its ability to guess what data or program code
will be required next by the processor.
Intel's Competitors
Competitors have moved away from simply making clones of the Intel
processors. They are currently designing their own processors with unique
features. AMD and Cyrix are among the best known. Until recently, all the
Intel processors had been based on a CISC (complex instruction set
computing) architecture. Processors based on RISC (Reduced Instruction Set
Computing) have been used in high-powered machines since the mid-1980s.
Intel has produced its own version of a RISC-based processor that uses a much
smaller and simpler set of instructions, greatly enhancing the speed of the
processor.
Pentium Pro
Intel made CPU selection even more complex with the introduction of the
Pentium Pro in 1995, offering varied features, in different models, of the
Pentium design. This processor was aimed at a 32-bit server and workstationlevel applications such as CAD (computer-aided design), mechanical
engineering, and advanced scientific computation. The Pentium Pro was
packaged with a second speed-enhancing cache memory chip, and it boasted
5.5 million transistors. Introduced in November 1995, it incorporated an
internal RISC architecture with a CISC–RISC translator, three-way superscalar
execution, and dynamic execution. While compatible with all the previous
software for the Intel line, the Pentium Pro is optimized to run 32-bit software.
Its pin structure and mount differ from the basic Pentium, requiring a special
ZIF socket. Some motherboards have sockets for both Pentium and Pentium
Pro chips, but most machines use mother-boards designed for one or the
other. The package, a 2.46-inch by 2.66-inch 387-pin PGA configuration,
houses a Pentium Pro processor core and an on-board L2 cache. Although
mounted on one PGA device, they are two ICs. A single, gold-plated copper
and tungsten heat spreader gives them the appearance of a single chip.
The main CPU and 16-KB first-level (L1) cache consist of 5.5 million
transistors; the second chip is a 256- or 512-KB second-level (L2) cache with
15 million transistors. A 133-MHz Pentium Pro processes data about twice as
fast as a 100-MHz Pentium.
One reason for the better performance is a technology called dynamic
execution. Before processing, the data flow is analyzed and sequenced for
optimal execution. Then the system looks ahead in the program process and
predicts where the next branch or group of instructions can be found in
memory, processing up to five instructions before they are needed. By using a
technique known as data-flow analysis, the Pentium Pro can determine
dependencies among data items so they can be processed as soon as their
inputs are available, regardless of the program's order.
Pentium MMX
Soon, more choices were on the way. About the time the 166-MHz Pentiums
shipped, Intel introduced MMX (Multimedia Extension) technology, designed to
enhance performance of data-hungry applications like graphics and games.
With larger data and code caches, Pentiums with MMX technology can run nonMMX-enhanced software approximately 10 to 20 percent faster than a nonMMX CPU with the same clock speed.
To reap the full benefits of the new processor, MMX-enhanced software makes
use of 57 special multimedia instructions. These new MMX operators use a
technology called SIMD (single-instruction multiple-data) stream processing.
SIMD allows different processing elements to perform the same operations on
different data—a central controller broadcasts the instruction to all processing
elements in the same way that a drill sergeant would tell a whole platoon to
"about face," rather than instruct each soldier individually.
The MMX chips also take advantage of dynamic branch prediction using the
branch target buffer (BTB) to predict the most likely set of instructions to be
executed.
The MMX Pentium processor is also more compatible with older 16-bit software
than is the Pentium Pro; consequently, it soon doomed the Pro to the
backwaters of PC computing. All later versions of the Pentium have
incorporated some variation of MMX and improved on it. The original Pentium
desktop line ended with the release of the 233-MHz MMX in June 1997.
Pentium II
By 1997, multimedia was becoming mainstream, and high performance in a
graphical user environment was critical to CPU market success. Intel upped the
ante for its competitors in 1997 with a radical redesign. The first 233-MHz,
7.5-million-transistor, Pentium II processor incorporated MMX technology and
was packaged with a high-speed cache memory chip (see Figure 4.12). Intel
released Pentium II versions operating at speeds of up to 450 MHz. This period
also marked the introduction of the 100-MHz system bus.
The Pentium II incorporated the features of its older designs and added a
number of enhancements, including:
Multiple branch prediction. Predicts program execution through several
branches, accelerating the flow of work to the processor.
Data-flow analysis. Creates an optimized, reordered schedule of
instructions by analyzing data dependencies among instructions.
Speculative execution. Carries out instructions speculatively and, based
on this optimized schedule, ensures that the processor's superscalar
execution units remain busy, boosting overall performance.
Single-edge connector (SEC) cartridge packaging. Developed by
Intel, this enables high-volume availability and offers improved handling
protection and a common form factor for future high-performance
processors. This development eliminated problems caused by pins
accidentally bent during installation or removal of CPUs.
High-performance Dual Independent Bus (DIB) architecture.
System bus and cache bus.
System bus that supports multiple outstanding transactions to
increase bandwidth availability. It also provides "glueless" support for
up to two processors. This enables low-cost, two-way symmetric
multiprocessing, providing a significant performance boost for
multitasking operating systems and multithreaded applications. Many
inexpensive motherboards offer two Slot 1 sockets, making it easy to
build a dual processor system for use with operating systems like
Windows NT or Windows 2000.
512-KB unified, nonblocking, L2 cache. Improves performance by
reducing average memory access time and providing fast access to
recently used instructions and data. Performance is enhanced through a
dedicated 64-bit cache bus. The speed of the L2 cache scales with the
processor core frequency. This processor also incorporates separate 16KB, L1 caches, one for instructions and one for data.
Models available in 450, 400, and 350 MHz. Support memory caches
for up to 4 GB of addressable memory space.
Error-correction coding (ECC) functionality on the L2 cache bus.
For applications in which data intensity and reliability are essential.
Pipelined FPU (floating-point unit). Supports the 32-bit and 64-bit
formats specified in IEEE (Institute of Electrical and Electronics
Engineers) standard 754, as well as an 80-bit format.
Parity-protected address/request and response system bus
signals. Includes a retry mechanism for high data integrity and
reliability.
Variations on a Theme: The Intel Celeron CPUs
As it had in the past, Intel faced competitors who sold CPUs with similar
performance at lower prices. Most high-priced desktop computers and servers
were sold with a Pentium of one sort or another, but home and entry-level PCs
were another matter. Enter a variation of the SX concept—the Celeron.
Celeron models available in 500, 466, 433, 400, 366, and 333 MHz have
expanded Intel processing into the market for computers selling for less than
$1,200.
All the Intel Celeron processors are available in PGA packages. The versions
operating at 433, 400, 366, 333, and 300 MHz are also available in singleedge processor packages (see Figure 4.12).
Key features include the following
MMX media enhancement technology.
Dynamic Execution Technology.
A 32-KB (16-KB/16-KB) nonblocking, L1 cache for fast access to heavily
used data.
Celerons operating at 500, 466, 433, 400, 366, and 333 MHz include
integrated 128-KB L2 cache.
All Celeron processors use the Intel P6 microarchitecture's
multitransaction system bus at 66 MHz. Processors at 766, 733, 700,
667, 633, 600, 566, 533, 500, 466, 433, 400, 366, and 333 MHz use the
Intel P6 microarchitecture's multitransaction system bus with the addition
of the L2 cache interface.
Like the Pentium family, the Celerons offer multiple branch prediction,
data-flow analysis, and speculative execution.
Figure 4.12 Intel Pentium II in a SEC package
Xeon: The Premium Pentium
Intel has labeled a new CPU brand to denote high-end server and highperformance desktop use. First introduced in June 1998, the Xeon line
commands a premium price and offers extra performance-enhancing
technology. The Pentium II models incorporate 7.5 million transistors, clock
speeds to 450 MHz, bus speeds of 100 MHz, full-speed L2 caches in varying
sizes up to 2 MB, new multiprocessing capabilities, and compatibility with
previous Intel microprocessor generations. All models use the SEC package.
Pentium III Processor
The Intel Pentium III processor is the newest member of the P6 family. With
28 million transistors, speeds from 450 MHz to 1 GHz, and system bus speeds
of 100 to 133 MHz, they mark a significant jump in PC CPU technology. They
employ the same dynamic execution microarchitecture as the Pentium II—a
combination of multiple branch prediction, data-flow analysis, and speculative
execution. This provides improved performance over older Pentium designs,
while maintaining binary compatibility with all previous Intel processors. The
Pentium III processor, shown in Figure 4.13, also incorporates MMX
technology, plus streaming SIMD extensions for enhanced floating-point and
3-D application performance. It also utilizes multiple low-power states, such as
AutoHALT, Stop-Grant, Sleep, and Deep Sleep to conserve power during idle
times.
Figure 4.13 The Intel Pentium III processor
Intel offers a Xeon version of the Pentium III processor at speeds up to 1 GHz,
aimed at high-performance workstations and servers.
Motorola
Motorola has been the mainstay CPU for Apple computers. The 68000
processor was introduced in 1979 as a 32-bit chip with a 16-bit data path. At
that time, the 68000 outperformed the Intel 8086. In 1982, the 68010
arrived, adding virtual memory support and a cache capable of holding three
instructions.
1984 saw the advent of the Macintosh II-series computer, which used the
68020 processor. It was the first full 32-bit chip, with a 32-bit data path, math
coprocessor, and the ability to access up to 4 GB of RAM. Introduced in the
same year as Intel's 80286 processor, the Motorola ran faster. However, it
lacked the market share and third-party support to gain real marketplace
momentum. PC clones offered more programs at a lower cost than the Apple
offerings.
The 68030 chip, introduced in 1987, provided increased data and instruction
speed. This was comparable to the 80386 chip. The 68040 processor was
introduced (in the Macintosh Quadra) as a competitor to the 80486. It has
internal caches for data and program code.
The PowerPC processor was developed jointly by IBM, Motorola, and Apple. The
name stands for performance optimization with enhanced RISC. The chips in
this family of processors are suitable for machines ranging from laptop
computers to high-powered network servers. It can run MS-DOS software
without using emulation.
Lesson Summary
The following points summarize the main elements of this lesson:
The microprocessor is the centerpiece of today's computers.
Understanding the development and progression of the processor is
essential in understanding how to mix older technology with new
technology.
The three key elements that go into measuring a CPU's performance are
its speed, address bus, and external data bus.
The development of the 80286 processor introduced the concepts of real
and protected modes and allowed the use of up to 16 MB of memory.
The development of the 80386 processor brought about 32-bit processing
and allowed up to 4 GB of memory.
The 80486 processor is a "souped-up" version of the 80386 that
introduced the use of cache memory.
The Pentium chip began a new line of processors and technology,
incorporating RISC and true multithreading capabilities in an Intel
microprocessor for the first time.
Pentium MMX technology was developed to meet the needs of today's
multimedia world.
The Intel Pentium III further extended PC performance with advanced
cache technology and streamlined code handling.
Several players are currently competing with Intel for the processor
market (NextGen, AMD, Cyrix, IBM), but Intel has the largest market
share by far.
Today's standard processor is the Pentium III, with processor speeds of
500 MHz and faster.
3 4
Lesson 2: Replacing and Upgrading a CPU
A computer technician is commonly expected to upgrade computers. Because
the CPU is the "brain" of a computer, replacing this single component can bring
new life to an aging system. Replacing the chip is easy, but understanding the
possible scenarios for a successful upgrade can be more challenging.
After this lesson, you will be able to
Decide whether a CPU is worth upgrading
Find the type of CPU required for upgrade
Install a new CPU
Estimated lesson time: 15 minutes
Replacing a CPU can be very simple, but it is important to first carefully
consider whether to do so. If you do decide to replace it, you will need to take
care to avoid damaging the chip during installation. Before undertaking this
process, always ask yourself, "What CPUs can be put on this motherboard?"
The best source for an answer is the documentation packaged with the
computer or motherboard. If the motherboard manual is not available and you
do not have a reference, the document should be available on the
manufacturer's Web site.
Possible Upgrade Scenarios
There are a number of issues to think about when deciding whether to upgrade
a CPU or replace a machine altogether. Perhaps the most important issue is
the value of the upgrade. Will the suggested upgrade meet the operational
requirements for that computer? There are limits to what can be upgraded and
the results that can be expected from the upgrade. A poor upgrade can lead to
total failure and could ultimately require replacement of the motherboard.
Again, the best source of information regarding CPU upgrades is the
documentation that comes with the motherboard. The following table lists
several possible scenarios for upgrading a CPU.
Existing
CPU
Recommendation
8086/8088 Cannot be upgraded.
80286
through
486
Replace the system. It may be possible to use isolated
components, but not worth the effort.
80386SX
Same as for 80286. Replace the motherboard.
Pentium I
Replace a Pentium I motherboard, display adapter, and
sound card with newer components. Depending on the
customer's needs and budget, you may save floppy drives,
mouse, and other minor components.
May upgrade either just the CPU or CPU and motherboard,
depending on the system, the case, and the BIOS. In the
Pentium II case of AT-style PCs, you may need to change the case to an
ATX form factor, and upgrade the motherboard, keyboard,
and mouse to newer designs.
Pentium
III
Possible to just upgrade CPU; it may require a new
motherboard if the CPU is not supported by the chip set.
On average, it is more cost-effective to replace an entire motherboard than it
is to upgrade a CPU. However, you have to judge for yourself. Make sure that
the new motherboard will fit into the computer case (check size and alignment
of expansion buses) before starting the installation. Be sure that the power
supply of the old case and new motherboard are of the same type with the
proper connectors (such as AT, ATX). Always make sure that you can return a
CPU and mother-board to the vendor if they won't fit. Be sure to determine
this before you open the packaging or attempt to install the components. Keep
in mind that many suppliers charge a restocking fee of 15 to 20 percent for
returns.
Inserting a CPU
There are several types of CPU sockets available. Today virtually all desktop
PCs come with some variation of the SEC packaging. Other CPUs are generally
not worth upgrading and may be one of two common types of package:
Low-insertion-force (LIF)
Zero-insertion-force (ZIF)
NOTE
You may encounter a situation where a person wants to hand off
an older computer to a relative or friend who does not have a
computer. For completeness, we have included information on
these older form factors. You will rarely encounter machines older
than a 486, and most of your experience will be with Pentiumclass machines.
LIF Socket
Removing an old CPU from an LIF socket is a muscular business! Luckily, there
are special tools designed for this. However, a flat-head screwdriver or a plate
cover for an expansion card slot will also work—just be sure to pry evenly
around the CPU or you will risk damaging the CPU, the socket, or both.
NOTE
There is a notch in one corner of an LIF socket. The CPU will also
have a notch and a dot in one corner, designed to help align the
CPU correctly. The index corner of the CPU must line up with the
notch on the socket. Firmly press the CPU into the PGA socket,
making sure all the pins are lined up.
ZIF Socket
The ZIF socket, shown in Figure 4.14, was the most popular mount for desktop
and tower PCs with 486 and early Pentium CPUs.
Figure 4.14 ZIF socket with CPU inverted showing matching pins
A ZIF socket has a lever arm that allows for simple removal and installation of
CPUs. ZIF sockets were introduced during the early 1990s as a safe means of
providing a user-friendly CPU upgrade. The first ZIF socket had 169 pins and
was used on 486SX systems. These systems were sold with a 486SX chip
already installed in a PGA socket and provided a ZIF socket for a 486
OverDrive chip, a special processor designed to increase the speed of 486
computers. (It works much like the standard clock-doubling processors—DX2
and DX4—used on 486 motherboards.) Often, this is a good method of
increasing the speed of a computer without replacing the motherboard.
The following table describes the types of ZIF sockets.
CPU Type
Number of
Pins
Pin
Layout
Voltage
486SX/SX2, DXUDX2, DX4ODPR
169
17 × 17
PGA
5v
SX/SX2, DX/DX2, DX4ODPR,
Pentium OverDrive
238
19 × 19
PGA
5v
SX/SX2, DX/DX2, DX4ODP, Pentium
OverDrive
237
19 × 19
PGA
5v/3.3v
Pentium 60/66
273
21 × 21
PGA
5v
Pentium 75/90/100/120
320
37 × 37
SPGA
3.3v
486 DX4, Pentium OverDrive
235
Pentium 75-200
321
19 × 19
PGA
21 × 21
SPGA
3.3v
VRM
NOTE
ODPR stands for overdrive processor replacement. PGA is a pin
grid array. SPGA is a staggered pin grid array, and VRM is a
voltage regulator module.
Care When Handling a CPU
Be very careful when handling a CPU or any exposed IC. Static discharge can
damage or ruin the chip. Be sure to use a wrist-grounding strap or other
approved antistatic device. Take great care to not bend any pins, and make
sure the CPU is properly lined up to seat Pin 1 by using the code notch.
CAUTION
If you encounter any resistance, stop at once and determine what
is wrong.
Check the memory and bus speed required for the new CPU before attempting
to boot the PC after the procedure. It might require new RAM and will most
often demand that a jumper be set on the motherboard before operating at the
new speed.
SEC Package/Slot 1 Upgrades
The Pentium II and III series are most commonly packaged in an SEC. This
package, shown in Figure 4.15, is very simple to work with. You will need a
motherboard mount and might have to purchase a fan and heat sink before
installing the CPU. Check the manual for jumper-setting adjustments and
follow the simple directions that come with the CPU.
Figure 4.15 Pentium processor in an SEC package and Slot 1
The actual task involves seating two plastic pins, sliding two guides over the
sides of the CPU, and then pushing the frame and CPU into the slot on the
board. With dual CPU boards, you need to know which slot to use, and you
might have to place a special card (which comes with the motherboard) in the
second CPU position if it is to remain empty.
CAUTION
Be sure to properly mount the cooling system, and make sure the
fan works before running the new CPU for any amount of time or
closing the case. Failure to ensure proper heat removal will
destroy the CPU very quickly!
Lesson Summary
The following points summarize the main elements of this lesson:
Replacing a CPU is usually a simple task.
It is important to consider the limitations and potential of an upgrade
before deciding to replace a CPU.
Be very careful of electrostatic discharge (ESD) and potential pin damage
when handling a CPU.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter.
Microprocessors
The CPU—a microprocessor—is the centerpiece of today's computers.
Clock speed is only one determining factor in identifying overall
performance of a processor.
Processors are generally defined by their speed, the size of the external
data bus, and the size of the address bus.
The development of the 80286 processor introduced the concepts of real
and protected modes and allowed the use of up to 16 MB of memory.
The development of the 80386 processor brought about 32-bit processing
and allowed up to 4 GB of memory.
The 80486 processor is a "souped-up" version of the 80386 and it
introduced the use of cache memory.
The Pentium chip began a new line of processors and technology,
incorporating RISC and true multithreading capabilities in an Intel
microprocessor for the first time.
The Pentium II chip further extended the power of the PC and introduced
a new packaging method that made handling the CPU and performing
upgrades much simpler.
The Intel Pentium III further extended PC performance with advanced
cache technology and streamlined code handling.
Today's standard processor is the Pentium III, with processor speeds of
500 MHz and faster.
Replacing and Upgrading Chips
It is important for a computer technician to know the technological
advances made by each successive generation of computers.
Simply upgrading the CPU can often lengthen the life span of a computer.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. What is the language of the computer?
2. What is an external data bus?
3. Describe an integrated circuit (IC).
4. Define a clock cycle.
5. What are the advantages of a Pentium processor over a 486?
6. What is the difference between SX and DX in a 386 chip?
7. Which computers use the Motorola 68040 chip?
8. Define microprocessor.
9. In computer code language _________ means on and _________ means
off.
10. Define clock speed.
11. What is the function of the address bus?
12. Microprocessor chips (CPUs) are manufactured in a variety of sizes and
shapes. Name as many different kinds as possible.
13. Name the basic types of CPU sockets.
14. If a customer brought you an old Pentium 60-based computer and asked
you to install a new processor, what would your advice be?
Answers
3 4
Chapter 5
Power Supplies
About This Chapter
The power supply is an often-underrated part of a computer. Many transient
problems can be related to a faulty power supply or to poor electrical supply
from the local provider. Electronic components require a steady electrical
current, free of surges or drops. The power supply is responsible for providing
clean, constant current.
Before You Begin
No specialized knowledge is required; however, a fundamental understanding
of terms related to power and electricity such as voltage and wattage is helpful
when learning about power supplies.
3 4
Lesson 1: Power Supplies
This lesson presents basic information about power supplies for computer
systems. We take a look at the different variations of power supplies, how to
identify the proper type, and how to connect it to the computer (both
motherboard and related devices). We also examine the safety considerations
related to working with power supplies. As a certified computer technician, you
will often be called on to troubleshoot, identify, and replace power supplies.
After this lesson, you will be able to
Define the current and voltage requirements for a computer power supply
Identify when you need to replace a power supply
Specify the correct surge suppressors for a computer system
Select a backup power supply for a computer system
Estimated lesson time: 15 minutes
Overview of Power Supplies
A standard power supply draws power from a local, alternating current (AC)
source (usually a wall outlet) and converts it to either 3.3 or 5 volts direct
current (DC) for on-board electronics, and 12 volts DC for motors and hard
drives. In all cases, it delivers both positive and negative DC to the computer.
Power supplies must "condition" the power, smoothing out any radical changes
in its quality. Many homes and offices have power that fluctuates far more
than the delicate parts of a PC can tolerate and survive under. Most PC power
supplies also provide electricity to the system's cooling and processor fans that
keep the machine from overheating.
If the computer's power supply is providing reliable, clean power and its own
cooling fan works, all is well. If the power supply or its fan should fail or cause
erratic behavior by the PC, the power supply must be replaced. (Although it is
possible to remove and replace a power supply fan, the low cost of a power
supply makes it more practical to replace the power supply itself.)
Most supplies have a universal input that will accept either 110 volts
alternating current (VAC), 60 hertz (Hz) (U.S. standard power), or 220 VAC,
50 Hz (European and Asian standard). When replacing a power supply, there
are three things to consider: physical size, wattage, and connectors. The
remainder of this chapter covers the basics of power supplies.
NOTE
A hertz is a measure of unit frequency: 1 cycle per second equals
1 hertz. A kilohertz (kHz) is 1,000 cycles per second; a megahertz
(MHz) is 1 million cycles per second.
Power Supply Sizes
Power supplies are available in a few standard sizes and shapes. However, the
names for power supplies are anything but standard. They are based on the
type of case in which they are installed and the types of motherboard
connections they will support. This is because different styles of cases place
items such as plug fittings, mounting screws, and fans in different places, and
motherboard styles offer different connections and placement of plugs. These
cables and fittings must be compatible to work together.
The very first PCs all used the same type of power supply with a large, red
switch on the side. Variations were manufactured for early portables and tower
cases, with longer or shorter cables and different types of switches. They all
shared a common pair of motherboard connectors. Collectively they are known
as AT-style. When replacing an AT-style power supply, you generally only need
to be concerned about the type of case that it will go in. The exceptions are
some high-end network servers, which sometimes allow for an extra power
lead to the motherboard. All newer desktop PCs (Pentium II and later) and
servers use ATX-style power supplies. The ATX design simplifies motherboard
connection by combining the two power leads in the AT-style power supply into
one. The main issues to be aware of are how much wattage the PC needs to
power its parts and how many peripheral connectors are required. Generally
speaking, older Pentium-based computers and all 486-based and earlier PCs
used AT-style supplies; almost all Pentium II and later-based systems use ATXstyle supplies. The ATX design is preferable for two reasons:
The on–off power control circuit (not the button) on ATX boards is built
into the motherboard. On AT-style PCs, it comes from the power supply.
AT-style power supplies connect to the motherboard through a pair of sixwire connectors. ATX-style power supplies connect through a single 20pin connector.
A few motherboards and power supplies provide both AT and ATX fittings and
switch support. These are rare, but provide more options should you have to
repair such a system. Generally, you should use ATX-style power supplies for
all replacements, if possible.
When replacing a power supply, it's a good idea to compare the existing power
supply to the new one. Make sure that they are physically the same size, have
the same connectors, and that the new one has at least the same power
rating. Some high-quality power supplies offer "silencer" fans that are much
quieter than most models.
Power Supply Wattage
Power supplies are rated according to the maximum sustained power
(measured in watts) that they can produce. A watt is a unit of electrical power
equivalent to one volt-ampere. It is important to keep in mind that the power
supply must produce at least enough energy to operate all the components of
the system at the same time.
You can determine a computer's power consumption by adding the power
requirements, measured in watts, for all the devices in the unit. When
evaluating a power supply, however, don't rely on the computer's operating
consumption alone. Remember that a much larger drain occurs as the machine
powers up, when hard drives and other heavy feeders simultaneously compete
for the available startup power. Most general-use computers require 130 watts
while running and about 200–205 watts when booting (at startup). Sound
cards, modems, and (worst of all) monitors attached with an accessory plug in
the case can push a weak power supply to its limit and beyond.
Servers and high-performance workstations often have an abundance of
random access memory (RAM), multiple drives, SCSI (Small Computer System
Interface) adapters, and power-hungry video cards, along with one or more
network cards. They often demand power supplies of 350–500 watts.
CAUTION
The label on a power supply that says "Don't Open" means just
that! Opening a power supply is dangerous. It is better to
completely remove and replace a defective power supply as
needed.
Power Supply Connectors
Power supplies employ several types of connectors, all of which are easy to
identify and use. On the outside of the computer enclosure, a standard male
AC plug and three-conductor wire (two power wires and a ground) draws
current from a wall outlet, with a female connection entering the receptacle in
the back of the power supply. There are three types of connectors on the
inside: the power main to the motherboard (which differs, as mentioned, in AT
and ATX models) and two types of four-pin fittings to supply 5 volts and 3.3
volts of power to peripherals such as the floppy disk and hard disk drives. Let's
take a close look at each in turn.
AT-Style Connections to the Motherboard
A pair of almost identical connectors, designated P8 and P9, links the power
supply to the motherboard (see Figure 5.1). These connectors are seated into
a row of six pins and matching plastic guides, or teeth, on the motherboard.
The P8 and P9 connectors must be placed in the proper orientation. The
motherboard manual will show which fittings are for P8 and P9. If the
connectors are not marked,
Figure 5.1 P8 and P9 connectors and motherboard fitting
make sure that the two black wires on each plug are side by side and that the
orange wire (on P8) and the two red wires (on P9) are on the outside as you
push them into place.
The following table of power cables shows voltage values for each of the colorcoded wires on P8 and P9. The ground wires are considered 0 volts; all voltage
measurements (see Chapter 22, "The Basics of Electrical Energy") are taken
between the black wires and one of the colored wires.
Cable Color
Supply In
Tolerance
Yellow
+12
±10%
Blue
–12
±10%
Red
+5
±5%
White
–5
±5%
Black
Ground
N/A
NOTE
Some computer makers employ proprietary power connections
that require a special power supply. To install a new part in these
types of computers, you will need to follow the instructions that
come with the computer.
Remember to install the P8 and P9 plugs so that the black wires are side by
side. Installing them on the wrong receptacle can damage both the
motherboard and the power supply. Figure 5.2 shows the P8 and P9
connectors and a motherboard.
NOTE
Some power supplies have a third P-style connector. This is used
only on very few motherboards and it can be ignored on those on
which it is found. If you come across one, refer to the manual that
came with the part for instructions on its requirements and
installation.
Figure 5.2 Connecting P8 and P9
ATX-Style Motherboard Connections
The newer ATX main power connection, found on Pentium II computers and
later, is much easier to install. A single 20-pin plug is set into a fitted
receptacle and secured with a catch on the side of the plug that snaps over the
fitting. Figure 5.3 shows how to properly seat the connection. A small, flat-tip
screwdriver is a handy tool for easing the pressure on the catch to remove the
plug. In some cases, you can use a screwdriver to ease installation as well.
Figure 5.3 Placing an ATX plug in its motherboard receptacle
Connections to Peripheral Hardware
Two standard types of connectors are used to connect the power supply to
peripheral hardware:
Molex connector. This is the most commonly used power connector. It
provides both 12-volt and 5-volt power. Hard disk drives, internal tape
drives, CD-ROM drives, DVD (digital video disc) drives, and older 5.25inch floppy disk drives all use this fitting. The Molex connector has two
rounded corners and two sharp corners to ensure that it installs properly
(see Figure 5.4).
Figure 5.4 Molex connector (not to scale)
Mini connector. Most power supplies provide one or more mini
connectors (see Figure 5.5). The mini is used primarily for 3.5-inch floppy
disk drives. It has four pin-outs and, usually, four wires. Most are fitted
with keys that make it difficult, but not impossible, to install upside down.
Be sure to orient the connector correctly; applying power with the
connector reversed can damage or destroy the drive.
Figure 5.5 Mini connector (not to scale)
Two- and Three-Pin Mini Plugs
A less common type of power connector is used to connect the fan of a
Pentium II or III processor to the motherboard for power, to connect a CDROM drive to a sound card, and to provide power for 3.5-inch floppy disk
drives. These connectors have two or three wires that are usually red and
black or red, yellow, and black.
CAUTION
Do not connect power-carrying mini plugs to audio or data devices
such as a CD drive or a sound card, because you could damage or
destroy those devices.
Extenders and Splitters
PCs can run out of power connections, and large cases can have drives beyond
the reach of any plug on the supply. A good technician has a quick solution on
hand to both of these common problems: extenders and splitters.
Extenders are wire sets that have a Molex connector on each end; they are
used to extend a power connection to a device beyond the reach of the power
supply's own wiring. Splitters are similar to extenders, with the exception that
they provide two power connections from a single power supply connector.
Lesson Summary
The following points summarize the main elements of this lesson:
Power supplies come in a variety of sizes and shapes.
There are two types of main power connectors: AT and ATX.
A power supply must be capable of handling the requirements of the
computer and all internal devices.
Be careful when attaching some connectors; if connected incorrectly, they
can damage the computer.
Do not open the power supply housing!
Keeping a few splitters and extenders in the repair kit can help the
technician easily solve some common problems.
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Lesson 2: Power Supply Problems
Power supply problems can come from both internal and external sources.
Component failure within a computer can cause a power supply to fail, but the
most common failures come externally from the power source itself. In this
lesson, we look at common problems associated with power supplies and what
you, as a technician, can do about them.
After this lesson, you will be able to
Determine the types of problems that can be caused by power supplies
Know when to check and when to replace a power supply
Plan how to protect your system from external power supply problems
Estimated lesson time: 10 minutes
Power Failures
Power supplies are affected by the quality of the local power source. Common
power delivery problems such as spikes, surges, sags, brownouts, and
blackouts affect the stability and operation of the main power supply and are
passed on to the computer. Although most users don't notice sudden changes
in the quality of electrical power, computers and other sensitive electronics are
affected. Although we can't fully control these problems, there are a few things
we can do, noted in the following table, to protect our equipment and data and
ensure a reasonably clean electrical supply.
Problem
Description
Surges
These are brief (and sometimes catastrophic) increases in the
voltage source (very high voltage for a very short time). They
can originate with the power source (the local power
company) but most often are due to lightning strikes.
Spikes
Spikes are very short overvoltage conditions. Spikes are
measured in nanoseconds, whereas a surge is measured in
milliseconds.
Sags
These are brief decreases of voltage at the power source.
If a sag lasts longer than 1 second, it is called a brownout.
The overloading of a primary power source can cause
Brownouts brownouts. Some brownouts are "scheduled" by power
companies to prevent overloading of circuits and potential
catastrophic failure of the system.
Blackouts
A blackout is a complete power failure, which can be caused
by equipment failure (local or regional) or accidental cutting
of power cables. When the power returns after a blackout,
there is a power spike and the danger of a power surge.
Power Protection Devices
Surge suppressors are devices used to filter out the effects of voltage spikes
and surges that are present in commercial power sources and smooth out
power variations. They are available from local computer dealers and
superstores. A good surge suppressor will protect your system from most
problems, but if you purchase an economy model, it might not work when you
need it most. Keep in mind that almost nothing will shield your hardware from
a very close lightning strike.
NOTE
Most power strips with surge protection have a red indicator light.
If the light goes out, this means that the unit is not providing
protection. These types of surge suppressors need to be replaced
every year or so. If the indicator light starts flashing before then,
it means the power strip is failing and should be replaced
immediately.
When evaluating the quality of surge suppressors, look for performance
certification. At a minimum, it should have an Underwriters Laboratory (UL)
listing and power ratings. A high-quality unit will also provide protection for
phone/fax/ modem and network connections. These units protect up to a
point; however, for complete protection from power fluctuations and outages,
an uninterruptible power supply (UPS) is recommended.
A UPS is an inline battery backup. When properly installed between a
computer and the wall outlet, a UPS protects the computer from surges and
acts as a battery when the power dips or fails. It also provides a warning that
the power is out of specification (above or below acceptable levels). Many
models can also interact with the computer and initiate a safe shutdown in the
event of a complete power failure using software that runs in the background
and sends a signal through one of the computer's COM ports when the power
goes down.
The amount of time that a UPS device can keep a system running is
determined by battery capacity and the power demands of the equipment
connected to it. A more powerful UPS device will need its own line and circuit
breaker. One of the principal power drains is the monitor. To keep a system
online as long as possible during a power failure, turn off the monitor
immediately after the failure commences.
When considering a UPS, take into account how much protection is needed, as
well as the importance of peace of mind to the user. The VA rating (voltage ×
amps = watts) must be sufficient to supply the computer and all its peripherals
with power for enough time to safely shut down the system. The easiest way
to calculate this number is to add the power rating (watts) for all pieces of
equipment that are to be connected to the UPS, as shown in the following
table.
Power Rating
(Watts)
Device
Connected to
UPS
Power
Required
Computer
200–350
Yes
250
Monitor
80–100
Yes
80
External modem
5.5
No
0
External backup
drive
50
Yes
50
Total
335.5–505.5
—
380
CAUTION
Never plug a laser printer into a UPS unless the UPS is specifically
rated to support that type of device. Laser printers often require
more power than a UPS is able to provide, potentially placing the
printer, the UPS, and the computer at risk.
Power Supply Problems
The most easily recognized problem is a complete failure of the power supply.
This is easy to detect because, in the event of a failure, the computer will not
boot up (no lights, no sound). If there is apparently no power, be sure to check
the power source and the plug at both ends: the outlet and the computer.
If you are experiencing intermittent failures such as memory loss, memory
corruption, or unexplained system crashes, don't rule out the power supply—it
is often the culprit. Fortunately, it is easy to check and replace.
Good power supplies have line-conditioning circuits, but these might not be
sufficient in locations where the power source has substantial quality flaws. If
you have problems with several systems, or if a second power supply still does
not fix a related complaint, add a UPS with good line-conditioning features.
Most power grids in the United States provide current that is far from ideal for
sensitive electronic components. Line-conditioning hardware added in the
chain just before the current reaches the machine adds a much needed level of
protection from spikes (very fast jumps in power levels), surges (longer ones),
and drops. All can cause transient problems with operations. These are often
erroneously blamed on the operating system or software.
Lesson Summary
The following points summarize the main elements of this lesson:
Power supply problems can be caused by component failures within the
power supply or from the power source.
Two devices protect against external power problems: surge suppressors
and UPSs.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Power Supplies
The key to specifying the proper size of a power supply for a computer is
to add together the power requirements for all the components. It is
important to be sure to add extra power to allow for boot up.
Electrical power is measured in watts.
Proper installation of the P8 and P9 connectors is important to prevent
damage to the motherboard. The black (ground) wires must be installed
side by side.
Molex and mini connectors are used to connect power to devices such as
floppy disk and hard disk drives.
Power Supply Problems
The flow of power into a computer must be managed to prevent damage
and/or loss of data.
Surge suppressors will protect against higher-than-normal voltage
problems.
High-quality UPS devices will protect a computer from most power
fluctuations.
Check power supplies when there are unusual problems with memory and
PC operations that do not have a reasonable cause.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Explain the differences among spikes, surges, and sags.
2. What are the two types of power supply connectors to the motherboard?
3. What are the two types of power supply connectors for devices such as
drives?
4. Name two benefits of having a UPS on a system.
5. Describe the difference between a brownout and a blackout.
6. When you purchase a UPS, what is the most important thing to consider?
7. Will any surge suppressor provide protection against lightning strikes?
8. What is the best defense against spikes caused by lightning?
9. What is the most important thing to remember when connecting a P8 and
P9 connector to a motherboard?
10. Explain the difference between the mini connector and the Molex
connector.
11. Describe the best way to make sure a new power supply matches the one
you are replacing.
12. What is the primary use of mini connectors?
13. A computer power supply has both 5-volt and 12-volt outputs. The 5-volt
output is used to power _____________, and the 12-volt output is used
to power _____________.
Answers
3 4
Chapter 6
Motherboard and ROM BIOS
About This Chapter
In earlier lessons, we provided an overview of the computer. In this chapter,
we focus on the computer's infrastructure. We begin with the centerpiece of
the computer, the motherboard, also called the mainboard. The motherboard is
the key part of the hardware infrastructure. It is a large circuit board that
serves as a home for the central processing unit (CPU) and all its associated
chips, including the chip set and RAM (random access memory), and connects
them to the rest of the physical elements and components of the computer.
Before You Begin
Although this chapter can be studied independently, it is suggested that you
review the preceding chapters, which discuss microprocessors, basic
input/output, and how power gets to the system, before reading this material.
3 4
Lesson 1: Computer Cases
The case, or chassis, which usually is made of metal, holds all the primary
electronics of the personal computer (PC) and often all the drives as well.
After this lesson, you will be able to
Identify the primary types of PC cases
Explain how the case helps to protect the PC and surrounding devices
from electromagnetic interference
Estimated lesson time: 5 minutes
The Computer Case
To casual users, the PC is a metal container, attached by a few cables to a
keyboard, mouse, and monitor. In fact, the case is more than just a box to
house a computer.
The real value of a case does not lie in the label, color, or how pretty it looks.
Instead, the case houses all the internal components, offers access to the
outside world via ports and connectors, and protects the PC's delicate circuits
from damage and electromagnetic interference (EMI). It also protects
surrounding devices, such as TVs, from the PC's EMI.
NOTE
Electromagnetic interference (EMI) is a newer term for radio
frequency interference (RFI). EMI is any radio frequency that is
emitted from an electrical or electronic device that is harmful to
the surrounding equipment or that interferes with the operation of
another electrical or electronic device. A computer interferes with
radio, telephone, or TV reception when it generates EMI. Any highquality computer will contain special circuits and grounding to
prevent emissions from escaping into the surrounding area.
Running a computer without its cover is a sure way to generate
EMI.
The case design is also often used to underscore the identity of a specific brand
of computer, and can often be part of the reason we purchase a particular
computer. Some people will also choose a case design for its appearance. We
do, after all, want something that looks good, especially if we are spending a
lot of money on it. With some cases, however, there may be a more technical
reason for the case choice, such as the number of drive bays available.
Early computer cases were little more than boxes that sat on the desk and
served as monitor stands. Today, some manufacturers build "designer"
computers that come in fancy colors and command premium prices.
As computer technicians, we don't usually concern ourselves with the
computer case; we simply deal with whatever our customer uses. However,
when it comes to recommending a computer for purchase, the size and
configuration of the case should be considered. Depending on the business
application, the difference between a tower and a desktop design can be
important.
When considering the case, there are four general rules to keep in mind:
The bigger the box, the more components it can hold (providing greater
expansion potential) and, often, the better the air flow (essential for
cooling). Large cases are also easier to work with.
The more compact the box, the less expansion potential it has; working
on it is often much more difficult, and usually air flow is more restricted.
Smaller cases that come with a power supply usually have lower wattage,
reducing the number of internal devices that can be installed.
The more features in a case design, like the power wattage or the number
of bays, the higher the cost.
IMPORTANT
It is not a good idea to run a computer for extended periods of
time with the case open or removed entirely. This not only
produces EMI, but also results in improper air flow and reduced
cooling of the system components. If you must do so, consider
placing a small fan so that it blows an air stream over the CPU and
chip set.
Working with Cases
In any repair job that involves inspecting or replacing internal components,
the technician has to open the case. That used to be very simple; the
technician would remove four screws in the back of the computer with a
Phillips screwdriver, then pull the case's cover forward to reveal the contents.
Today, however, cases come in a variety of forms, with screws in the front or
back, fancy plastic bevels in front, and featuring one of several types of metal
wraps—some in several parts, some in a single piece.
The majority of cases still open the old-fashioned way. However, if you find
yourself with one of the exceptions and can't locate screws in the back, check
to see if the plastic cover in the front can be pulled off. If so, that should
reveal three or four screws. Then see if the main cover can be pulled forward.
If not, look for screws that secure one or more of the side panels. Some side
panel designs are great for granting easy access to our next topic,
motherboards. This style of case allows one to inspect or remove the
motherboard without having to remove the entire outer covering.
Another trend is a case design using fittings that can be opened without any
tools. Some computers now provide easy opening with a thumb screw that
doesn't even require a screw driver. If you are working with one of these
computers, simply turn the thumb screw and slide the case back.
Lesson Summary
The following points summarize the main elements of this lesson:
The case of the PC defines the size, shape, and configuration of the
motherboard, the amount of expansion possible, and the space into which
hard drives and other internal accessories can be fitted.
To prevent EMI and ensure system components are properly cooled, you
should avoid running a computer without its cover.
3 4
Lesson 2: Motherboards
The motherboard is the PC's center of activity. All devices in a computer are in
some way connected to the motherboard. It hosts the largest single collection
of chips of any PC component and serves as the "street system" for the grid of
wires that link all the components, making it possible for them to
communicate.
After this lesson, you will be able to
Identify a motherboard and its functions
Locate and define the components of a motherboard
Safely remove and replace a motherboard
Estimated lesson time: 15 minutes
The Motherboard
The motherboard (one is shown in Figure 6.1) defines the computer's limits of
speed, memory, and expandability. A computer needs more than just a CPU
and memory. To accept input from the user, it needs devices, such as a
keyboard and a mouse. It also needs output devices, such as monitors and
sound cards, to cope with the powerful graphics and sound capabilities of the
programs available today. A computer also needs "permanent" storage devices,
such as floppy disk drives and hard disk drives, to store data when it is turned
off. It is the function of the motherboard to provide the connectivity for all
these devices, as well as for the CPU, RAM, and support integrated circuits
(ICs).
Figure 6.1 Motherboard with CPU
The motherboard is usually the largest circuit board found inside the computer
case. Motherboards come in a variety of shapes. One size does not fit all, and
careful attention to size and location of mounting holes is required before
installing a new motherboard in an older computer. A motherboard needs to fit
in the space allotted for it, be secure in its mounts, be properly grounded,
receive sufficient ventilation (for cooling of the CPU and other heat-sensitive
components), and must not conflict with other hardware. When considering
the purchase of a new motherboard (see Lesson 2 of Chapter 4, "The Central
Processing Unit"), keep these things in mind:
Most "generic" motherboards will fit into "generic" computers. One reason
some people consider purchasing a PC clone is that it is easier to upgrade.
Keep in mind that a hybrid PC (assembled by a small vendor, made from
untested components) may be constructed of parts that may or may not
be totally compatible. There may also be questions about EMI due to
interaction between components or the way the parts set in the case.
There are two major categories of motherboards: AT and ATX. The main
difference between them is the type of power supply and main power
switch each requires. When you order a new motherboard, be sure to first
verify that it is compatible with the case and power supply to be used.
If you are working on a brand-name computer, you might be required to
purchase a new motherboard or other custom components from the same
manufacturer.
Before buying a motherboard, check its technical references to be sure
that the new board will fit and will be compatible with any of the RAM and
expansion cards the owner intends to use. Often, this information can be
found in the owner's manual. If not, check the manufacturer's Web site, if
one is available, or check other online resources such as technical
libraries. A Web search using the keyword "motherboard" will yield sites
dedicated to computer hardware.
For all practical purposes, you cannot repair motherboards. They should
be replaced if physically or electrically damaged. Your customer will get
new technology, usually for a price lower than the cost of the repair.
Because it is often the most difficult part of a system to replace (you have
to remove all the equipment that is connected to it), check all other
internal and external components before removing or replacing the
motherboard.
When obtaining a replacement, be sure to factor in the cost of all critical
options found on the existing motherboard. Some have a built-in SCSI
(Small Computer System Interface) Host Adapter or display adapters that
might not be common. In that case, either make sure the new board
offers the same level of support or install the appropriate add-on card(s)
to bring the system up to the existing level of operation.
Chip Sets
A motherboard comes with a variety of support chips soldered in place. The
primary elements constitute the chip set and are designed to work with the
CPU. These chips are highly complex and coordinated ICs that help the CPU
manage and control the computer's system. When replacing a CPU, you must
make sure that it is compatible with the chip set and supported by the
motherboard. If not, the computer won't work. A basic chip set (see Figure
6.2) consists of a
Bus controller
Memory controller
Data and address buffer
Peripheral controller
Figure 6.2 Motherboard with chip set
On modern motherboards, you will find specialized chips to control things such
as cache memory and high-speed buses. You will also find boards with fewer
individual chips because the manufacturer has incorporated several functions
into one chip.
Keep in mind that there is a wide range of features (with attendant cost
increases for extras) available when selecting a motherboard. You will need to
keep up to date on the types of processors, memory design, CPUs, and
expansion slots available to recommend and obtain the right product for your
customers.
Be careful in choosing motherboards with components like display adapters
and sound cards on board. These are components that may not have all the
features of their expansion card versions, and customers may decide to
upgrade, leaving them with motherboard-based elements that could cause
conflicts.
Lesson Summary
The following points summarize the main elements of this lesson:
Motherboards come in many sizes and shapes, but generic boards are
available that fit most clone computers.
The motherboard determines the limits of the computer's capabilities.
Chip sets are unique to each motherboard design and work with the CPU
to manage and control the computer's system.
You should make sure any new motherboard is compatible with the CPU,
RAM, and any other critical hardware and features that are already
installed on the computer.
3 4
Lesson 3: ROM BIOS
In addition to the chip set, you will find other chips called ROM BIOS. A ROM
BIOS chip contains data that specifies the characteristics of hardware devices,
such as memory and hard disk and floppy disk drives, so the system can
properly access them. This lesson explores ROM BIOS and what it does.
After this lesson, you will be able to
Identify the different types of ROM
Modify the CMOS settings in a computer
Identify POST codes and take appropriate corrective action when a
problem is identified
Estimated lesson time: 30 minutes
ROM BIOS
ROM (read-only memory) is a type of memory that stores data even when the
main computer power is off. This is necessary so that the system can access
the data it needs to start up. When stored in ROM, information that is required
to start and run the computer cannot be lost or changed. The BIOS (basic
input/ output system) is software in the form of programs stored on ROM
chips. The system BIOS is a ROM chip on the motherboard used by the
computer during the startup routine (boot process) to check out the system
and prepare to run the hardware. The BIOS is stored on a ROM chip because
ROM retains information even when no power is being supplied to the
computer. The downside of storing data in an older computer's ROM is that a
chip may have to be changed to update information.
More recent systems use a technology called flash ROM or flash BIOS that
allows code in the core chips to be updated by software available through the
BIOS or motherboard supplier. Check the Internet site of the supplier if you
suspect your ROM chip has flash ROM technology; the software and
instructions are generally downloadable.
CAUTION
Upgrade a BIOS only when necessary! Be sure to follow all
precautions included with the motherboard manual and
instructions for the upgrade. Improper installation can render the
motherboard useless.
BIOS (also referred to as firmware) can be subdivided into three classes,
depending on the type of hardware it controls.
The first class, called core chips, includes support for hardware that is
common to all computers, is necessary, and never changes.
The second class, called updateable chips, encompasses hardware that is
also common and necessary, but that might change from time to time.
The third class of chips includes anything that is not included in one of
the first two classes.
Core Chips
Look on any motherboard: ROM chips for the core chips are found everywhere.
They are often distinctive because they are in DIP (dual in-line package) form
and are almost always labeled. These chips are commonly used for the
keyboard, parallel ports, serial ports, speakers, and other support devices.
Each ROM chip contains between 16 and 64 KB of programming. If the
functions have been combined, it may be harder to determine the chip's
purpose by appearance.
Updateable Chips
Several devices on a computer often contain their own flash BIOS or
updateable ROMs including SCSI controllers and video cards. Because this
information is subject to change (for instance, you can upgrade a hard disk
drive or change a video card), it is stored on a special chip called the
complementary metal-oxide semiconductor (CMOS). This chip gets its name
from the way it is manufactured and what it is made from, not from the
information it holds.
Unlike other ROM chips, CMOS chips do not store programs, but instead store
data that actually configures the features of the motherboard. For example, it
notes the number of floppy drives, the type(s) of hard drives, and if powersaving options or administrator passwords are active. The CMOS chip also
maintains date and time information when power to the computer is off.
CMOS chips can store about 64 KB of data. However, storage of the data
needed to boot a computer requires only a very small amount of memory
(about 128 bytes).
If the data stored on the CMOS is different from the hardware it keeps track
of, the computer, or part of it, will probably not work. For example, if the hard
disk drive information is incorrect, the computer can be booted from a floppy
disk, but the hard disk drive might not be accessible. The technician or owner
will have to reset the CMOS values before the computer can use the device if
it is not properly defined in the CMOS registry.
The information contained in a CMOS chip will depend on the manufacturer.
Typically, the CMOS contains at least the following information:
Floppy disk and hard disk drive types
CPU
RAM size
Date and time
Serial and parallel port information
Plug and Play information
Power-saving settings
IMPORTANT
It is critical that the core information on a CMOS chip be correct. If
you change any of the related hardware, the CMOS must be
updated to reflect those changes. If the CMOS loses power from its
battery, it will lose its data. The next time the system is started,
the setup program will revert to its default settings. It is a good
idea to write down the primary system settings (like hard drive
parameters) and tape them inside the case for reference.
Updating CMOS
To make changes to a CMOS chip, you need to run a CMOS setup program.
This application is independent of the operating system, because it must work
even if an operating system is not loaded, or even if there is no form of disk
drive. The way to start this program depends on the manufacturer of the
BIOS, not the manufacturer of the computer. Manufacturers of motherboards
purchase the BIOS from other companies, most of which specialize in making
these chips. Many different computer suppliers use the same BIOS. The BIOS
manufacturer and version number are the first things you see displayed when
you boot up your computer. Figure 6.3 shows examples of startup information
for three different types of BIOS chips.
Figure 6.3 BIOS information
Although several companies write BIOS code and sell it to computer makers,
three companies—American Megatrends (AMI), Phoenix, and Award—dominate
the BIOS market. Motherboard vendors might use one supplier for a series of
products; however, it is not uncommon for a manufacturer to change sources
within a series due to design or cost considerations. A good technician should
be familiar with the basic CMOS setup procedures for BIOS manufactured by
all three.
Because of its flexibility, the Hi-Flex BIOS, manufactured by AMI, has taken a
large share of the computer market. Motherboard manufacturers can purchase
a basic BIOS from AMI and then add setup parameters to meet the needs of
their products. For this reason, the number of setup parameters available on
one computer can differ from those on another computer, even though they
use the same motherboard. Award competes directly with AMI, providing very
flexible BIOS chips. Award was the first BIOS to heavily support Peripheral
Component Interconnect (PCI) motherboards.
Phoenix is considered a manufacturer of high-end BIOS. Phoenix creates
individual BIOS chips for specific machines. As a result, Phoenix BIOS chips
have fewer setup parameters available. These chips are commonly used in
machines with proprietary motherboards, such as laptops. Vendors can tune
the BIOS for performance, basing new code on the Phoenix core. Keep in mind
that Phoenix also makes parts that are sold and employed without custom
code.
There are several ways to determine who the BIOS manufacturer is:
Watch the monitor when the computer boots. A BIOS screen will usually
be displayed, indicating the manufacturer and version number. (This
screen might not be visible if the computer is warm booted. In that case,
power off the unit and restart.)
Check the computer or motherboard manual. Most include a section on
entering the setup program and setting options.
Remove the cover of the computer and look at the chip. Most BIOS chips
have a manufacturer's label.
Try a good third-party utility program. These products are available at
almost any software store. A Web search for a key phrase such as "BIOS
diagnostic" will yield the names of a number of them.
Reboot the computer and hold down several keys at once or unplug a
drive. This will often cause an error and prompt you to get into the setup
program. Unplugging the keyboard will accomplish the same goal with
less work; however, you won't be able to make adjustments on most
systems with the keyboard inoperative.
A Typical CMOS Setup
Every CMOS setup program looks slightly different. Do not be too concerned
about the differences—all BIOS routines contain basically the same
information. Take your time and get comfortable navigating in the setup
programs. Most of the CMOS setup programs are text-based, so you will have
to use keystrokes to navigate through the information. However, some newer
machines use a Windows-like CMOS setup (they have the look of a Windows
environment and will let you use a mouse to select changes).
The Most Common Ways to Access BIOS Setup Programs
For AMI, press Delete when the machine first begins to boot.
For Phoenix, press Ctrl+Alt+Esc, Del, or F2 when requested.
For Award, you can usually follow either of the other two procedures.
Motherboard makers can change the key combinations to access the CMOS
setup. This can be especially true for brand-name computers, and
manufacturers are not likely to publish the information on the startup screen.
TIP
If all else fails, try any of these key combinations: Ctrl+Alt+Insert,
Ctrl+A, Ctrl+S, Ctrl+F1, F2, and F10.
Let's look at some typical screens from a Phoenix BIOS setup program. They
are good examples of how typical CMOS settings are presented and adjusted.
Figure 6.4 shows the first screen of this CMOS setup. From this point, you can
select alternate tabs (Advanced, Security, Power) or adjust any of these
individual items: floppy disk drive, hard disk drive, date and time, or RAM
settings.
Figure 6.4 Main screen
The hard disk drive setup screen (Figure 6.5) is where individual hard drive
parameters are set. Today, most hard drives based on IDE (Integrated Device
Electronics) can be automatically detected by the BIOS. The CMOS settings are
then made by the BIOS automatically. However, you should still know how to
do this manually, both to be able to work with an older machine and in case
the setup program fails to recognize the drive.
Figure 6.5 Hard disk drive setup screen
The Advanced tab (Figure 6.6) leads to more advanced setup parameters. A
great deal of customization can be achieved using these settings. Pay careful
attention to any warnings that come up before you make any changes to
device settings. If you don't understand a setting, it is best to leave the default
option.
The Security tab allows you to set security parameters. Be careful: Once you
set a password, you have to remember that password to change the security
parameters. If you encounter a situation in which an owner has set and
forgotten a password, you will have to flush and reset the CMOS to the factory
default settings. Check the motherboard manual for information on how to do
this. It usually involves changing jumper settings twice.
Figure 6.6 Advanced tab
Notice in Figure 6.7 that the virus check reminder option is disabled. If you
find a CMOS virus checker enabled, turn it off. This is especially important
during operating system and program installation. If you are certain that no
virus software is on the computer, yet you continue to get error messages
warning you to turn off all anti-virus software, the CMOS virus checker is the
most likely source of these erroneous messages. If you find this happening,
disable the CMOS virus checker. Of course, if you still get the message, you
should check for a real virus. Figure 6.7 shows the Security tab.
TIP
These built-in CMOS virus checkers actually do very little to
protect your system. For the best possible protection against
viruses, be sure to install a good anti-virus program designed for
the operating system on the computer and suggest that the
customer run and update it regularly.
Figure 6.7 Security tab
The Power tab, shown in Figure 6.8, allows the user to set up any power
conservation options provided by the manufacturer. These features typically
include setting a time limit for reducing power to the monitor and hard disk
drive.
Figure 6.8 Power tab
Maintaining CMOS
Losing CMOS information is, unfortunately, a common problem. If the
information on the CMOS chips is erased or corrupted, the computer will not
be able to boot or you will get nasty-looking errors. Some of the more common
reasons that CMOS data is lost include the following:
The on-board battery has run out.
Cards have been removed or inserted in a way that releases electrostatic
discharge (ESD).
Improper handling of the motherboard has caused electrical short circuits
or failure due to ESD.
Something has been dropped on the motherboard.
There is dirt on the motherboard.
The power supply is faulty.
There have been electrical surges.
The following types of errors indicate lost or corrupt CMOS data:
CMOS configuration mismatch
CMOS date/time not set
No boot device available
CMOS battery state low
Cannot locate hard disk drive or floppy disk drive
It is wise to back up the CMOS setup just as you back up important data. One
way to do this is to write down the information (especially before making
hardware changes). There are many third-party CMOS save-and-restore utility
programs available.
NOTE
Many newer machines that run versions of Windows 95 and later
and that offer Plug and Play place less emphasis on the CMOS. The
BIOS information is stored with the device and is automatically
detected at boot.
The CMOS Battery
The CMOS chip requires a small trickle voltage from a battery to keep its
memory alive. When the battery gets low or dies, the computer will experience
a sudden memory loss and thus lose settings. It might not be able to find the
floppy disk or first hard disk drive and therefore display an error indicating
that it cannot find the system or nonsystem disk.
The voltage of CMOS batteries ranges from 3 to 6 volts. Check the
motherboard or the motherboard documentation to determine the actual
battery requirements. Batteries come as either on-board (NiCad batteries,
soldered in place or in a fixture, that last from five to seven years) or external
(nonrechargeable AA alkaline batteries that last from two to four years). The
3-volt lithium watch battery is becoming very popular with motherboard
suppliers. Many of these are mounted in a special holder so that the battery
can be easily changed; however, some manufacturers solder them in place.
The first clue that the battery is weakening is that the CMOS clock begins to
slow down. Exit to DOS and, when you see the C prompt (C:), type time. If
you notice the clock is slow, it's probably time to change the battery.
NOTE
Remember that an MS-DOS machine (as well as those running
Windows 95 and later) uses the CMOS clock to get the date and
time at startup. After the computer is running, MS-DOS uses the
memory refresh timer on the memory controller to keep time. This
works well, but because the refresh timer is not very accurate
about seconds, you will lose one or two seconds per day. If you
never turn off a computer, it could lose time. Do not confuse this
with a bad battery. When you reboot, the computer will update
itself to the correct time from the CMOS. If the CMOS battery is
low, it will still show the incorrect time.
When the CMOS battery dies completely, you will get lost CMOS errors, as
previously described. If you reload the CMOS data and the errors return, it's
time to change the battery. Although the computer will hold CMOS information
during the week, sometimes, over the weekend—when the computer is turned
off for two days—the CMOS data will be lost. Do not let these seemingly
"intermittent" problems fool you. Sometimes, before a battery dies, but after it
has started to fail, it will still be able to hold CMOS settings for a short time
after the computer is off. Any time a computer loses the CMOS information
more than once in a week, it's a sure sign that you need to replace the battery
immediately—if only to eliminate the battery as the source of the problem.
After replacing the battery, you must run the setup utility and restore any
CMOS settings.
NOTE
The CMOS chip contains a capacitor that allows replacement of the
battery without losing data. For motherboards with soldered onboard batteries, there is usually a connection that allows you to
add an external battery to replace a worn-out internal one. Be
sure that the external battery has the same voltage as the onboard battery you are replacing. Some older PCs use a battery
pack with four AA cells or a single 9-volt battery. These should be
replaced with a special PC battery pack to provide longer life.
The best source of information about replacing a CMOS battery is the
documentation that comes with the motherboard.
Today's computers are becoming less reliant on battery backup for CMOS. With
Windows Plug and Play technology, devices come with their own BIOS, which
the system reads each time the computer is booted. This does not eliminate
the need for CMOS or batteries, but it minimizes the impact of a battery
failure. At the very least, you will still need to retain the date and time
information.
All Other Chips
It would be impossible to put all the necessary BIOS information for every
conceivable piece of hardware on one chip. It would also be impractical, as new
devices are released almost monthly. Upgrading a machine would require a
new BIOS chip (or a new version of the flash BIOS) every time. Fortunately,
there are other ways to handle this challenge.
ROM Chips with BIOS
BIOS can be put on the hardware device itself. Many new add-on boards, such
as display adapters, network interface cards, and sound cards, have their own
on-board ROM chip. Because the system BIOS doesn't have a clue about how
to communicate with the new device, this card includes its own BIOS.
Loading Device Drivers
Using device drivers is the most popular way to provide BIOS support for
hardware. A device driver is a program that acts as an interface between the
operating system and the control circuits that operate the device. For example,
Windows has "generic" code that opens a file, but the driver for the disk drive
takes care of low-level tasks like positioning the read head, reading or writing
blocks of data, and so on. Thus, applications programmers don't usually have
to worry about these details and can assume that any hardware supported by
a device driver will work.
Just how a device driver is invoked depends on the operating system, the
hardware, and the software design. Although few devices still use the
CONFIG.SYS file to load drivers, it provides an easy way to see how they work.
Every time the computer is booted up, the CONFIG.SYS file is read and the
device drivers are loaded from the hard disk drive into RAM.
Some examples of device drivers in CONFIG.SYS are:
DEVICE=C:\DOS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE NOEMS
DEVICEHIGH =C:\SCSI\ASPIPP3.SYS /D /Z
DEVICEHIGH =C:\DOS\DRVSPACE.SYS
DEVICEHIGH =C:\CDROM\MTMCDAI.SYS /L=001
Loading device drivers in CONFIG.SYS is a requirement for machines running
MS-DOS. The Windows 95, Windows 98, Windows Me, and Windows 2000
operating systems have their own drivers that are loaded as part of startup.
(Drivers are covered in more detail in the appropriate operating system
chapters later in this book.) Occasionally, drivers become outdated or have
problems. You can obtain new drivers directly from the device manufacturers
(often directly from their Web sites).
NOTE
Even hardware that installs without a setup disk can be changing
the registry if it is a Plug and Play device that is recognized by the
operating system. Erratic problems can occur if a device is
improperly identified. Under Windows 95, Windows 98, Windows
Me, or Windows 2000, check the System section of the Control
Panel to identify possible conflicts.
Power-On Self Test
Every time a PC is turned on or reset using the Reset button or Windows
Restart command, the computer is rebooted and reset to its basic operating
condition. The system BIOS program starts by invoking a special program
(stored on a ROM chip) called the power-on self test (POST). The POST sends
out standardized commands that check every primary device (in more
technical terms, it runs an internal self-diagnostic routine).
The POST has two stages:
Test 1 occurs before and during the test of the video.
Test 2 occurs after the video has been tested.
This division determines whether the computer will display errors by beeping
or showing them on the screen. The POST does not assume the video works
until it has been tested. The POST does assume that the speaker always
works, but to let you know that the speaker is working, all computers beep on
startup. Depending on the BIOS type, the POST might also sound a single beep
when it's done to let you know the boot process was successful. If something
goes wrong, the POST sends a series of beep codes to let you know what the
problem is or where to start looking for it.
Beep Codes Before and During the Video Test
The purpose of the first POST test is to check the most basic components. The
exact order, number of tests, and error states will vary from product to
product. In a healthy system, the POST reports by using a series of beep codes
and screen messages to convey that all components are working. Then it
transfers control to the boot drive, which loads the operating system. The
POST is a good indication that the hardware is in working order.
If a problem occurs, the POST routine attempts to report the problem. This is
also done using beep codes and (if possible) screen prompts. Some error codes
are specific to chip sets or custom products, and the exact message and
meaning can vary from system to system. (See the POST code references in
the system manual that shipped with the PC or the motherboard to obtain
references for detailed error messages and beeps.) The following table lists the
basic beep codes for AMI and Phoenix BIOSs.
Number of
Possible Problem
Beeps
1
DRAM refresh failure
2
Parity circuit failure
3
Base 64 KB or CMOS RAM failure
4
System timer
5
Processor failure
6
Keyboard controller or Gate A20 error
7
Virtual mode exception error
8
Display monitor write/read test failure
9
ROM BIOS checksum error
10
CMOS RAM shutdown register failure
1 long, 3 short
Conventional/extended memory test failure
1 long, 8 short
Display test and display vertical and horizontal retrace
test failure
Troubleshooting After a Beep
After a beep code has been recognized, there are a few things you can do to
troubleshoot the error. The following table suggests some solutions. Keep in
mind that, in many cases, it can be less expensive to replace the motherboard
than to replace a chip.
Problem
Solution
RAM refresh
failure
Reseat and clean the RAM chips.
Parity error
RAM bit error
Base 64-KB
error
Replace individual memory chips until the problem is
corrected.
8042 error
Reseat and clean keyboard chip.
(keyboard chip)
Gate A20 error
Check operating system. Replace keyboard. Replace
motherboard.
BIOS checksum Reseat ROM chip. Replace BIOS chip.
error
Video errors
Reseat video card. Replace video card.
Cache memory
error
Reseat and clean cache chips. Verify cache jumper
settings are correct. Replace cache chips.
Any other
problems
Reseat expansion cards. Clean motherboard. Replace
motherboard.
NOTE
Many computers will generate beep codes when the only problem
is a bad power supply! Turn the computer off and on three or four
times to see if the same beep code is generated every time. If so,
it's probably a legitimate beep code that concerns the hardware
and not the power supply.
Since early 1996, some BIOS programs have eliminated many
beep codes. However, identifying beep codes can still be part of
the A+ Certification exam.
Error Messages—After the Video Test
After successfully testing the video, the POST will display any error messages
on the screen. These errors are displayed in one of two ways: numeric error
codes or text error messages.
Numeric Error Codes
When a computer generates a numeric error code, the machine locks up and
the error code appears in the upper-left corner of the screen. The following
table lists some common numeric error codes, but it is a good idea to check
the manual before beginning repairs based on a beep code or error message.
Error Code
Problem
301
The keyboard is broken or not plugged in.
1701
The hard disk drive controller is bad.
7301
The floppy disk drive controller is bad.
161
The battery is dead.
1101
The serial card is bad.
Text Error Codes
BIOS manufacturers have stopped using numeric error codes and have
replaced them with about 30 text messages. Instead of numbers, you get text
that is usually, but not always, self-explanatory.
How Bad Is It?
There are two levels of error codes during POST: fatal and nonfatal. As the
name implies, fatal errors will halt the system without attempting to load the
operating system. Memory problems or a faulty disk or display adapter are
examples of fatal errors. Nonfatal errors like a "missing" floppy disk drive will
still result in the system attempting to load the operating system (and often
succeeding).
In most cases, the POST procedure does a good job of testing components. If it
gives a clean bill of health to the hardware, failure to boot will often lie in the
operating system. You can use a bootable floppy disk in most cases to access
the hard disk drive, or boot Windows using the Safe Start approach (press the
F8 key just after the POST completes) and check for conflicting settings.
POST Cards
More difficult to resolve is a hardware problem that keeps the POST from
issuing any report at all. When you face this type of situation, you will find
that this is where a POST card earns its keep. These special diagnostic
expansion cards monitor the POST process and display all codes (usually in
two-digit hexadecimal format) as the system runs the POST. The technician
can then decode this information using the manufacturer's manual. More
advanced models can also run advanced series of tests to isolate erratic
problems.
When choosing a POST card, be sure that it will work with the types of
machines you plan to test. Most are based on the Industry Standard
Architecture (ISA) slot and work with most Intel CPUs. That means they should
help with AT (80286 processors) and later-based PCs that use x86 processors.
Basic models give only POST codes. More advanced models also can check
direct memory access (DMA), IRQ (interrupt request), and port functions.
Some come with fancy diagnostic software. The more features, the higher the
price tag. However, a POST card will save a lot of time and frustration, making
it a worthwhile addition to any PC toolkit.
Lesson Summary
The following points summarize the main elements of this lesson:
Understanding ROM BIOS is key to keeping a computer up and running.
CMOS setup defines the data a computer needs to communicate with its
hardware (such as its drives).
The CMOS battery maintains BIOS data when computer power is turned
off.
A POST card can quickly pay for itself by helping to isolate problems when
the POST routine fails to provide a report.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Computer Cases
The functions of the case are to house the computer's internal
components, connect the computer to the outside world via ports and
connectors, and protect the computer from damage.
To prevent EMI, avoid running a computer without the cover on.
Motherboards
The motherboard components define the capabilities of a computer.
Not all motherboards are the same. Some manufacturers have
proprietary motherboards that can be used only in their own computers.
They will also require proprietary parts for expansion. Generally, these
motherboards are of higher quality (and price).
ROM BIOS
BIOS chips are used to provide data to the CPU; this data tells the CPU
how to operate specific devices.
CMOS is a BIOS chip that can have its data updated. The CMOS setup
program is used to make changes.
CMOS chips require a battery to save the data when power to the
computer is off.
Some of the newer BIOS chips are updatable. These are called flash
BIOS.
A device driver is a program that acts as an interface between the
operating system and the control circuits that operate the device.
On machines running MS-DOS, device drivers are loaded by the
CONFIG.SYS file.
Computers running Windows 95, Windows 98, Windows Me, or Windows
2000 load their own device drivers and do not require a CONFIG.SYS file.
POST is used to check a computer before it boots.
POST errors are indicated by beeps before the video is checked, and by
text after the video check.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. What is the main function of the motherboard?
2. Name the typical chips found in a chip set.
3. What is EMI?
4. What are ROM chips used for?
5. Name the three types of ROM chips.
6. Describe what makes the CMOS special.
7. How can a technician use the POST beep codes?
8. What is a device driver?
9. What information is contained in the CMOS?
10. Define the POST and describe its function.
Answers
3 4
Chapter 7
Memory
About This Chapter
In earlier chapters, we learned that the CPU (central processing unit) and
motherboard (bus and controllers) are critical components that help determine
the overall speed with which a computer can process data. This chapter looks
at another important system component and performance factor: memory.
Technicians are often asked to upgrade PCs by adding more memory, and
memory conflicts or errors commonly prompt calls for assistance by users.
Understanding how memory works, how to choose the right memory for a
given system, and how to troubleshoot memory problems is critical to being
successful as a computer technician.
Before You Begin
A clear understanding of microprocessors, motherboards, and computer buses,
covered in earlier chapters, is required before beginning this chapter.
3 4
Lesson 1: ROM and RAM
As a computer technician, you will encounter various types of memory. This
lesson defines the different types of memory, shows you how to locate memory
in a computer, and discusses how to expand or add new memory.
After this lesson, you will be able to
Identify basic concepts related to computer memory
Define the types of memory and describe their advantages and
disadvantages
Explain memory upgrade options and issues
Estimated lesson time: 45 minutes
Defining Memory
A host of terms and acronyms relate to the memory technology used in
personal computers. A technician must understand the key concepts involved.
You must be able to identify the distinctions among the major memory
components and to distinguish between memory and storage.
All computer memory is used to hold binary strings of data to be manipulated
by the CPU. Think of memory as a vast bank of switches with two positions: on
or off. Off is given the value of 0; on is given the value of 1. This allows the
switches to hold binary data based on whether they are open or closed. By
stringing a series of switches together, larger numbers and code values can be
represented.
Nonvolatile and Volatile Memory
There are two major classes of computer memory: nonvolatile and volatile.
Nonvolatile memory is retained even if the power to the computer is shut off.
The setup data held in CMOS (complementary metal-oxide semiconductor),
discussed in the preceding lessons, is a good example of nonvolatile memory.
If the data is lost when the computer loses power, the memory is said to be
volatile.
Active memory is a state in which a block of code or data is directly accessible
to the CPU for reference or manipulation. When data is located outside the
system's active memory, it is said to be in storage. Storage devices include
floppy disk and hard disk drives, optical media, and tape units.
Active memory is faster than storage because the information is already on
the system, there are fewer physical (and no mechanical) operations involved
in obtaining the data, and the CPU has direct control over the memory.
ROM
ROM (read-only memory) is nonvolatile memory, generally installed by the
vendor of the computer during the process of manufacturing the motherboard
or secondary components that need to retain code when the machine is turned
off. With the use of ROM, information that is required to start and run the
computer cannot be lost or changed.
ROM is used extensively to program operation of computers, as well as in
devices like cameras and controls for the fuel injectors in modern cars.
However, ROM plays a limited role in the PC (personal computer). Here, it
holds the instructions for performing the power-on self test (POST) routine and
the BIOS (basic input/output system) information used to describe the system
configuration. For more detailed information, refer to Chapter 6, "Motherboard
and ROM BIOS."
In most cases, a technician will be concerned with ROM only if it has failed and
requires replacement, needs to be upgraded, or conflicts with other memory
installed in the system. A repairperson or technician does not usually directly
control the actual code in ROM.
RAM
RAM (random access memory) is what is most often referred to when PC
memory is discussed. RAM is the form of volatile memory used to hold
temporary instructions and data for manipulation while the system is running.
The term random is applied because the CPU can access or place data to and
from any addressable RAM on the system. If power to the system is lost, all
RAM is lost as well.
Usually, when referring to RAM, we are speaking of some variation of DRAM
(dynamic RAM) or the newer SDRAM (synchronous DRAM). These are the most
common forms of RAM used in the modern PC.
DRAM works by using a microscopic capacitor and a microscopic transistor to
store each data bit. A charged capacitor represents a value of 1, and a
discharged capacitor represents a value of 0. A capacitor works like a battery—
it holds a charge and then releases it. Unlike a battery, which holds a charge
for months, the tiny capacitors in DRAM hold their charges for only fractions of
a second. Therefore, DRAM needs an entire set of circuitry just to keep the
capacitors charged. The process of recharging these capacitors is called
refreshing. Without refreshing, the data would be lost. This is another reason
DRAM is called volatile memory.
All PC CPUs handle data in 8-bit blocks. Each block, known as a byte, denotes
how many bits the CPU can move in and out of memory at one time. The
number is an indication of how rapidly data can be manipulated and arranged
in system memory. Don't confuse this byte with the amount of system
memory, which is usually expressed in megabytes (MB). System memory is
the total amount of active memory that is available to the CPU as a temporary
work area.
Each transaction between the CPU and memory is called a bus cycle. The
amount of memory that a CPU can address in a single bus cycle has a major
effect on overall system performance and determines the design of memory
that the system can use. The width of the system's memory bus must match
the number of data bits per cycle of the CPU.
All computers have some form of memory controller, which handles the
movement of data to and from the CPU and the system memory banks. The
memory controller is also responsible for the integrity of the data as it is
swapped in and out. There are two primary methods of ensuring that the data
received is the same as the data sent: parity and error-correction coding
(ECC).
Parity
Parity is a method of ensuring data integrity that adds an extra bit (the parity
bit) along with each 8-bit bus cycle. There are two kinds of parity: even and
odd. Both use a three-step process to validate a bus transaction; however,
they do it in opposite ways.
In Step 1, both methods set the value of the parity bit based on the even
or odd number that represents the sum of the data bits as the first step.
In Step 2, the string goes into DRAM.
In Step 3, the parity circuit checks the math. If the parity bit matches the
parity bit of the number that represents the sum of the binary string sent,
the data is passed on. If it fails the test, an error is reported. Just how
that error is handled and reported to the user varies with each operating
system.
ECC
A more robust technology, ECC can detect errors beyond the limits of the
simpler parity method. It adds extra information about the bits, which is then
evaluated to determine if there are problems with individual bits in the data
string.
Access Speed
Access speed, denoted in nanoseconds (ns), is the amount of time it takes for
the RAM to provide requested data to the memory controller. Here, smaller is
better. Be sure to buy RAM that is at least as fast as that listed as standard for
the computer in question.
A typical total response time for a 70-ns DRAM chip is between 90 and 120 ns.
This includes the time required to access the address bus and data bus. Most
486- and Pentium-based machines use either 70-ns or 60-ns DRAM chips,
although 50-ns chips are now available. The access speed of a chip is usually
printed on the chip (often as part of the identification number).
Here are a few important things to remember about access speed when adding
memory:
Any add-on memory should be the same speed as or faster (lower
number) than any existing memory.
You cannot mix memory modules with different speeds in the same bank
(a bank is a set of several memory modules).
You should check the motherboard specifications for the recommended
memory chip speed.
RAM Packaging
Over the years, the way memory has been packaged and placed on the
motherboard has changed several times. As faster processors developed and
system requirements for applications increased, so did the need for more and
faster memory. The new memory designs often required new packaging and
connection technology. That trend will continue, and technicians must stay
current on the different memory types and their appropriate applications.
Early versions of RAM were installed as single chips, usually 1-bit-wide DIP
(dual inline package), as shown in Figure 7.1. In some cases, this was soldered
right onto the motherboard, but most often it was seated in a socket, offering
a simpler method of removal and replacement. Some older machines have
special memory expansion cards that contain several rows of sockets. These
cards are placed in a slot on the motherboard.
To upgrade or add memory, new chips had to be individually installed on the
motherboard (eight or nine chips per row—nine chips if using parity). This
could be challenging, because each chip had 16 wires that needed to be
perfectly aligned before insertion into the base. The notch in one end denoted
the side that had pin 1.
Figure 7.1 A DIP DRAM chip
As the amount of memory and the need for speed increased, manufacturers
started to market modules containing several chips that allowed for easier
installation and larger capacity. These modules come in a variety of physical
configurations. Technicians must be able to identify both the type and amount
of memory a computer requires for optimum performance.
TIP
Identifying the amount of memory actually working on a PC is
easy if the PC is operational: Simply boot the system and view the
memory values given during the POST. In some cases, this is also
a useful way to determine if a memory block is improperly
installed. If that is the case, the computer might fail to boot or the
POST might report a lower figure than the actual amount of RAM
present.
SIPPs
One of the first module forms of DRAM, the SIPP (single inline pinned package)
is a printed circuit board with individual DRAM chips mounted on it, as shown
in Figure 7.2. Physically, a SIPP module looks like a rectangular card with a
single row of pins along one edge. The SIPP had a very short time in the sun
due to the fragile nature of these pins.
Figure 7.2 SIPP
CAUTION
You won't likely see any SIPPs, but if you do, take special care
when replacing them in the motherboard. SIPPs have a row of pins
along one side. These pins are easily broken, and care should be
taken to avoid damaging them during installation.
SIMMs (30-Pin)
SIMMs (single inline memory modules) quickly replaced SIPPs because they
are easier to install. They are similar to SIPPs with one exception—they
require no pins; 30-pin SIMMs have 30 contacts in a single row along the
lower edge (see Figure 7.3). A 30-pin SIMM can have as few as two or as
many as nine individual DRAM chips. Although SIMM modules can have pin
counts as high as 200, in PCs, 30- and 72-pin versions are the most common.
Figure 7.3 30-pin SIMM
CAUTION
Avoid touching the contacts on SIMMs, and use proper handling to
reduce the risk of damage from electrostatic discharge (ESD).
Memory Configuration
The capability of the computer's CPU, its memory configuration, and its
operating system all play roles in how the computer's memory is allocated.
Technicians should understand the terms and processes involved, both for
their own benefit and to explain the details to a customer if the question
arises.
The power of a processor is often expressed by how many such pieces it can
handle at a time. For example, the original Intel Pentium is a 64-bit CPU,
meaning that it can handle 64 bits at once. That amounts to 8 bytes (8 × 8).
These terms always refer to byte-wide memory (8 bits).
When the bus cycle demand is greater than the number of bits a memory
module provides, more modules must be added to be able to meet the
demand. The most common approach is to employ a bank of modules, matched
to the bit width equal to the data demands of the CPU, and the entire data
bus. When most new CPUs are introduced, the width of the design is the same
as the old memory types, and modules must be used in banks until a new
memory design is available. For example, an 8-bit data bus (8086 or 8088)
needs 8-bit-wide memory to fill one bank. A 16-bit data bus requires 16-bitwide memory to fill one bank, and so on. If you install 30-pin SIMMs (each is 8
bits wide) on a 16-bit machine, you will need two rows of chips to completely
fill the data bus.
NOTE
Each of the rows that make a bank must be filled with identical
chips (size and speed). See Figure 7.4.
Figure 7.4 Banking
Most motherboards provide several rows of slots for adding memory, often
referred to as banks. Be careful with the word bank. It is used to describe the
necessary rows of chips, as well as the slots into which they are inserted.
SIMMs usually require matched pairs to form a bank of memory, whereas
DIMMS (dual inline memory modules) require only one card (we will examine
different types of modules later in this chapter). To calculate the number of
SIMMs needed to make one bank, use the following formula: Divide the
number of data bits per CPU cycle by the bit width of the module. (For 30-pin
SIMMs, that is always 8 bits.) A 32-bit external data bus with 30-pin SIMMs
requires 32 (the width of the data bus) divided by 8 (the number of bits per
SIMM module), or 4 modules per bank.
There are some rules to follow when banking:
All rows in a bank must be either completely filled or completely empty.
Each bank is numbered, starting with bank 0.
In most systems, DRAM should be installed in bank 0 before any other
bank is used.
Refer to the motherboard documentation for bank numbering and
installation directions.
Specifying SIPPs and SIMMs
When speaking of DRAM SIPPs and SIMMs, we use two values to determine
how much memory a unit can hold:
Width. 1 bit, 4 bits (a nibble), 8 bits (a byte), or 16 bits (a word), and so
on.
Depth. How deep the chip is: 256 KB, 1 MB, 4 MB, 8 MB, 16 MB, 32 MB,
and so on.
You can determine the size of the DRAM chip by combining the depth and
width of the chip.
Here are a few points to remember when specifying DRAM:
When upgrading memory, you add megabytes.
When purchasing DRAM, you buy bits, usually in the form of MB.
Calculate chip size by multiplying depth by width; the result is measured
in bits.
One KB of memory is equal to 8192 bits (1024 × 8).
One MB is equal to 8,388,608 bits (1024 × 1024 × 8).
The following table lists common DRAM module sizes.
Chip (Depth ×
Width)
Number of Chips per
Module
Memory per
Module
1 MB × 1
8
1 MB
1 MB × 4
2
1 MB
1 MB × 16
1
2 MB
2 MB × 8
1
2 MB
4 MB × 1
8
4 MB
4 MB × 4
2
4 MB
The 72-Pin SIMM
With the advent of 32- and 64-bit CPUs, the bank began to take up too much
space on the motherboard and added to the cost of memory. (The board that
houses the chips often costs more than the DRAM chips.) Enter 72-pin SIMMs,
with 72 pins on each card. One of these is four times wider than a 30-pin
SIMM, which is 8 bits wide (see Figures 7.5 and 7.6). Therefore, a
motherboard requiring four rows of 30-pin SIMMs to fill one bank needs only
one 72-pin SIMM. Virtually all Pentium and Pentium Pro systems use 72-pin
SIMMs.
Because 72-pin SIMMs are 32 bits wide, the term x 32 is used to describe
them. A 1 MB × 32 SIMM contains 4 MB of RAM because it is 4 bytes wide (1
MB of RAM is 1,048,576 × 32, which equals 4 MB). Remember, memory is
measured in bytes, and chips are measured in bits.
Figure 7.5 A 72-pin SIMM
There are many varieties of SIMMs on the market. The following table lists
some common 72-pin SIMMs.
Configuration
Memory
4 MB × 36
16 MB, parity
8 MB × 32
32 MB, no parity
8 MB × 36
32 MB, parity
16 MB × 32
64 MB, no parity
16 MB × 36
64 MB, parity
Voltage
All early PCs used 5-volt circuits to power components, including memory.
Today, the trend is to use 3.3-volt power unless 5 volts are required for a
specific part of the system (such as a hard disk drive). Be sure to check the
voltage of the memory before installing a module.
Installing SIMMs
When installing SIMMs:
Always use precautions to avoid ESD. Refer to Chapter 22, "The Basics of
Electrical Energy," for details.
Always handle SIMMs carefully—keep your fingers on the plastic edges.
There is little worse than destroying a 16-MB SIMM because of static
discharge.
All SIMMs have a notch on one side that prevents them from being
installed improperly. If you cannot insert the SIMM easily, it's probably
backward.
SIMMs are inserted into the slot at a 45-degree angle along the wide side
(see Figure 7.6).
After the SIMM is securely seated in the slot, push it upright until the
holding clamps on either side are secured.
IMPORTANT
SIMMs are extremely sensitive to static. Be sure to handle them
carefully.
Figure 7.6 Installing SIMMs
After the chip is physically installed:
Turn on the computer. If the DRAM is installed correctly, the RAM count
on the computer will reflect the new value.
If the RAM value has not changed, it is likely that either a bank is
disabled or the SIMMs are installed incorrectly. Check the motherboard
documentation to determine if a jumper needs to be changed to turn on
the SIMM.
If the computer does not boot and the screen is blank, the RAM was not
installed correctly.
NOTE
When a computer is booting, the RAM count is based on units of
1024 bytes. One MB of RAM should show as 1024, 2 MB as 2048,
4 MB as 4096, and so on. Most RAM counts appear to stop before
they get to the value expected (less than 1 MB). In reality, the
computer is finished and moving on to the next task so fast that
the result does not display on the screen. If the POST reports the
full number, the memory is all there. If the POST does not report
the full number, you should make sure that all modules are
properly seated, of the right type, and working.
After the RAM is installed, and the RAM count correctly reflects the new
value, the CMOS needs to be updated. On most machines, this is done
automatically and no intervention is required.
If you get an error similar to "CMOS Memory Mismatch—Press Fl to continue,"
access the CMOS with the CMOS setup program, then save and exit (changes
will be automatically recorded). The CMOS will be reset.
If the system fails to boot or reports less than the amount of memory actually
installed, recheck the modules to make sure they are seated properly
according to the motherboard manual and that the right type and amount are
present.
Dual Inline Memory Modules
These newer modules look much like SIMMs, but come in a package with 168
pins and have a different wiring structure, so that one card can form a
complete bank. These are the memory packages used on virtually all new
motherboards.
DIMMS are a real improvement over older memory modules. They provide
larger amounts of RAM on a single module and are easy to install. They slide
straight down into a slot and are secured by a pair of locks that swing into
place above the card as it seats fully in the slot. Check the motherboard
manual or the vendor's Web site for the approved list of DIMM modules. There
are many variations in electronic design (parity, non-parity, etc.), and you
must make sure that the DIMM will actually work with the combination of
motherboard and CPU you are working on. Just because the card fits does not
mean it will work.
Cache Memory
To cache is to set something aside, or to store for anticipated use. Early
explorers would arrange to have a cache of food or other supplies positioned
along their route of travel. This made their travel easier since they didn't have
to carry anything other than essentials needed for each portion of the trip. The
same concept can be applied to CPU operations and computer system design.
Caching, in PC terms, is the holding of a recently or frequently used code or
data in a special memory location for rapid retrieval. Speed is everything when
it comes to computers. Mass storage is much slower than RAM, and RAM is
much slower than the CPU. The high-speed memory chip generally used for
caching is called static RAM (SRAM).
SRAM
SRAM does not use capacitors to store 1s and 0s. Instead, SRAM uses a special
circuit called a flip-flop. The advantages of SRAM are that it is fast and it does
not have to be refreshed because it uses the flip-flop circuit to store each bit.
A flip-flop circuit will toggle on or off and retain its position, whereas a
standard memory circuit requires constant refreshing to maintain an on state.
The main disadvantage of SRAM is that it is more expensive than DRAM.
Caching: The Layered Look
Caching is a very common technology in PC operations and can be found on
individual computers, peripheral devices like graphics cards, and on and
around the CPU. While working, the CPU is constantly requesting and using
information and executing code. The closer the necessary data is to the CPU,
the faster the system can locate it and execute the operation. Of course, it
would be impossible to keep all necessary information in active memory; cost
and logistics make it necessary to prioritize how large the cache is on a
system, and how it is organized.
Caches are organized into layers. The highest layer is closest to the device
(such as the CPU) using it. On early PCs, caches were usually separate chips.
Today, it is not uncommon to have two levels of cache built right into the CPU,
but a cache is not limited to dynamic memory. Mass storage devices like hard
drives can also be used to store less commonly used code or data.
Internal Cache (L1)
Starting with the 486 chips, a cache has been included on every CPU. This
original on-board cache is known as the L1 (level 1) or internal cache. All
commands for the processor go through the cache. The cache stores a backlog
of commands so that if a wait state is encountered, the CPU can continue to
process using commands from the cache. Caching will store any code that has
been read and keep it available for the CPU to use. This eliminates the need to
wait for fetching of the data from DRAM.
External Cache (L2)
Additional cache can be added to most computers, depending on the
motherboard. This cache is mounted directly on the motherboard, outside the
CPU. The external cache is also called L2 (level 2) and is the same as L1, but
larger. L2 can also (on some motherboards) be added or expanded. When
installing any L2 cache, be sure to check the CMOS setup and enable the
cache. Some computer systems are now also employing a Level 3 cache.
Write-Back vs. Write-Through
As mentioned, the primary use of a cache is to increase the speed of data from
RAM to the CPU. Some caches immediately send all data directly to RAM, even
if it means hitting a wait state. This is called write-through cache, shown in
Figure 7.7.
Figure 7.7 Write-through cache
Some caches store the data for a time and send it to RAM later. This is called
write-back cache, shown in Figure 7.8.
Write-back caches are harder to implement but are much more powerful than
write-through caches, because the CPU does not have to stop for the wait state
of the RAM. However, write-through caches are less expensive.
Figure 7.8 Write-back cache
Lesson Summary
The following points summarize the main elements of this lesson:
There are two basic kinds of memory in a computer: ROM and RAM.
Memory chips come in many sizes and shapes: DIPPs, SIPPs, DRAM,
SRAM.
Installing memory (RAM) is easy; however, you must be able to match
the size and configuration of the memory chips to the motherboard.
The number of memory modules needed to fill one memory bank equals
the width of the external data bus (in bits) divided by the width of the
SIMM (in bits).
Cache memory is used to increase the performance of a computer.
Cache memory (SRAM) is faster, but more expensive, than the standard
DRAM; therefore, it is used in small quantities and for special purposes.
There are two types of cache memory: L1 and L2.
3 4
Lesson 2: Memory Mapping
Computer memory has many functions. Some memory is reserved for
particular uses by the processor and, if improperly allocated, will cause
problems. Understanding how to identify and manage memory is key to
optimizing a computer. In this lesson, you learn how memory is allocated.
After this lesson, you will be able to
Use hexadecimal numbers
Define the different types of memory access
Optimize memory allocation
Estimated lesson time: 20 minutes
The Workings of Hexadecimal Code
Chapter 2, "Understanding Electronic Communication," introduced the concept
of binary notation. This is how computers count—by setting the value of a twoposition switch to either 0 (off) or 1 (on). Ones and zeroes work well when
machines are conversing, but that language can be somewhat confusing for
computer designers and programmers. To simplify the representation of
numbers and notations, designers and programmers use a numbering system
called hexadecimal notation (also known simply as hex). This is a numbering
system based on 16 instead of 10. Fortunately, computer technicians do not
have to be experts in hexadecimal notation. You do, however, need to know
how to use the numbering system as it relates to computer memory.
Hexadecimal notation is used to simplify notation of binary code in much the
same way that we sometimes count in fives or tens when it is more convenient
than working our way through a problem by ones. You might ask how anyone
would find it simpler to count in hex. Well, in dealing with a system that uses
8 bits, addressing counting locations in hex (a system based on eight
positions) makes perfect sense.
All address buses and wires within a computer come in some multiple of 4 (8,
16, 20, 24, 32). Because there are 16 different combinations, the 16 unique
characters of the base-16 numbering system are a natural choice for computer
shorthand when referring to memory locations or a bus address. The following
table contrasts binary notation with hex shorthand.
Binary Number
Hex Shorthand
Binary Number
Hex Shorthand
0000
0
1010
A
0001
1
1011
B
0010
2
1100
C
0011
3
1101
D
0100
4
1110
E
0101
5
1111
F
0110
6
0111
7
1000
8
1001
9
Hexadecimal Shorthand
There is no need to say:
10110110011000101101
To use hex shorthand:
Break the 20 digits into 5 sets:
1011
0110
0110
0010
1101
Give each 4-character set its hex shorthand:
1011
0110
0110
B
6
6
Hex shorthand = B662D
0010
2
1101
D
To represent all the possible addresses for the 20-bit address bus, we use 5
hex values (0 to F) that map to their binary equivalents, from all 0s:
0000
0
0000
0
0000
0
0000
0
0000
0
1111
F
1111
F
1111
F
1111
F
to all 1s:
1111
F
Each of the possible memory locations for the Intel 8088 can be represented
by 5-digit hexadecimal values, starting at 00000 and ending at FFFFF.
Memory Allocation
Previously in this chapter, we discussed memory in terms of the chips
themselves. In this section, we look at how that memory is allocated for use by
the CPU. This is called memory mapping and it uses hexadecimal addresses to
define ranges of memory.
The original processors developed by Intel were unable to use more than 1 MB
of RAM, and the original IBM PC allowed only the first 640 KB of memory for
direct use. MS-DOS applications were written to conform to this limitation. As
application requirements grew, programmers needed to optimize the use of
memory to make the most of the available space. This 1 MB of memory was
divided into two sections. The first 640 KB was reserved for the operating
system and applications (designated as conventional memory). The remaining
384 KB of RAM (designated as upper memory) was earmarked for running the
computer's own housekeeping needs (BIOS, video RAM, ROM, and so on).
Although some early PC clones had firmware that could make direct use of the
upper memory block available to programmers, actually doing so would result
in hardware and software incompatibility issues (see Figure 7.9).
Figure 7.9 IBM PC/MS-DOS memory map
Under MS-DOS and Microsoft Windows 3.x, the 640-KB area needed to be kept
as free as possible for program use. MS-DOS memory optimization ensures
that MS-DOS applications have as much of this memory as possible. The MSDOS limitations no longer apply to Windows versions operating in 32-bit mode
(Microsoft Windows 95 and later) and most newer operating systems.
However, the old memory problems still are a factor when running MS-DOS,
Windows 3.x-based programs on older machines, or MS-DOS compatibility
mode with the more advanced operating systems. While you may never run
into this problem, you should be aware of it as it can cause very erratic—and
often severe—problems.
Types of Memory Access
When we speak of memory in a computer, we are generally speaking of RAM,
because ROM cannot be written to by either the system or applications.
Although we have only one single supply of RAM, under MS-DOS-based
operating systems, it is usually segmented into smaller blocks for actual use.
Extended Memory Specification (XMS)
RAM above the 1-MB address is called extended memory. With the
introduction of the 80286 processor, memory was addressable up to 16 MB.
Starting with the 80386DX processor, memory was addressable up to 4 GB.
Extended memory is accessed through an extended memory manager
(HIMEM.SYS).
Conventional Memory
Conventional memory is the amount of RAM, typically 640 KB, addressable by
an IBM PC or compatible machine operating in real mode. (Real mode is the
only operating mode supported by MS-DOS.) Conventional memory is located
in the area between 0 and 640 KB. Without the use of special techniques,
conventional memory is the only kind of RAM accessible in DOS mode and DOS
mode programs.
MS-DOS Protected Mode Interface
MS-DOS Protected Mode Interface (DPMI) is a specification that allows multiple
applications to access extended memory at the same time. Most memorymanager producers and applications developers have endorsed this
specification, and Windows uses the DPMI specification.
Expanded Memory Specification
EMS (Expanded Memory Specification), developed by Lotus/Intel/Microsoft,
uses a 64-KB section of memory (usually in upper memory) to provide a
"window" in which data can be written. Once in this area, the data can be
transferred to the expanded memory. The memory chips are located on an
expansion card installed inside the computer. The data is paged or swapped to
and from the CPU through this window (see Figure 7.10).
Figure 7.10 Expanded memory
Expanded memory can provide up to 32 MB of additional memory, and because
it is loaded from a 64-KB section, it is below the 1-MB limit and therefore
recognizable by MS-DOS.
MS-DOS applications must be specifically written to take advantage of
expanded memory. Windows applications do not use expanded memory;
80386 and newer processors can emulate expanded memory by using memory
managers such as EMM386.EXE and HIMEM.SYS.
High Memory Area
An irregularity was found in the Intel chip architecture that allowed MS-DOS
to address the first 64 KB of extended memory on machines with 80286 or
faster processors. This special area is called the high memory area (HMA). A
software driver called an A20 handler must be run to allow the processor to
access the HMA. Some versions of Windows use HIMEM.SYS for this purpose.
The only limitation is that HIMEM.SYS can load only a single program into this
area (see Figure 7.11).
Figure 7.11 High memory area
Protected Mode
Beginning with 80286 processors using an operating system such as OS/2 or
Windows, a computer can create "virtual machines," providing all the
functionality of a standard computer in real mode but allowing multiple tasks
to take place at the same time. This is called protected mode because the
processor, memory, and other hardware are protected from the software
application taking direct control of the system by the operating system, which
allocates memory and processor time.
Real Mode
In real mode (MS-DOS), a computer can perform only one operation at a time
and an application expects full control of the system. Real mode operates
within the MS-DOS 1-MB limitation.
Shadow RAM
Many high-speed expansion boards use shadow RAM to improve the
performance of a computer. Shadow RAM rewrites (or shadows) the contents
of the ROM BIOS and/or video BIOS into extended RAM (between the 640-KB
boundary and 1 MB). This allows systems to operate faster when application
software calls any BIOS routines. In some cases, system speed can be
increased up to 400 percent (see Figure 7.12).
Figure 7.12 Shadow RAM
Upper Memory Area
The upper memory area (UMA), the memory block from 640 KB to 1024 KB, is
designated for hardware use, such as video RAM, BIOS, and memory-mapped
hardware drivers that are loaded into high memory.
Determining Usable Memory
The MS-DOS command MEM (MEM.COM; still available in newer versions of
Windows, type mem in a command window) provides information about the
amount and type of memory available (see Figure 7.13). It provides a quick
way to determine how all of the different areas in physical memory are being
used and the total amount of RAM actually active on the system.
Most MS-DOS and many early Windows systems load numerous device drivers
and TSR (terminate-and-stay-resident) programs using the CONFIG.SYS and
AUTOEXEC.BAT routines during the boot cycle.
Figure 7.13 MEM.COM
NOTE
Avoid using any DOS or 16-bit TSRs in Windows 95, Windows 98,
Windows NT, Windows 2000, or Windows Me, if at all possible.
Their presence degrades system performance and can disable
some of the more advanced memory-handling features of
Windows. Properly configured, newer ver- sions of Windows 98
and beyond will not need either CONFIG.SYS or AUTOEXEC.BAT,
and some versions don't support them.
TSRs are usually loaded into conventional memory by the operating system,
taking up valuable space. Memory-management techniques are used to load
these device drivers and TSRs into the upper memory, allowing more lower
memory to be made available to applications.
To determine which device drivers and TSRs are loaded, use the command
MEM /C
The /c is a classify switch. This determines how much conventional memory a
certain real-mode program is using (see Figure 7.14).
We will cover troubleshooting and applications such as Windows System
Information in Chapter 18, "Running Microsoft Windows."
Figure 7.14 MEM /C
Lesson Summary
The following points summarize the main elements of this lesson:
Hexadecimal notation is used as shorthand for writing binary numbers.
Memory is defined in terms of the physical characteristics of the chips and
how the memory is allocated for use.
The MS-DOS operating system can address only the first 1 MB of
memory.
Expanded memory was an early method of adding memory to an MSDOS-based system. It paged, or swapped, 64-KB chunks of data through a
window (a 64-KB block of memory in the UMA) to an expansion card.
Extended memory, used by Windows 3.x and newer systems, allows the
addressing of memory above the MS-DOS limit and has virtually replaced
expanded memory.
Understanding memory allocation and the different memory locations is
key to optimizing a computer's memory.
The MS-DOS command MEM.COM is a utility that provides information
about memory allocation.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
ROM and RAM
ROM is a form of nonvolatile memory that is used in PCs to hold POST
commands.
RAM is the memory that is used by the CPU to temporarily hold data that
is currently used by the system. It is cleared any time the system is
powered down or rebooted.
RAM chips come in many sizes and shapes. It is important for the
computer technician to be able to identify the different types and
calculate how many chips, banks, or rows of memory modules are needed
to upgrade a computer.
The number of SIMMs required is based on the width of the data bus.
Memory Mapping
Memory (RAM) is allocated to different parts of the CPU. A computer
technician uses a memory map to describe how memory is allocated.
Hexadecimal numbers are used to identify the location of memory on a
memory map.
MS-DOS can access only the first 1 MB of memory.
Several commands, such as MEM.COM, are used to identify memory
allocation in a computer.
A computer technician must know the difference between conventional
and high memory.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. What is hexadecimal shorthand used for?
2. Define the following terms: conventional memory, expanded memory,
extended memory, HMA, shadow RAM.
3. Describe the difference between ROM and RAM.
4. How many 30-pin SIMM boards are required for one bank of memory on a
computer with a 486 processor?
5. What is the difference between write-through and write-back cache?
6. What is DRAM?
7. Define access speed.
8. Describe the major difference between SIPPs and SIMMs.
9. Define cache memory.
10. One of the differences between DRAM and SRAM is that SRAM does not
have to be refreshed. What does this mean, and how does it affect the
cost of each type of chip?
Answers
3 4
Chapter 8
Expansion Buses, Cables, and Connectors
About This Chapter
The success of the personal computer is due largely to its ability to expand to
meet the changing needs and economic requirements of the user. In this
chapter, we describe the array of expansion buses that help to expand the
system and work with an ever-growing number of enhancements, including
modems, video cards, and portable drives. We also discuss conflicts within the
computer—how they are created and reconciled.
A competent technician has to know how to attach new devices to a computer.
Knowledge of the different methods of doing so and the various cables used to
link devices is critical in day-to-day operations. This chapter explores the
various options and how to employ them properly and safely.
Before You Begin
This chapter requires knowledge of processors, motherboards, and the binary
and hexadecimal number systems. If you are not familiar with these concepts,
take some time to review earlier chapters.
3 4
Lesson 1: Understanding Expansion Buses
Expansion buses connect devices to the motherboard using the motherboard's
data bus. They allow the flow of data between internal and external devices
that make up the computer system. Early computers moved data between
devices and the processor at about the same rate as the processor. As
processor speeds increased, the movement of data through the bus became a
bottleneck. Therefore, the design capability of the buses needed to evolve, too.
This lesson discusses that evolution.
After this lesson, you will be able to
Identify the different types of expansion buses in a computer
Understand the difference between the system bus and the expansion bus
Estimated lesson time: 30 minutes
Development of the Expansion Bus
As discussed earlier in Chapter 4, "The Central Processing Unit," every device
in the computer—random access memory (RAM), the keyboard, network
interface card (NIC), sound card, and so forth—is connected to the external
data bus. Expansion slots on the motherboard are standardized connections
that allow the installation of devices not soldered to the motherboard. The
function of an expansion slot is to provide configuration flexibility when
devices are added to a computer.
Whether a device is soldered to the motherboard or connected through an
expansion slot, all integrated circuits (ICs) are regulated by a quartz crystal.
The crystal sets the timing for the system, giving all parts access to a common
reference point for performing actions. Most central processing units (CPUs)
divide the crystal speed by two. (If the CPU has a 33-MHz speed, a 66-MHz
crystal is required.) Every device soldered to the motherboard—keyboard chip,
memory controller chip, and so on—is designed to run at the speed (or at half
the speed) of the system crystal.
Although CPU speeds have continually increased as technology has improved,
the speeds of expansion cards has remained relatively constant. It was not
practical to redesign and replace every expansion card each time a new
processor was released—this would have been complicated and expensive for
manufacturers. (And, of course, the additional expense would have been
passed along to the consumer.) The commitment of the industry to maintain
backward compatibility further complicated design tasks because any new
technology would have to be compatible with the older, slower devices.
To resolve this dilemma, designers divided the external data bus into two
parts:
System bus. This supports the CPU, RAM, and other motherboard
components and runs at speeds that support the CPU.
Expansion bus. This supports any add-on devices by means of the
expansion slots and runs at a steady rate, based on the specific bus
design.
Dividing the bus enhances overall system efficiency. Because the CPU runs off
the system clock, upgrading a CPU requires changing only the timing of the
system bus, and the existing expansion cards continue to run as before. There
is usually a jumper setting that changes the system clock speed to match the
CPU. The ability of the motherboard to make this change sets the limit for the
processor speed. Next, we take a look at the evolving types of expansion
buses.
Industry Standard Architecture
The first-generation IBM XT (with the 8088 processor) had an 8-bit external
data bus and ran at a speed of 4.77 MHz. These machines were sold with an 8bit expansion bus (PC bus) that ran at 8.33 MHz (see Figure 8.1).
Figure 8.1 8-bit PC bus slot
When IBM designed the first PC back in 1981, it took steps that fueled the
rapid development of the PC market. IBM's engineers designed the PC as an
open system, capable of using standard, off-the-shelf components. This
allowed third-party developers to manufacture cards that could snap into the
PC bus. IBM also allowed competitors to copy the PC bus.
With this decision, IBM established the Industry Standard Architecture (ISA)
interface, thus generating the market for "clones." A host of third-party
companies developed products that enhanced the basic PC design and kept
prices much lower for add-ons than those for competing proprietary systems
such as the Apple II. Without this push, the PC market would not have
developed as rapidly as it did.
In 1984, when IBM released the AT (Advanced Technology) PC, featuring
Intel's 80286 16-bit processor, it wanted to include a new expansion bus—one
that would be compatible with previously released devices. To accomplish this,
the designers added a bus that allowed insertion of either an 8-bit card or a
16-bit card. This change resulted in the standard 16-bit ISA slot. This new 16bit bus officially ran at a top speed of 8.33 MHz, but on some Peripheral
Component Interconnect (PCI)-based systems, the actual rate for ISA slots
proved to be as high as about 10 MHz. (PCI is discussed later in this lesson.)
NOTE
The term "ISA" did not become official until 1990. Therefore, the
8-bit slot is called the XT, and the 16-bit slot is called the AT.
When we refer to an ISA slot or an ISA card, we generally mean
the 16-bit AT-style interface. The speed of the slots remained at
about 7 MHz.
Problems with the ISA Design
The ISA design is one of the most enduring elements of the PC. It can be found
on virtually all systems, from the second-generation IBM PC to machines built
today. However, it suffers from two major shortcomings: lack of speed and
compatibility problems stemming from card design.
As CPU performance increased and applications became more powerful, card
designers sought an interface that would allow add-on cards to keep up with
the need for improved hard drives, display adapters, and similar products.
Expansion cards must make use of system resources in an orderly way, so that
they do not conflict with other devices. When demands for these system
resources are not coordinated, the system could behave erratically or even fail
to boot up. Formerly, ISA cards often used a bewildering array of jumpers and
switches to set addresses for memory use or the IRQ (interrupt request)
locations they would use.
The need to overcome the expansion card's lack of speed and compatibility
problems led to a search for a new, standard expansion card interface—one
that everyone could agree on and that would gain user acceptance.
Micro Channel Architecture
In 1986 the market came to be dominated by the new 386 machines with their
32-bit architecture. Most PC manufacturers stuck to the same basic ISA design
and MS-DOS. Expansion devices based on ISA technology for the 286 AT class
machines could be placed in a new 386 clone without problems.
IBM, however, was feeling the pinch of competition from cheaper clones, and
sought to retain its dominance in the PC market. IBM designers produced a
new version of the PC, the PS/2 (Personal System/2), and created a
proprietary expansion bus called Micro Channel Architecture (MCA) as part of
the design. Running at 10 MHz, it offered more performance and provided a
32-bit data path, but was also totally incompatible with older ISA cards.
A feature of MCA was its ability to "self-configure" devices. Unlike devices that
use technology in which the PC configures itself automatically to work with
peripherals such as monitors, modems, and printers, an MCA device always
came with a configuration disk. When installing a new device in an MCA
computer, the technician inserted the configuration disk (when prompted), and
the IRQs, input/output (I/O) addresses, and direct memory access (DMA)
channels were configured automatically. (IRQs, I/O addresses, and DMA
channels are discussed in detail in the next lesson.) An MCA bus is shown in
Figure 8.2.
The PS/2 and its Micro Channel Architecture expansion bus never gained
enough market share to compete with the 386. MCA cards were few and far
between, and more expensive than competing interface designs.
Figure 8.2 MCA bus
MCA is now a lost technology. As a computer technician, you will not
encounter MCA on new computers. However, it is still found in some older
machines, and you will need to know how to identify it. If (by some rare
chance) a customer brings in a PS/2 machine for service, be sure to obtain the
configuration disks for the computer as well as any MCA cards that go with it.
Extended ISA
In 1988 an industry group answered the challenge of MCA and released a new
32-bit, 8-MHz open standard called Extended ISA (EISA—pronounced ee-suh).
EISA is an improved variation of the ISA slot that accepts older ISA cards, with
a two-step design that uses a shallow set of pins to attach to ISA cards and a
deeper connection for attaching to EISA cards. In other words, ISA cards slip
partway down into the socket; EISA cards seat farther down.
CAUTION
Be very careful to line up cards being placed in an EISA slot
precisely and push straight down! If you try to angle the card in, it
can be very difficult to seat and you might damage either the
connector or the slot.
Although EISA is faster and cheaper than MCA, it never gained much more
acceptance than MCA.
Confusion between MCA and EISA technology—along with a limited need for
cards that ran at the faster rate and the fact that only a few display, drive
controller, and network cards were made available—led to the early demise of
both bus technologies. Figures 8.3 and 8.4 show how the slot design of the two
technologies differs.
Figure 8.3 Top view of ISA and EISA bus
Figure 8.4 Cross-section of ISA and EISA bus
VESA Local Bus
The problems posed by MCA and EISA designs meant that developers needed
an improved bus architecture to speed up graphics adapter performance and
keep up with the evolving operating system technologies, such as Microsoft
Windows. The Windows graphical user interface (GUI) required a much faster
display adapter, because every pixel (not just lines of character data) had to
be represented and refreshed. About the same time, laser printers and
graphics programs like PageMaker and CorelDRAW entered the mainstream
market, extending the desktop publishing revolution. The hardware industry
developed the VESA local bus (VLB) to meet the need for a faster expansion
interface. (VESA, the Video Electronics Standards Association, was the driving
force behind the new bus technology.) Found only in 386 and 486 machines,
the VLB had a short life span. The cards based on this design are connected
directly to the system-bus side of the PC's external data bus (see Figure 8.5).
Figure 8.5 VESA local bus design
The speed of the system data bus is based on the clock rate of the
motherboard's crystal. During the heyday of the VLB, this was usually 33 MHz,
and VLB cards usually ran at half that rate, far outpacing the ISA bus. Some
cards ran as fast as 50 MHz, using the full speed of the souped-up system bus.
That often caused system crashes, because 50 MHz was outside the VLB
specification.
The chip design for the VLB controller was relatively simple because many of
the core instructions were hosted by the ISA circuits already on the
motherboard, but the actual data passes were on the same local bus as the
one used by the CPU.
The design specification provides two other performance-boosting features:
burst mode and bus mastering. In burst mode, VLB devices gain complete
control of the external data bus for up to four bus cycles, passing up to 16
bytes (128 bits) of data in a single burst. Bus mastering allows the VLB
controller to arbitrate data transfers between the external data bus and up to
three VLB devices without assistance from the CPU. This limit of three devices
also limited the maximum number of VLB slots to three and called for the use
of a coprocessor. Display-system design is covered in more detail in Chapter
11, "The Display System."
The actual connectors on the motherboard resemble an ISA slot with an
additional short slot aligned with it. On systems that support this interface,
one to three slots are located on the side of the motherboard closest to the
keyboard connection.
Peripheral Component Interconnect
PCI allows developers to design cards that will work in any PCI-compatible
machine. It overcomes the limitations of ISA, EISA, MCA, and VLB, and it
offers the performance needed for today's fast systems.
At first glance, there are many similarities between PCI and the older VLB
specifications. Both are local bus systems with 32-bit data paths and burst
modes. Also, the original PCI design operates at 33 MHz—roughly the same
speed as the VLB. However, the important differences between them allowed
PCI to dominate in expansion bus technology. These differences stem from the
following features:
The PCI design's special bus and chip set are designed for advanced busmastering techniques and full arbitration of the PCI local bus. This allows
support of more than three slots.
The PCI bus has its own set of four interrupts, which are mapped to
regular IRQs on the system. If a PC has more than four PCI slots, some
will be sharing interrupts and IRQs.
NOTE
Under Windows 95 or with poorly designed PCI cards (both are
becoming rarities), the shared addresses could lead to system
conflicts and resource problems. Installing PCI cards one at a time
minimizes these problems. Also, be aware that on many systems
not all PCI slots offer full bus mastering. Check the owner's
manual for details, especially on machines with more than four
slots. In general, the PCI slots closest to the keyboard connector
are the best choices for full bus mastering.
The PCI bus allows multiple bus-mastering devices. Advanced controllers
such as SCSI (Small Computer System Interface) cards can incorporate
their own internal bus mastering and directly control attached devices,
then arbitrate with the PCI bus for data transfers across the system bus.
Autoconfiguration lets the PC's BIOS assign the IRQ linking the card to
the system bus. Most PCI cards have no switches or jumpers to set,
speeding installation and preventing many hardware conflicts.
Most PCs on the market today have one or more ISA slots for backward
compatibility; however, most expansion cards are now built using the PCI
interface. Although Intel was the original driving force behind PCI
development, a PCI standards committee maintains the specification, and it is
an open design—meaning that anyone can design hardware using PCI without
being required to pay royalties.
Variations on a Theme: Differences in PCI Versions
The earlier discussion makes PCI sound like a technician's dream interface:
fast, reliable, and doing most of the work itself. In most cases, that's true; still,
there is always a "but." PCI has gone through many changes, and there are
some features to be aware of when you work with a PCI card:
The early PCI motherboards often have jumpers and BIOS settings that
must be set to enable proper PCI operation. These are most often found
on Pentium 60-MHz and 66-MHz machines.
The PCI bus speed is not fixed. Newer chip sets can drive it—and the
cards on it—at 66 MHz. At full performance, the PCI bus can deliver data
transfers at up to 132 MB per second.
PCI is not used only by PCs. Macintosh and some other non-PC-style
computers incorporate PCI. Manufacturers appreciate this feature because
it allows them to design core technology and port it to different models
using the same production line. You still need to be certain, however, that
a particular card is actually designed for the machine you are working on,
even if it fits.
Keep in mind that PCI is evolving. That will help to keep it a viable interface
for the foreseeable future, but it might also lead to incompatibilities between
new cards and older machines.
Accelerated Graphics Port
In the early days of PCI, the major market for that technology was the highperformance display adapter. The popularity of PCI led to its dominance of the
expansion bus market. Today, the PCI market includes NICs, sound cards,
SCSI adapters, Ultra Direct Memory Access (UDMA) controllers, and DVD
(digital video disc) interfaces. The variety of devices posed a problem for
display-card designers: Having more cards on a single bus slowed down the
performance, just when the increasing popularity of 24-bit graphics and 3D
rendering called for greater demands on the display system. The search was
on for yet another interface; this time, the solution was a single slot—tuned
for the display adapter. Once again, Intel led the way and developed the
Accelerated Graphics Port (AGP).
The AGP removes all the display data traffic from the PCI bus and gives that
traffic its own 525-MB-per-second pipe into the system's chip set and, from
there, straight to the CPU. It also provides a direct path to the system memory
for handling graphics. This procedure is referred to as Direct Memory Execute
(DIME). The AGP data path is shown in Figure 8.6.
Figure 8.6 AGP Direct Memory Execute offers priority access to display data
The AGP slot, if present, is the only one of its kind on the motherboard and is
usually the slot closest to the keyboard connector (see Figure 8.7). It is set
farther from the back of the PC's case than the PCI slots. AGP connectors are
found only on Pentium II-based and later computers or on similar CPUs from
non-Intel vendors.
Figure 8.7 An AGP slot on the motherboard
IEEE 1394 FireWire High-Performance Serial Interface
One contender that has been touted as a possible replacement for SCSI (see
Chapter 9, "Basic Disk Drives," for details on the SCSI interface) in connecting
external peripherals is IEEE 1394, known also by its Apple trade name of
FireWire. We'll use the short form and call it 1394. This high-speed serial
interface allows up to 62 devices on a chain, at data transfer rates of up to 50
MB per second.
This new interface offers several advantages: a hot swap capability (the ability
to add and remove components while the machine is running), small and
inexpensive connectors, and a simple cable design. Right now, few devices
support 1394, but it is seen as a viable method for connecting multimedia
devices like camcorders and other consumer electronic devices to PCs. Its
isochronous transfer method (sending data at a constant rate) makes it a
natural for video products. Currently, many 1394 PC products are expensive
and there is no provision for connecting internal devices. Both 1394 and SCSI
will coexist much like SCSI and universal serial bus (USB) for the foreseeable
future. (USB is discussed in the next section.)
Although there are some standards defining how connections are made with
1394, several vendors are offering custom ways of linking products.
Universal Serial Bus
The newest addition to the general PC bus collection, the USB connects
external peripherals such as mouse devices, printers, modems, keyboards,
joysticks, scanners, and digital cameras to the computer. The USB port is a
thin slot; most new motherboards offer two, located near the keyboard. They
can also be provided through an expansion card.
USB supports isochronous (time-dependent) and asynchronous (intermittent)
data transfers. Isochronous connections transfer data at a guaranteed fixed
rate of delivery. This is required for more demanding multimedia applications
and devices. Asynchronous data can be transferred whenever there is no
isochronous traffic on the bus. USB supports the following data transfer rates,
depending on the amount of bus bandwidth a peripheral device requires:
1.5 megabits per second (Mbps) asynchronous transfer rate for devices,
such as a mouse or keyboard, that do not require a large amount of
bandwidth.
12 Mbps isochronous transfer rate for high-bandwidth devices such as
modems, speakers, scanners, and monitors. The guaranteed data-delivery
rate provided by isochronous data transfer is required to support the
demand of multimedia applications and devices.
USB devices can be attached with the computer running. A new device will
usually be recognized by the operating system (assuming the operating system
has Plug and Play capability), and the user will be prompted for drivers, if
required. Bear in mind that USB is a new standard, and some early USB ports
and chip sets do not properly support some newer devices. Problems with
embedded USB ports are not generally worth repairing. It is usually better to
install a new USB interface card.
Attaching a new USB device is usually little more complicated than hooking up
the appropriate cables and loading a driver disk if requested (see Figure 8.8).
Keep in mind that older products may not be adequately supported, and that
some devices will require an external power supply.
Figure 8.8 USB connectors
Lesson Summary
The following points summarize the main elements of this lesson:
Expansion buses provide a way of connecting devices to the motherboard.
ISA could accommodate both 8-bit and 16-bit expansion cards.
MCA was a proprietary architecture for IBM's PS/2 computers.
EISA 32-bit architecture could accommodate older ISA expansion cards.
VLB architecture employed burst mode and bus mastering to boost
performance.
PCI architecture makes use of autoconfiguration to let the PC's BIOS
assign the IRQ linking the card to the system bus.
AGP architecture removes display data traffic from the PCI bus.
USB architecture supports both isochronous (time-dependent) and
asynchronous (intermittent) data transfers.
IEEE 1394 is mostly used for multimedia applications on desktop
computers.
Expansion buses have changed to keep up with increases in processor
speed.
A computer technician must know how to identify the various expansion
buses (ISA, MCA, EISA, PCI, AGP, and USB) to ensure compatibility and
know how to maximize performance when upgrading a computer.
3 4
Lesson 2: Configuring Expansion Cards
In the previous lesson, we discussed the different kinds of expansion buses.
The purpose of these buses is to accept expansion cards. Internal and external
computer hardware, such as disk drives and monitors, can be connected to the
computer's motherboard by means of these expansion cards. As we learned in
earlier lessons, the expansion buses connect to an external data bus. All
devices are connected to the same communication bus. In this lesson, we look
at how the computer keeps track of each device and controls the flow of data.
After this lesson, you will be able to
Define addresses
Describe the attributes and limitations of an IRQ
Identify the causes of conflicts within a computer
Locate and resolve hardware conflicts
Estimated lesson time: 30 minutes
I/O Addresses
The bus system establishes a connection between the CPU and expansion
devices and provides a path for the flow of data. The computer needs a way to
track and control which device is sending data and which device is receiving;
without such a means—the bus system—there would be complete chaos. The
first step to establishing orderly communication is to assign a unique I/O
address to each device.
NOTE
Everything in a computer, hardware or software, requires a unique
name and address for the CPU to be able to identify what is going
on. Bus-mastering devices might seem to get around this
requirement, but they have their own controllers that track local
traffic and "talk" to the CPU as needed.
I/O addresses are patterns of 1s and 0s transmitted across the address bus by
the CPU. The CPU must identify the device before any data is placed on the
bus. The CPU uses two bus wires—the Input/Output Read (IOR) wire and the
Input/Output Write (IOW) wire—to notify the devices that the address bus is
not being used to specify an address in memory, but rather to read to or write
from a particular device. The address bus has at least 20 wires. However,
when the IOW or IOR wire has voltage, only the first 16 wires are monitored.
To allow communication directly between the CPU and a device, each device
responds to unique, built-in patterns or code. If the CPU needs to check the
error status of a hard disk drive controller, for instance, it activates the IOW
wire and puts the correct pattern of 1s and 0s onto the address bus. The
controller then sends back a message describing its error status.
All I/O addresses define the range of patterns assigned to each device's
command set. The device ignores all commands outside its range. All devices
must have an I/O address, and no two devices can have overlapping ranges.
Basic devices on the address list have preset I/O addresses that cannot be
changed. Other devices must be assigned to the open addresses, and they
must be configured at installation. The following table lists standard PC I/O
port address assignments.
PC/XT
PC/XT
Used By
Used By
Port
Port
000h00Fh DMA chip 8237A
2F0h2F7h Reserved
020h021h PIC 8259A
2F8h2FFh COM2
040h043h PIT 8253
300h31Fh Prototype adapter
060h063h PPI 8255
320h32Fh Hard disk controller
080h083h DMA page register
378h37Fh Parallel interface
0A0h0AFh NMI mask register
380h38Fh SDLC adapter
0C0h0CFh Reserved
3A0h3AFh Reserved
0E0h0EFh Reserved
3B0h3BFh
100h1FFh Unused
3C0h3CFh EGA
200h20Fh Game adapter
3D0h3DFh CGA
210h217h Extension unit
3E0h3E7h Reserved
220h24Fh Reserved
3F0h3F7h Floppy disk controller
278h27Fh Parallel printer
3F8h3FFh COM1
AT Port
Used By
Monochrome
adapter/parallel interface
AT Port
Used By
000h00Fh First DMA chip 8237A
278h27Fh Second parallel interface
020h021h First PIC 8259A
2B0h2DFh EGA
040h043h PIT 8253
2F8h2FFh COM2
060h063h
Keyboard controller
8042
300h31Fh Prototype adapter
070h071h Real-time clock
320h32Fh Available
080h083h DMA page register
378h37Fh First parallel interface
0A0h0AFh Second PIC 8259A
380h38Fh SDLC adapter
0C0h0CFh
Second DMA chip
8237A
0E0h0EFh Reserved
0F0h0FFh
Reserved for
coprocessor 80287
3A0h3AFh Reserved
3B0h3BFh
Monochrome
adapter/parallel interface
3c0h3CFh EGA
100h1FFh Available
3D0h3DFh CGA
200h20Fh Game adapter
3E0h3E7h Reserved
210h217h Reserved
3F0h3F7h Floppy disk controller
220h26Fh Available
3F8h3FFh COM1
I/O addresses have several important characteristics to remember:
I/O addresses have 16 bits; they are displayed with a hexadecimal
number.
By convention, the lead 0 is dropped (because all I/O addresses have it).
Hexadecimal I/O addresses must use capital letters; they are casesensitive.
Setting I/O Addresses
Run the Jumpers video located in the Demos folder on the CD accompanying
this book to view a presentation of how jumpers are used to configure
expansion cards.
As mentioned, each device in a computer must have an I/O address. If a
device qualifies as a basic device, it will have a standard, preset I/O address.
The default setting for the I/O address will work and no changes are required.
If a device is not a basic device, and does not conform to the PCI Plug and Play
specification on a Plug and Play–compatible system, read the manual that
came with it. The manual will explain how to set the I/O address and define
the limits for that device.
On non-Plug and Play devices, I/O addresses are often set by changing
jumpers, changing DIP switches, or through use of software drivers. DIP
switches are like mini-rocker panel switches. Jumpers are small caps that are
used to link pairs of pins to close a circuit. Devices using these techniques
should have instructions on how to configure the settings and locate the switch
block or jumpers.
On Plug and Play systems, PCI cards are self-configuring, and usually no
intervention is needed to set I/O addresses for those cards. It is possible for
Plug and Play cards to conflict with older ISA cards that don't recognize the
Plug and Play devices. If you are confronted with this problem, refer to the
cards and the motherboard manual for possible resolution.
Managing I/O Addresses
Devices assigned overlapping I/O addresses usually do not respond to
commands and stop functioning. In such a scenario, a modem will dial but not
connect; a sound card will start to play but will stop; a mouse pointer will
appear but the mouse will not move. I/O overlaps can also sometimes cause
the machine to lock up intermittently.
I/O overlaps never happen independently. They usually appear immediately
after a new device is installed. The best way to prevent I/O address overlaps is
to document all I/O addresses. There are many commercially available
programs that will check the I/O addresses for every device on your computer.
You can also use Microsoft Diagnostics, a program provided with MS-DOS.
NOTE
If you are running Windows 95 or Windows 98, Windows Me,
Windows NT, or Windows 2000, you can use the Device Manager
or System Information to locate and resolve IRQ and address
conflicts. (See Chapter 16, "Operating System Fundamentals," for
more information on the Device Manager.)
Interrupt Request
The I/O address and the address bus establish a method of communication.
The next step is to prevent multiple devices from "talking" at the same time. If
the CPU needs to communicate with a device, BIOS routines or device drivers
can use I/O addresses to initiate conversations over the external data bus.
Controlling the flow of communication is called interruption. Every CPU has a
wire called the interrupt (INT) wire. If voltage is applied to the wire, the CPU
interrupts what it is doing and attends to the device. For example, when a
mouse button is pressed, the CPU attends to the interrupt request, invoking
the necessary BIOS routine to query the mouse.
Because the CPU has only one INT wire and must handle many peripheral
devices, a specific type of chip, called the 8259 chip, is present on the system
to help the CPU detect which device is asking for attention. Every device that
needs to interrupt the CPU is provided with a wire called an IRQ. If a device
needs to interrupt the CPU, it goes through the following steps:
1. The device applies voltage to the 8259 chip through its IRQ wire.
2. The 8259 chip informs the CPU, by means of the INT wire, that an
interrupt is pending.
3. The CPU uses a wire called an INTA (interrupt acknowledge) to signal the
8259 chip to send a pattern of 1s and 0s on the external data bus. This
information conveys to the CPU which device is interrupting.
4. The CPU knows which BIOS to run.
The 8088 computers used only one 8259 chip (see Figure 8.9), which limited
these computers to using only eight available IRQs. Because a keyboard and
system timer were fixtures on all computers, these IRQs were permanently
wired into the motherboard. The remaining six wires were then made part of
the expansion bus and were available for use by other devices.
Figure 8.9 8259 chip with IRQ assignments
Starting with the generation of computers based on the 80286 chip, two 8259
chips were used to add 8 more available IRQs (see Figure 8.10). These new
wires were run to the extension on the 16-bit ISA expansion slot (the 8-bit XT
slot was extended to a 16-bit XT slot). Because the CPU has only one IRQ wire,
one of the IRQs is used to cascade the two 8259 chips together. This gives a
total of 15 available IRQs.
NOTE
When a device is cascaded, this means that data is passed through
a common path between two devices, usually on to another
destination. The term denotes a situation much like water
cascading over a waterfall on its journey to the sea.
Figure 8.10 Cascading 8259 chips
Notice that the cascade removes IRQ 2. IRQ 9 is directed to the old IRQ 2 wire.
Any older device designed to run on IRQ 2 will now run on IRQ 9. Some
important facts to remember about IRQs include the following:
IRQ 2 and IRQ 9 are the same IRQ.
Three IRQs are hardwired (0—system timer, 1—keyboard controller, and
8—real-time clock).
Four IRQ assignments are so common that no computer or device
manufacturer dares to change them for fear their devices will cause
conflicts (6—floppy disk controller, 13—math coprocessor, 14—primary
IDE [Integrated Device Electronics] controller, and 15—secondary IDE
controller).
Four IRQs default to specific types of devices but can be changed: IRQ 3—
COM2 and COM4, 4—COM1 and COM3, 5—LPT2, and 7—LPT1 (see table
that follows).
The rest (IRQs 2/9, 10, 11, and 12) are not specific and are available for
use.
NOTE
The 8259 chips no longer exist on a motherboard. Their functions
have become part of the multifunction chips called chip sets that
perform all the functions of the 8259 chips and more. However,
the information provided in the preceding section is still useful for
understanding how this portion of the chip set operates. Also, the
IRQ assignments generally are the same.
The following table provides typical IRQ assignments.
IRQ
Function
Available for Change
IRQ 0
System timer
No
IRQ 1
Keyboard controller
No
IRQ 2/9
Available
Yes
IRQ 3
COM2, COM4
Usually
IRQ 4
COM1, COM3
Usually
IRQ 5
LPT2
Usually
IRQ 6
Floppy disk controller
No
IRQ 7
LPT1
Usually
IRQ 8
Real-time clock
No
IRQ 10
Available
Yes
IRQ 11
SCSI/available
Yes
IRQ 12
Available
Yes
IRQ 13
Math coprocessor
If there is no math coprocessor
IRQ 14
Primary IDE controller
No
IRQ 15
Secondary IDE controller
Usually
Setting IRQs
Devices lacking a fixed or standard IRQ (except for newer PCI cards in
compatible PCs) must have their IRQs set during installation. Read the
accompanying manuals to learn about these devices. Setting IRQs is one of the
first topics discussed in any device's installation instructions. The manual will
tell you not only how to set the IRQ, but also the limits, if any, of the device.
Just like I/O addresses, IRQs can be set using hardware, software, or a
combination of both. The best way to ensure that no two devices share the
same IRQ is to document the IRQs for each device you install in a computer
and file that documentation in a location where you can find it easily if
needed. As an example, suppose one of your customers has recently installed
a sound card that now locks up when a parallel-port tape backup unit is used
on the system. This strongly indicates an IRQ conflict. You need merely to
check the sound card and the tape backup IRQ settings you have on file and
change one if necessary.
IMPORTANT
Some devices have a limited number of IRQ settings; you might
need to change the IRQs of other devices to free one of these
IRQs.
Direct Memory Access
The CPU runs the BIOS, operating system, and applications, and it also
handles interrupts and accesses I/O addresses. This requires the CPU to move
a lot of data, using considerable CPU power and time for what is essentially a
simple task. Therefore, moving data is a waste of the CPU's resources.
To reduce this waste, another chip is installed to work with the system CPU
called a DMA chip. The only function of the DMA chip (the 8237 chip) is to
move data. It handles all the data passing from peripherals to RAM and vice
versa.
DMA transfers are not automatic. Hardware and device drivers must be
designed to take advantage of this chip. Originally, DMA was used only to
transfer data between floppy disk drives and RAM; early computers had only
four wires and one DMA chip. Any device requiring DMA had to send a request,
just like an IRQ.
DMA channels use the same rules as IRQs. Just as with the 8259 chip, DMA
availability soon became a problem because an insufficient number of channels
was available. A second DMA chip was added for 80286-based computers. Just
like the second IRQ chip, these two are cascaded, allowing a total of eight DMA
channel assignments (usually referred to simply as DMA channels). Every
computer uses DMA 2 for the floppy disk drive.
Setting DMA Channels
Fortunately, not many devices use DMA, but sound cards, a few SCSI
controllers, and some CD-ROM drives and network cards do require DMA. Just
as with IRQs and I/O addresses, DMA can be set by means of either hardware
or software. However, manufacturers started using DMA for devices other than
the floppy disk drive only recently. As a result, almost all devices set DMA
through software (although some still use jumpers). If two devices share the
same DMA channel and "talk" at the same time, the computer will lock up. The
following table provides DMA channel assignments.
DMA Channel
Function
0
Available
1
Available
2
Floppy disk controller
3
ECP (Enhanced Capabilities Port) parallel/available
4
First DMA controller
5
Second sound card
6
SCSI/available
7
Available
Managing DMA
DMA and IRQ work in the same way; therefore, DMA conflicts look and act
exactly like IRQ conflicts. Always check for IRQ conflicts first (although it is
possible for a computer professional to spend hours trying to solve IRQ
problems when the source of the problem is actually the DMA). If you are sure
all IRQs are correct, yet the computer continues to experience a problem,
check the DMA. There is very little diagnostic software for resolving DMA
problems, so it is important to maintain careful documentation.
COM and Ports
IBM created preset combinations of IRQs and I/O addresses for serial and
parallel devices. These preset combinations are called ports. The word port
simply means a portal or two-way access. The preset combinations are called
COM ports for serial devices and LPT (line printer) ports for parallel devices.
The purpose of a port is to make installation easier. Modems and printers,
therefore, do not require IRQ or I/O settings. When assigned to an active port
(as long as no other device is using that port), they will work. The following
table lists standard ports.
Port
I/O Address
IRQ
COM1
3F8
4
COM2
2F8
3
COM3
3E8
4
COM4
2E8
3
LPT1
378
7
LPT2
278
5
Most computers are manufactured to offer built-in physical ports with cable
connections available either directly to the motherboard or in an expansion
slot. In this case, the standard port addresses and IRQs are assigned to them.
This makes it possible to install an external device simply by plugging in the
port and assigning addresses to the device. If necessary, these ports can be
disabled (by using CMOS setup), freeing their I/O addresses and IRQs for
another device.
For example, suppose you want to install a new internal modem on a machine
that has two external serial ports on the motherboard. By disabling one of
these ports, you have made its address and IRQ available for use by the
internal device. Simply assign the device to the port that is now free.
Installation Problems with COM Ports
Assume you have a modem set to COMl. You buy a network card that comes
out of the box with a default setting of IRQ4. You realize the network card and
the modem will conflict, and the computer will lock up. What should you do?
You should change the IRQ on one of the devices. The network card is
probably the best choice, because the modem is installed and already working.
COM Ports
The original 8088-based IBM PCs were equipped with two serial ports: COMl,
set to IRQ4, and COM2, set to IRQ3. Although those two IRQs are still the
standard for COM ports 1 and 2, many BIOS routines will allow different IRQ
assignments or even allow an unused port to be disabled. Because of the
limited number of IRQ addresses available, any additional COM ports would
have to share IRQs with existing ports. COM3 shared the interrupt of COM1
(IRQ4), and COM4 shared the interrupt of COM2 (IRQ3). To enable use of
these additional ports, COM3 was assigned I/O address 3E8-3EF, and COM4
was assigned I/O address 2E8-2EF. This sharing was possible because the IRQsharing devices would be unlikely to use them at the same time.
Today we have many other ways of adding printers and other peripherals to
PCs, but such conflicts can still be a problem with modems and UPS
(uninterruptible power supply) devices that might need simultaneous access.
NOTE
The first rule for setting IRQs is to ensure that two devices never
share the same IRQ. The only exception is that two (or more)
devices can share an IRQ if they never "talk" at the same time.
Common IRQ conflicts occur among a serial mouse, sound card,
modem, and/or serial printer. (Remember that PCI devices can
share an IRQ if the IRQ is managed by the same PCI controller.)
LPT Ports
LPT ports are for parallel data connections. The name is derived from their
original use with printers. The original IBM standard LPT port did not provide
bidirectional communications (talkback) and was designed solely for one-way
data streams to a printer. The standard addresses are IRQ7 for LPT1 and IRQ5
for LPT2, if it is present. IRQ5 quickly became the favorite for devices like
sound cards and other add-ons. Today, many devices are made that can use
the parallel plug in the back of a computer, thus reducing costs. These devices
(tape backups, SCSI drives, or modems) use bidirectional communication and,
therefore, need an interrupt. This situation is easing as USB connections
replace many of the parallel designs.
Installing Expansion Cards
The rules for installing expansion cards are simple:
First read the manual.
Document addresses and DMA and IRQ settings for any non-Plug and Play
device.
Keep the IRQs, DMAs, and I/O addresses unique.
Windows 95, Windows 98, Windows Me, and Windows 2000 support Plug and
Play. In most cases, you can insert a Plug and Play card into the proper type of
expansion slot and turn on the computer. Windows will find the card and guide
you through the setup. The savvy computer professional documents and keeps
track of the IRQ, DMA, and I/O addresses, in case a conflict arises with a Plug
and Play device on the system.
Windows 95, Windows 98, and Windows Me use Hardware Properties, under
the System option in the Control Panel, which does a good job of identifying
(and allowing) changes to these settings. To view assignments, from Control
Panel, select System, select the Device Manager tab, and then click Properties.
TIP
A good way to document a computer is to print a complete list of
the computer's hardware settings, listed in the Computer
Properties dialog box.
NOTE
For Plug and Play to work, the computer must have a Plug and
Play BIOS, and the operating system and the device card must be
Plug and Play–compliant.
Lesson Summary
The following points summarize the main elements of this lesson:
Every device in a computer needs a unique name and address.
In order for the CPU to identify which devices need to use the data bus, it
monitors the IRQs.
Generally, no two devices can use the same IRQ or DMA channel.
Most conflicts during installation of a new device are caused by IRQ
conflicts.
BIOS routines or device drivers can use I/O addresses to initiate
"conversations" over the external data bus by means of an IRQ.
DMA handles all the data passing from assigned peripherals to RAM and
vice versa.
COM ports are for serial devices; LPT ports are for parallel devices.
The computer technician should document addresses and DMA and IRQ
settings for any non-Plug and Play device installed in a computer.
3 4
Lesson 3: Cables and Connectors
Cables and connectors are critical to the operation of any computer
peripherals. A computer professional must be able to identify and understand
the various types of cables and connectors. This lesson discusses common
connectors and their functions.
After this lesson, you will be able to
Identify cables and connectors by their names and functions
Estimated lesson time: 20 minutes
Parallel Printer Cables
Parallel printer ports and cables are used to connect printers and other add-on
items such as CD-ROM drives, tape drives, and scanners. Centronics
Corporation invented the most common type. It is an 8-bit parallel connection
with handshaking signals between the printer and the computer—these tell the
computer when to start or stop sending data. A standard printer cable is
configured with a 36-pin Centronics connector on the printer end and a
standard 25-pin "D" (male) on the computer end. A standard 25-pin "D"
(female) connector found on the back of the computer designates it as a
parallel port (see Figure 8.11).
Figure 8.11 Standard 25-pin D connector
The original parallel port was designed only to send information to printers and
was unidirectional. However, some bidirectional communication was possible
by manipulating the handshaking lines. Today, computer manufacturers have
developed updated versions that allow better bidirectional communication
while maintaining the original Centronics specification. The Institute of
Electrical and Electronic Engineers (IEEE) developed a standard—IEEE 1284—
to oversee the standardization of these ports.
There are three bidirectional standards used today:
Bi-Tronics. This modified Centronics connection was created by HewlettPackard. It utilizes bidirectional communication, allowing the printer to
send messages to the computer (out of paper, paper jam, and so forth).
EPP (Enhanced Parallel Port).This features 2-MB-per-second datatransfer rates, bidirectional 8-bit operation, and addressing to support
multiple (daisy-chained) peripherals on a single computer.
ECP (Extended Capabilities Port). This was developed by HewlettPackard and Microsoft. It features 2-MB-per-second data transfer and
bidirectional 8-bit operation. ECP will specify whether transmitted
information consists of data or commands for the peripheral. ECP supports
CD-ROM drive and scanner connections, run length encoded (RLE) data
compression, and DMA support to increase transfer speed and reduce
processor overhead.
NOTE
The EPP and ECP standards often have to be enabled in the CMOS
setup before the specified port can use them.
IEEE 1284 Printer Modes
A vast array of printers is available, and to ensure that you are obtaining
optimum performance, the printer, the printer driver, and the software using
the printer must be configured for the same mode. The following table
describes various printing modes and their capabilities.
Mode
Capabilities
8-bit output;
Compatibility hardware
handshaking; no DMA
4-bit
8-bit
ECP
EPP
Speed
100-200 KB per
second out
4-bit input using some 100-200 KB per
of the printer's
second out; 40-60
handshaking lines
KB per second in
Notes
Original
parallel port
HewlettPackard BiTronics mode
80-300 KB per
second
Original
bidirectional
port
8-bit I/O; can use
DMA
>2 MB per second
Scanners
and highspeed
printers
8-bit I/O
Up to 2 MB per
second
Very flexible
modes of
operation
8-bit I/O bidirectional
Parallel Pin Assignments
Just like modem cables, it is important for printer cables to have the correct
pin connections. The following table describes the standard parallel pin
assignments for the computer-end (25-pin) and the printer-end (Centronics)
connectors.
Computer Direction of Printer
DataFlow
Name
ID
Function
Sends data to
printer
1
→
1
Strobe
STROBE
2
→
2
Data bit 0
DB0
3
→
3
Data bit 1
DB1
4
→
4
Data bit 2
DB2
5
→
5
Data bit 3
DB3
6
→
6
Data bit 4
DB4
7
→
7
Data bit 5
DB5
8
→
8
Data bit 6
DB6
9
→
9
Data bit 7
DB7
10
←
10
Acknowledge ACK
11
←
11
Printer busy
BUSY
12
←
12
Paper error
PE
13
←
13
Select
SLCT
14
←
14
Autofeed
AUTOFD
15
←
32
Error
ERROR
16
→
31
Initialize
printer
INIT
17
←
36
Select input
SLECT
IN
—
←
18
5v
18-25
←
16, 19Ground
30, 33
Printer
acknowledges
receipt of
data
Indicates
printer is
online
5 volts
available from
some printers
Sometimes to
pin 17
Serial Port Cables
A serial port allows a computer to send data over long distances by converting
parallel data to serial data. Typical computers will have one or two serial ports,
usually designated as COM1 and COM2. The "standard" port is a 9-pin male
connector on the computer, shown in Figure 8.12. (There are also 25-pin
cables available.)
Figure 8.12 Standard 9-pin D connector
The following table describes the pin connection for the 9-pin and 25-pin serial
cable connectors.
9Pin
25Pin
Name
ID
Function
1
Shield
3
2
Transmit data
TD
Data sent from computer
2
3
Receive data
RD
Data sent to computer
7
4
Request to send RTS Computer is ready to send
8
5
Clear to send
CTS "Other end" is ready to receive
6
6
Data set ready
DSR "Other end" is ready to receive
5
7
Signal ground
SG
GND
1
8
Data carrier
detect
DCD
Modem detects a signal from another
modem
4
20
Data terminal
ready
DTR Computer is ready to send
9
22
Ring indicator
RI
Modem detects line ringing
Null Modem Cables
Null modem cables are used to directly connect two computers together
without the need for a modem. The transmit and receive wires in the cable
(wires 2 and 3) are switched to make the computers "think" they are using
modems.
SCSI Cables
SCSI cables come in a variety of sizes depending on the type of SCSI used and
the manufacturer of the device. Typically, internal cables are flat ribbon types
and external cables are shielded bundles.
Keyboard Cables
Another peripheral device with a cable that we encounter and yet never think
about is the keyboard. Because there are different types of keyboard cables
(and connectors) and because, on occasion, the technician might encounter a
problem with a keyboard connector, they are worthy of mention.
Keyboards are manufactured in two different styles with different cables and
connectors. Earlier versions used a 5-pin DIN connector (DIN stands for
Deutsch Industrie Norm, the German national standards organization), and
most new keyboards use a 6-pin DIN connector, the same used on a PS/2
mouse. Connectors are available to convert the 5-pin DIN to a 6-pin mini-DIN.
Although they have a different number of pins, they use the same wires and
pinouts. Data is sent serially to the keyboard using the keyboard interface.
Data is written to the controller's input buffer to accomplish this. Keyboard
data passes through pin 2 of the connector, and clocking signals move through
pin 1. A keyboard reset, which can be connected to the system's reset line, is
included at pin 3. Ground and +5-volt DC connections are applied to the
keyboard through pins 4 and 5.
Identifying Cables and Connectors
Because printers and modems can both use 9-pin and 25-pin connectors and
cables, a computer technician must be able to identify the function of the
cables by their connectors. Other devices, such as monitors and game ports,
use 15-pin connectors. Cable identification can be confusing, but it is
important. The following table summarizes how to identify common cables and
connectors.
Function
Computer Connector
Cable Connector
Communication
9-pin or 25-pin male
(serial)
9-pin or 25-pin female
Printer
(parallel)
25-pin female
Centronics 36-pin female
Monitor (VGA
and SVGA)
15-pin female (three rows of 15-pin male (three rows
pins)
of pins)
Monitor (MGA
and CGA)
9-pin female
9-pin male
Game port
(joystick)
15-pin female (two rows of
pins)
15-pin male (two rows of
pins)
Keyboard
5-pin DIN female or 6-pin
DIN female (PS/2)
5-pin DIN male or 6-pin
DIN male (PS/2)
Troubleshooting Cables
Cables and connectors are a very common source of problems. Here are a few
suggestions for troubleshooting:
If a peripheral device doesn't work, always check the cables, especially if
the device has been working recently.
Always check for loose connections.
Check for bent or broken pins on the connector. Bent pins can sometimes
be repaired; however, they will always be susceptible to damage later,
because the pin has been weakened. It is a good idea to mark these
connectors and use them with care. A better idea is to replace them.
If a connector or cable doesn't fit or if you have to push hard to make the
connection, something is wrong. Either a connector has been damaged or
it is not the right match.
Check for worn or frayed cables. Replace if necessary.
Make sure you have the right cable. Some, such as null modem cables,
look just like standard communication cables, but will not work with a
modem.
Always be wary of "homemade" cables.
Summary of Connectors
Computers use a large variety of connectors for various peripherals. The
following table offers a summary of the most common connectors and their
uses.
Name
Uses
DB-9
Serial ports—external modem, mouse, printer.
DB-25
Parallel port—printer, scanner, removable drive.
RJ-11
Standard telephone connector—2 wires.
RJ-12
Standard telephone connector—4 wires—used with dual
phone connections.
RJ-45
Network connector.
PS/2
(miniDIN)
Mouse, scanners, and some keyboards.
Centronics Printers.
USB
Technology that allows multiple peripherals to be attached to
one cable. Popular devices are keyboards, mouse devices,
modems, video cameras, and external Zip drives.
Lesson Summary
The following points summarize the main elements of this lesson:
There are many different types of computer cables and connectors. It is
important for the computer technician to be able to identify each of them.
The evolution of a technology often brings modification to cables, the way
they are wired, and their lengths.
Distinguishing between a male and a female connector is often the key to
identifying the connector's function.
Loose or poorly connected cables are often the cause of computer
problems.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Understanding Expansion Buses
Expansion slots are standardized connections that provide a common
access point for installing devices.
The different types of expansion bus architecture are ISA, MCA, EISA,
VESA VLB, and PCI.
USB architecture supports both isochronous (time-dependent) and
asynchronous (intermittent) data transfers.
PCI architecture makes use of autoconfiguration to let the PC's BIOS
assign the IRQ linking the card to the system bus.
AGP architecture removes display data traffic from the PCI bus.
Configuring Expansion Cards
For a CPU to keep track of its devices and communicate with them, a
unique I/O address must be assigned to each device.
To prevent devices from "talking" to the CPU at the same time, an IRQ
number is assigned to the devices to inform the CPU which device is
requesting its attention. It is recommended that you memorize as many
of the typical IRQ assignments as possible.
The DMA chip moves data, handling all the data passing from peripherals
to RAM and vice versa.
To avoid problems similar to IRQ conflicts, no two devices should have the
same DMA channel assignment. COM ports are used for serial devices
(such as modems) and LPT ports are used for parallel devices (such as
printers). COM ports put these devices in direct communication with the
CPU and make installation easier.
Cables and Connectors
There are many different types of computer cables and connectors. It is
important for the computer technician to be able to identify each of them.
Distinguishing between a male and a female connector is often the key to
identifying the connector's function.
Loose or poorly connected cables are often the cause of computer
problems.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Why does a computer need an expansion bus?
2. Name the available expansion buses.
3. What happens if two non-PCI devices use the same I/O address?
4. How many IRQs are available on most PCs?
5. Under what conditions would a second modem—installed and assigned to
COM3—not work?
6. Identify the two divisions of the external data bus and describe the
purpose of each.
7. What is the standard that governs computer buses?
8. What is the difference between ISA and EISA cards?
9. Why was VESA created?
10. What is bus mastering?
11. Describe ways in which the PCI bus is better than previous technologies.
12. How does the CPU use I/O addresses?
13. What is the I/O port address of COM2?
14. What are the functions of IRQs?
15. List as many of the standard IRQ assignments as you can.
16. What is the function of the DMA chip?
17. Why is it important not to assign an IRQ to more than one device?
18. What is the difference between COM ports and LPT ports?
19. Why is it important to document IRQs, DMAs, and I/O addresses?
20. Identify as many cables and connectors as you can.
21. What type of connector is used for a parallel port on the computer?
22. Describe a null modem cable.
23. What type of connector is used for a parallel port on the printer?
24. Describe a USB connector.
Answers
3 4
Chapter 9
Basic Disk Drives
About This Chapter
This chapter is all about drives—disk drives—that come in assorted sizes and
shapes. The first disk drives were physically large, small in capacity (limited in
the amount of data they could store), and very expensive. Today, disk drives
are physically small, large in capacity, and (compared to early drives) very
inexpensive.
The history of disk drives is long and complex. In this chapter, we begin our
exploration by first looking briefly at the history and development of disk
drives. We start with the most basic of drives (the floppy disk drive), and
continue through the early hard disk drives, examining their complexities and
limitations along the way.
Before You Begin
Before starting this chapter, you should review the discussions of memory,
hexadecimal notation, and basic input/output system (BIOS) operations in
Chapter 6, "Motherboard and ROM BIOS," and Chapter 7, "Memory."
3 4
Lesson 1: Floppy Disk Drives
The most basic input device is the floppy disk drive. It is perhaps the only
computer component that has retained its original technology. Other than
increased storage capacity and the adoption of a hard plastic shell, the floppy
disk drive still works essentially the same way (in terms of cabling and BIOS
configuration) it did 15 years ago. In this lesson, we explore this venerable
standard.
After this lesson, you will be able to
Describe floppy disk drive technology
Troubleshoot a floppy disk drive problem
Estimated lesson time: 20 minutes
The Basics of Floppy Disk Drives
In 1972, IBM developed the first floppy disk drives for its System 370
machines. These drives used 8-inch floppy disks. Other companies, such as
Wang, adapted the same basic design for its dedicated word processing
machines used in the 1970s and 1980s. The actual disks came pre-formatted,
and only worked on a given operating system or computer. This resulted in
high-cost drives and reduced the ability to use floppies as a quick means of
transporting files from one system to another.
When IBM introduced the personal computer (PC) in 1981, it came standard
with a 5.25-inch floppy disk drive. Floppy disks were included in PCs before
hard disk drives, mostly out of economic considerations. The cost of an early
PC hard disk drive was more than the total cost of a system today and took
half of a day to prepare and install. Some very old PCs may have a 5.25-inch
drive installed. The only reason a newer machine might need one is to
maintain compatibility with an old program or data stored on such disks.
Today's 3.5-inch floppy disks (see Figure 9.1) are made of flexible plastic and
coated with a magnetic material. To protect the disk from dust and physical
damage, it is packaged in a plastic or coated paper case. The main reason for
the popularity of floppy disk drives and disks is that they provide inexpensive
read/write (R/W) removable media. The data stored on a floppy disk can be
moved from one computer to another, provided both have the same type of
drive. In general, it is a good idea to protect your data by always keeping two
copies of any data file that you create (the original and a backup), and the
floppy disk is an excellent medium for backing up, storing, or distributing
copies of relatively small files, such as word processing documents.
Figure 9.1 Floppy disks
The following table describes various floppy disks and their capacities.
Disk
Capacity
Size
Description
5.25
160 KB
inch
Single-sided, single-density—the first model.
5.25
360 KB
inch
Double-sided, single-density.
5.25
720 KB
inch
Double-sided, double-density.
5.25
1.2 MB
inch
Double-sided, high-density.
3.5
inch
720 KB
Double-sided, double-density.
3.5
inch
1.44 MB
Double-sided, high-density—today's standard.
2.88 MB
Double-sided, quad-density. This format has never really
gained in market share and is not common on today's
PCs.
3.5
inch
The only major differences between the 5.25-inch and the 3.5-inch disk drives
(other than physical size) are that the 5.25-inch drive has a slot connector and
the 3.5-inch drive has a pin connector for engaging and spinning the disk, and
they use different power plugs and voltages.
All floppy disk drives are connected to the motherboard's external data bus by
a 34-lead ribbon cable, shown in Figure 9.2. This cable has a seven-wire twist
in lines 10 through 16. This ensures that when two floppy disk drives are
attached, the drive-select and motor-enable signals on those wires can be
inverted to "select" which drive becomes the active target. The remaining
wires carry data and ground signals. The connector end of the cable with the
twist always goes toward the drives.
Figure 9.2 Floppy disk drive cable with a twist
Early PC BIOS logic was developed to recognize one or two floppy disk drives.
In such systems, no more than one 34-pin cable for floppy disk drives can be
installed in the computer without resorting to special hardware. When a floppy
disk drive is installed on the end connector (near the twist), the drive is
logically designated as the first or primary or A drive by the BIOS. The drive
attached in the middle of the cable is always the secondary or B drive. The
BIOS will not recognize a B drive unless an A drive is physically installed.
The number 1 red wire must be connected to the number 1 pin on the drive. If
this is not correctly installed, the drive will not work (although no permanent
damage can be done by installing the connector backward).
TIP
If you install a new drive and notice that the indicator light comes
on and stays on, the cable is most likely backward.
The power connection for a floppy disk drive, shown in Figure 9.3, is either the
large, Molex-type connector on the 5.25-inch drive (see Lesson 1 of Chapter 5,
" Power Supplies," for details) or the smaller mini connector on the 3.5-inch
drive. Older power supplies may only have the Molex connections, and you will
need an adapter to attach a 3.5-inch drive. Newer power supplies, and all
power supplies for the ATX-style cases, should have both Molex and the twostrand connection for providing a 5-volt power connection to the 3.5-inch
drive.
Figure 9.3 Floppy disk drive cable connections
After you physically install a floppy disk drive, you need only use the BIOS
Setup program to adjust the proper CMOS (complementary metal-oxide
semiconductor) settings for the type and position (first or second), and the
installation will be complete. In CMOS setup, select the drive (A or B) and
enter the correct capacity.
NOTE
Very old CMOS chips won't have settings for 1.44-MB or 2.88-MB
3.5-inch floppy disk drives because they were developed before
these drives were introduced. Today the 5.25-inch drives are
obsolete, and the CMOS of the future might not have settings for
them. Several third-party utilities will allow the CMOS to accept
the necessary values to support these drives.
Keeping a Floppy Disk Drive Running
Although floppy disk drives are usually rugged and dependable, they do take a
lot of abuse and sometimes they fail. Some failures are simply caused by
improper use, some by overuse combined with a lack of cleaning, and sometimes the mechanism just stops working.
Floppy disk drives are one of the most fragile parts of a computer system.
They are highly susceptible to failure because their internal components are
directly exposed to the outside world. Often, there is only a small door or slot
that separates the R/W heads from dust, grime, and cigarette smoke. Floppy
disk drives are often the victims of inverted disks, paper clips, and other
foreign objects that can cause mechanical damage.
The good news is that floppy disk drives are inexpensive and easy to replace.
The only preventive maintenance required is to keep the floppy disk drive
clean! Excellent cleaning kits are available in most computer and discount
stores. To achieve the best performance from a floppy disk drive in a high-use
or industrial environment, schedule monthly cleaning.
Always an Exception
One unusual floppy disk drive solution that appeared during the time that the
3.5-inch models gained dominance was the hybrid 3.5/5.25 drive. This married
the slots for both formats in a single housing. These installed just like a single
drive, but the chances of coming across such a drive today are pretty rare.
Errors Caused by the Floppy Disk
If a floppy disk drive doesn't work, the first thing you should suspect is the
floppy disk. To check a floppy disk, use the following procedure:
1. First, make sure the disk is not write protected. The hole on the right top
corner of a 3.5-inch disk (viewed from the front) should be closed. On a
5.25-inch disk, the notch on one side should be visible (not covered).
2. Try another disk.
3. Try a new (formatted) disk.
4. Try someone else's disk—one that is known to work on another computer
(first make sure there is no critical data on the disk).
5. If two or more disks are unreadable, the drive is suspect; try going to MSDOS and reading a directory using the DIR command.
CAUTION
Never test a drive by using a disk that contains important data! If
the drive is bad, it may destroy any disks placed into it.
Detecting Data Errors on a Disk
If you can read data from one disk, but not another, or if a disk is very slow
reading or writing data, the problem is the floppy disk. Throw the offending
disk away. Data errors on floppy disks generally result in an error message
that ends with the words "Abort, Retry, Fail." The system will make 10
attempts to read data from a drive before reporting an error. If you get an
error, it indicates that the disk is in pretty bad shape. Transfer the data as best
you can to another drive, and discard the old disk.
The process for repairing floppy disks is identical to the process for repairing
hard disk drives, should there be data on the disk that must be recovered (see
"ScanDisk" in Lesson 2, later in this chapter).
Check the CMOS Setting
Occasionally, the CMOS settings for floppy disks cause problems with drive
operations. Any of the following errors indicates a possible CMOS setup
problem:
General failure reading drive A: (or B:)
Not ready error reading drive A: (or B:)
Insert disk for drive A: (or B:) and press any key when ready
BIOS makers often use the 3.5-inch high-density disk drive as the default
CMOS setting for the A drive. With this BIOS, failure of the CMOS battery, or
even accidental erasure of the CMOS, will still allow most floppy disks to work.
Always double-check the CMOS if you are experiencing a recurrent floppy disk
drive failure. It is quick, easy, and might save you time.
TIP
It is possible for the CMOS to be corrupted by a software or
hardware conflict and yet appear to be fine. If all else fails, reset
the CMOS and reinstall the CMOS setup (check the motherboard
manual for the jumper or disconnect the battery).
Check or Change the Floppy Disk Drive Cable
Cables wear out, work themselves loose, and are sometimes improperly
installed. Check out both the data cable and the power jack as possible causes
of the errant floppy disk drive before moving on to the controller.
Change the Floppy Disk Drive Controller
Today, most floppy drive controllers are built onto the motherboard. These are
quite reliable. In the event one does fail, however, you will usually have to
disable the on-board controller and add a separate controller on an expansion
card or replace the motherboard. It's actually less expensive to replace the
entire motherboard than to repair the floppy-related components.
Separate floppy disk drive controller cards are durable and highly resistant to
failure. Left alone, they generally cause no problems. However, cards that
have recently been handled, such as during a move or repairs to the
computer, can be suspect. They are extremely sensitive to shock and static
discharge.
In the event of a loose data cable or power plug, the power-on self test (POST)
will return "FDD Controller Failure" or "Drive Not Ready" errors. (For more
information about POST, refer to Chapter 6, "Motherboard and ROM BIOS.")
Verify all the connections and try again. If the connections are sound, try
removing and reseating the controller (being careful of electrostatic
discharge). If the same errors continue, replace the controller. Floppy disk
drives and controllers are inexpensive.
When replacing a floppy disk drive controller (see Figure 9.4), keep in mind
that most of these controllers on pre-Pentium machines (486 and older) are
bundled as part of a combination input/output (I/O) card. These cards include
some (often all) of the following: hard disk drive controllers, serial ports,
parallel ports, and joystick ports. If the new card contains any duplicate ports
(they already exist elsewhere on the computer), a potential for conflict exists.
Figure 9.4 I/O card with floppy disk controller
TIP
If you are installing a card that includes devices already installed
on the computer, be sure to disable duplicate devices on the card
before adding an I/O card. If not disabled, the duplicate
components will cause conflicts, and may keep the machine from
booting successfully, or force Microsoft Windows into safe mode. If
you have a new card with improved devices, disable or remove the
older items.
Replace the Floppy Disk Drive
When replacing floppy disk drives, be sure to throw away the old drive. Floppy
disk drives are inexpensive compared to other components in the computer.
Consider purchasing them in quantity to save money. It is a good idea to have
a spare floppy disk drive and I/O card available for testing purposes.
Lesson Summary
The following points summarize the main elements of this lesson:
The 3.5-inch floppy disk drive has become an industry standard.
Floppy disk drive technology has not changed much over the years.
Floppy disk drives fail more than any other part of a computer system.
Floppy drive parameters must be properly set in the system CMOS.
When a drive fails to read or write, check the drive (or, in the case of
floppies, the individual disk) for errors first, then the CMOS settings, and,
finally, the cable. If all of these fail, replace the drive.
3 4
Lesson 2: Hard Disk Drives
Hard disk drives are mass storage devices. Virtually all of today's PCs have at
least one hard disk drive. The first hard disk drives were small in capacity,
physically large, and expensive when compared to the cost of drives today.
They were about 4 inches tall, 5.25 inches wide, and 8 inches long, and they
weighed almost 10 pounds. In 1981, IBM introduced the XT computer with a
10-MB hard drive, and new owners wondered what they would do with all that
space. Today, a new hard disk drive can fit in your pocket and hold over 17 GB
of data. In this lesson, we examine hard disk drives, from the early versions to
today's minimonsters.
After this lesson, you will be able to
Explain the operation of a hard disk drive
Define the different types of hard disk drives, including their advantages
and disadvantages
Partition a hard disk drive
Troubleshoot hard disk drives
Estimated lesson time: 45 minutes
Physical Characteristics
The first form of PC mass storage was the magnetic tape drive, basically the
same as a music cassette recorder. Although tape proved a good medium for
storing large amounts of data, it had some significant limitations. The typical
cassette drive cartridge was easily damaged. Further, gaining access to the
data was slow due to the way data is organized on tape, as a long stream of 1s
and 0s, an arrangement known as "sequential." Tapes were hundreds of feet
long, and users often had to run the entire length of the tape to find the data
they were seeking. By providing random access (the ability to go directly to
any point on the data surface), floppy disks are a major improvement, but
they are too slow and too limited in capacity for modern applications.
The original concept behind the hard disk drive was to provide a storage
medium that held large amounts of data and allowed fast (random) access to
that data. Data on a hard drive can be accessed directly, without requiring the
user to start at the beginning and read everything until finding the data
sought.
The first IBM hard disk drives came out in the late 1970s and early 1980s and
were code-named "Winchester." The original design concept included two 30MB units in one enclosure: 30-30 (hence Winchester, after the well-known
rifle cartridge popular in western movies). The PC-XT was the first personal
computer to include a hard disk. They were called fixed disks because they
were not removable by the end user, like a floppy. (Old mainframe computers
had hard platters that were removable by a trained technician.) The
Winchester technology is the forerunner of all PC fixed disks.
Hard disk drives are composed of several platters, matched to a collection of
R/W heads and an actuator. Unlike floppy disk drives, a hard disk drive
assembly is housed in a sealed case, which prevents contamination from the
surrounding environment. Each case has a tiny aperture with an air filter. This
allows the air pressure to be equalized between the interior and the exterior of
the drive.
The platters are often made of an aluminum alloy and have a thin magneticmedia coating on both sides. After coating, the platters are polished and given
another thin coating of graphite for protection against mechanical damage
caused by physical contact between the data heads and the platter surface.
The R/W heads "float on a cushion of air" above the platters, which spin at
3500 to 12,000 revolutions per minute (rpm). The distance (flying height)
between the heads and the disk surface is less than the thickness of a
fingerprint.
Storing Data
As noted in previous chapters, data is stored using binary code. Within the
computer's memory, 1s and 0s are stored as electrical impulses. On magnetic
media, the 1s and 0s can be stored as either magnetic or nonmagnetic areas
on the drive surface. Although there are magnetized and nonmagnetized
positions on the hard disk drive, the 1s and 0s of the binary code are stored in
terms of flux reversals. These flux reversals are actually the transitions
between magnetized and nonmagnetized positions on the hard drive surface.
Early hard disk drives used a method of encoding called frequency modulation
(FM). FM technology is based on timing. To differentiate a 1 from a 0, it
measures the time the drive head spends in a magnetized state. For FM to
work, it requires every 1 or 0 to be preceded by a timing bit. The early FM
drives worked well, but all the extra bits added to the work and slowed the
process of data transfer. To improve efficiency and speed of the data transfer,
FM was replaced by an improved version that reduced the number of timing
bits required. This new technology was called modified frequency modulation
(MFM). MFM uses the preceding data bit to indicate whether the current bit is
a 1 or a 0, thus reducing the number of timing bits by more than 50 percent.
Another method used to place data on hard disk drives is run-length limited
(RLL) encoding. RLL replaces the timing bits with patterns of 1s and 0s that
represent longer patterns of 1s and 0s. Although this looks inefficient, the
elimination of the timing bits speeds overall performance.
TIP
Unless you're working with hard disk drives manufactured before
1989, it is not necessary to know which type of data encoding is
used.
Actuator Arms
The goal of a hard disk drive is to quickly and directly access data stored on a
flat surface. To do this, two different motions are required. As the disk spins,
the R/W heads move across the platter perpendicular to the motion of the
disk. The R/W heads are mounted on the ends of the actuator arms (much like
the arm of an old record player). A critical element in hard disk drive design is
the speed and accuracy of these actuator arms.
Early hard disk drives used a stepper motor to move the actuator arms in fixed
increments or steps. This early technology had several limitations:
The interface between the stepper motor and actuator arm required that
slippage be kept to a minimum. The greater the slippage, the greater the
error.
Time and physical deterioration of the components caused the positioning
of the arms to become less precise. This deterioration eventually caused
data transfer errors.
Heat affected the operation of the stepper motor negatively. The
contraction and expansion of the components caused positioning accuracy
errors. (Components expand as they get warmer and contract as they
cool. Even though these changes are very small, they make it difficult to
access data, written while the hard drive is cold, after the disk has
warmed up.)
The R/W heads need to be "parked" when not in use. Parking moves the
heads to an area of the disk that does not contain data. Leaving the
heads on an area with data can cause that data to be corrupted. Old hard
disk drives had to be parked with a command. Most drives today
automatically park the heads during spin-down.
NOTE
Older hard disk drives (pre-EIDE or SCSI-2) require that the heads
be parked before moving the computer. With these units it is
recommended that you use the appropriate command to park the
heads. The actual command can vary depending on the drive
manufacturer, but you can try typing park at an MS-DOS prompt.
Newer computers, including laptops, do not require that the drives
be parked.
Hard disk drives with stepping motor actuator arms have been replaced by
drives that employ a linear motor to move the actuator arms. These linear
voice coil motors use the same type of voice coil found in an audio
loudspeaker, hence the name. This principle uses a permanent magnet and a
coil on the actuator arm. By passing electrical current through the coil, it
generates a magnetic field that moves the actuator arm into the proper
position.
Voice coil hard disk drives offer several advantages:
The lack of mechanical interface between the motor and the actuator arm
provides consistent positioning accuracy.
When the drive is shut down (the power is removed from the coil), the
actuator arm, which is spring-loaded, moves back to its initial position,
thus eliminating the need to park the head. In a sense, these drives are
self-parking.
There is a drawback to this design: Because a voice coil motor can't accurately
predict the movement of the heads across the disk, one side of one platter is
used for navigational purposes, and so is unavailable for data storage. The
voice coil moves the R/W head into an approximate position. Then the R/W
heads on the reserved platter use the "map" to determine the head's true
position and make any necessary adjustments. This is why hard drive
specifications list an odd number of heads.
Head-to-Disk Interference
Head-to-disk interference (HDI) is a fancy term for head crash. These terms
describe the contact that sometimes occurs between the fragile surface of the
disk and the R/W head. This contact can cause considerable damage to both
the R/W head and the disk. Never move—or even pick up—a hard disk drive
until it is completely stopped; the momentum of the drive can cause a crash if
it is moved or dropped during operation.
Picking up a disconnected hard disk drive that is still spinning is not a good
idea either. The rotation force of the platters can wrench it out of your hands,
and the drive is not likely to survive the trip to the floor.
Geometry
Hard disk drives are composed of one or more disks or platters on which data
is stored. The geometry of a hard drive is the organization of data on these
platters. Geometry determines how and where data is stored on the surface of
each platter, and thus the maximum storage capacity of the drive. There are
five numerical values that describe geometry:
Heads
Cylinders
Sectors per track
Write precompensation
Landing zone
Write precompensation and landing zone are obsolete, but often seen on older
drives. Let's take a look at each of these components.
TIP
All hard disk drives have geometry factors that must be known by
the BIOS to read and write to the drive. Knowledge of the
geometry is required to install or reinstall a hard drive. New PCs
and drives often have technology that lets the BIOS get the
information directly from the drive. You still need to know the
figures, however, in case this technology fails.
Heads
The number of heads is relative to the total number of sides of all the platters
used to store data (see Figure 9.5). If a hard disk drive has four platters, it can
have up to eight heads. The maximum number of heads is limited by BIOS to
16.
Figure 9.5 Drive heads
Hard disk drives that control the actuator arms using voice coil motors reserve
a head or two for accuracy of the arm position. Therefore, it is not uncommon
for a hard disk drive to have an odd number of heads.
Some hard disk drive manufacturers use a technology called sector translation.
This allows some hard drives to have more than two heads per platter. It is
possible for a drive to have up to 12 heads but only one platter. Regardless of
the methods used to manufacture a hard drive, the maximum number of heads
a hard drive can contain is 16.
Cylinders
Data is stored in circular paths on the surface of each platter. Each path is
called a track. There are hundreds of tracks on the surface of each platter. A
set of tracks (all of the same diameter) through each platter is called a cylinder
(see Figure 9.6). The number of cylinders is a measurement of drive
geometry; the number of tracks is not a measurement of drive geometry.
BIOS limitations set the maximum number of cylinders at 1024.
Figure 9.6 Cylinders
Sectors per Track
A hard disk drive is cut (figuratively) into tens of thousands of small arcs, like
a pie. Each arc is called a sector and holds 512 bytes of data. A sector is shown
in Figure 9.7. The number of sectors is not important and is not part of the
geometry; the important value is the number of sectors per track. BIOS
limitations set the number of sectors per track at 63.
Figure 9.7 Sector
Write Precompensation
All sectors store the same number of bytes—512; however, the sectors toward
the outside of the platter are physically longer than those closer to the center.
Early drives experienced difficulty with the varying physical sizes of the
sectors. Therefore, a method of compensation was needed. The write
precompensation value defines the cylinder where write precompensation
begins.
NOTE
The write precompensation value is now obsolete, but is often seen
on older drives.
Landing Zone
A landing zone defines an unused cylinder as a "parking place" for the R/W
heads. This is found in older hard disk drives that use stepper motors. It is
important to park the heads on these drives to avoid accidental damage when
moving hard disk drives.
CHS Values
Cylinders, heads, and sectors per track (see Figure 9.8) are known collectively
as the CHS values. The capacity of any hard disk drive can be determined from
these three values.
Figure 9.8 Cylinders, heads, and sectors per track
The maximum CHS values are:
1024 cylinders
16 heads
63 sectors per track
512 bytes per sector
Therefore, the largest hard disk drive size recognized directly by the BIOS is
504 MB. Larger drive sizes can be attained by using either hardware or
software translation that manages access to the expanded capacity without
direct control by the system BIOS:
1024 × 16 × 63 × 512 bytes/sector = 528,482,304 bytes (528 million bytes
or 504 MB)
There are many hard disk drives that are larger than 504 MB. These drives
manage to exceed this limitation in one of two ways: Either they bypass the
system BIOS (by using one of their own) or they change the way the system
BIOS routines are read. (For a fuller discussion of this, refer to Chapter 10,
"Advanced Disk Drive Technology.")
Hard Disk Drive Types
The original PC design did not include hard disk drives. Hard disk drives were
reserved for large mainframe computers and remained highly proprietary in
design. Today, there are four types of hard drives, each with its own method of
installation.
ST506
The very first hard disk drives for personal computers used the ST-506/412
interface. It was developed by Seagate Technologies in 1980 and originally
appeared with the 5-MB ST-506 drive. The ST-506 was priced at $3,000 and
had a capacity of 5 MB. The ST-506/412 was the only hard drive available for
the IBM computer and was the first to be supported by the ROM BIOS chip on
the motherboard.
ESDI
The ESDI (Enhanced Small Device Interface) was introduced in 1983 by the
Maxtor Corporation. This technology moved many of the controller functions
directly onto the hard disk drive itself. This greatly improved data transfer
speeds. Some ESDI controllers even offered enhanced command sets, which
supported automatic sensing of the drive's geometry by the motherboard's
ROM BIOS. The installation of ESDI drives was almost identical to the
installation of ST-506 drives. Their high performance made them the darlings
in their day for power users and network servers, but the high cost of ESDI
drives and advances in other drive technologies spelled their doom. Today they
are obsolete.
IDE/EIDE
The IDE (Integrated Device Electronics) drive arrived on the scene in the early
1990s and incorporated the benefits of both its predecessors. IDE quickly
became the standard for computers. It supports the ST-506 standard command
set, and its limited controller functions build directly on the drive's logic board.
This results in a much less expensive design. Most new motherboards have the
IDE connections built in; thus, the chips are part of the board design.
Western Digital and Compaq developed the 40-pin IDE ISA (Industry Standard
Architecture) pinout specification. ANSI (American National Standards
Institute) standards committees accepted the standard as the Common Access
Method (CAM) Advanced Technology (AT). The official name for these drives is
now ATA/CAM (Advanced Technology Attachment/Common Access Method).
The terms IDE and ATA/CAM are interchangeable.
Enhanced IDE (EIDE) adds a number of improvements to the standard IDE
drives, including:
Increased data throughput.
Support of storage devices other than hard disk drives.
Up to four IDE devices instead of just two. This actually allows the BIOS
to support two controllers (each with two drives).
Support for hard disk drives larger than 528 MB.
NOTE
EIDE is the standard for most hard disks in today's PCs. A new
type of EIDE, Ultra DMA/66, doubles the base speed of existing
EIDE drives on motherboards that have a 66-MHz bus (hence the
name).
SCSI
SCSI (Small Computer System Interface, pronounced scuzzy) has been around
since the mid-1970s in one or more forms. It is the most robust of the hard
disk drive interfaces, and it is popular on network servers and highperformance workstations. Apple adopted SCSI as its expansion bus standard.
The original SCSI standard allowed up to seven peripheral devices to be daisy
chained (connected in a series) to one common bus through a single host
adapter connected to the computer bus. SCSI-2 upped that to 15, and some
adapters allow multiple chains for even more devices. (See Chapter 10,
"Advanced Disk Drive Technology," for more information on SCSI technology.)
The SCSI bus functions as a communications pathway between the computer
system bus and the SCSI device controller. That improves performance,
because the card takes over the low-level commands and frees the system bus
during operations that do not involve RAM. A SCSI adapter uses its own BIOS
and firmware to talk to its devices, then uses a software interface layer and
drivers to communicate with the operating system. There are two software
interface layers: ASPI (Advanced SCSI Programming Interface) and CAM. CAM
is now obsolete, and ASPI drivers come with Windows and other operating
systems. In most cases, you won't have to worry about loading the drivers
unless you are updating them or installing a new card that does not have
native drivers available to the operating system.
NOTE
Most SCSI cards can be configured to mimic the ST-506 hard disk
drive and talk directly to the PC BIOS. This lets you install a SCSI
hard drive without additional drivers. You will need the ASPI or
CAM software to get full use of advanced SCSI performance
features or to attach non-hard disk drive SCSI peripherals to the
system.
SCSI usually costs more than other hard disk drive interfaces, but is the only
one that allows both internal and external connections on the same adapter. It
also allows you to attach more types of devices than any other interface. A
single chain can include hard drives, CD-ROM and other optical drives,
scanners, and tape drives.
Installation and Setup
All boot devices must be configured outside the operating system (MS-DOS or
Windows 95, Windows 98, Windows Me, Windows NT, or Windows 2000)
regardless of the level of Plug and Play compatibility. (Devices such as disk
drives and CD-ROM drives that are used to boot must be configured at the
BIOS and hardware levels because they typically contain the operating system
and must run properly before the operating system can be started.)
Installation of a hard disk drive consists of five simple steps:
1. Physical installation and cabling
2. CMOS setup
3. Low-level formatting (if required)
4. Partitioning
5. Formatting
Cabling
Just as there are different types of drives, there are different cabling
requirements for each. Let's look at the three most common types.
ST-506
The ST-506 uses a 34-connector control cable (daisy chained for dual drives)
and a 20-connector data cable for each drive. The 34-wire control cable has a
twist in it for line 25 through 29 configuration (similar to the floppy disk drive
cable); this twist determines which hard disk drive is hard drive 0 and which is
hard drive 1. The drive at the end is drive 0.
CAUTION
Do not confuse or use a floppy drive cable to attach a hard drive to
a computer or vice versa; they are not interchangeable.
IDE/EIDE
IDE uses a simple 40-pin cable that plugs into the controller and into the drive
(see Figure 9.9). There are no twists. IDE controllers identify the two drives as
either master or slave. Drive makers use different methods to set up their
drives. The most common system uses jumpers. Setting these jumpers serves
the same function as the twist used with other drive cables: It identifies
whether the drive is a master or slave. Other drives use switches, and some
new drives use software to determine which is the dominant drive. Be sure to
check the manufacturers' specifications to properly set up the drive.
Ultra DMA/66
A special version of the 40-pin IDE cables is used for Ultra DMA/66. Be sure to
obtain and install it if you are working with one of these newer drives. It is
also 40-pin, but it has a blue connector on one end and a black one on the
other. All the other installation and cabling procedures are the same as for
traditional IDE devices.
Figure 9.9 IDE connections
TIP
When installing a new secondary IDE hard disk drive in a system,
be sure to set the new drive as slave and verify that the first drive
is set to master. The documentation supplied with the drive should
provide the necessary information. Often, this information is
printed on the label of the drive. Both drives must be properly
configured before the system is started. If the drives are not
properly jumpered, they won't work.
If you don't know the settings for the drive's jumpers (see Figure 9.10), try
calling the hard disk drive manufacturer (or look for its Web site on the
Internet).
Figure 9.10 Master and slave jumper settings
Setting the System CMOS for the Hard Drive
After a hard disk drive has been installed physically, the geometry of the drive
must be entered into the CMOS through the CMOS setup program before the
PC will recognize the new device. This information must be entered exactly as
specified by the manufacturer. Figure 9.11 shows hard disk drive configuration
information in a typical CMOS. Figure 9.12 shows a subscreen of the main
hard drive setup screen.
Figure 9.11 CMOS main screen
Originally, CMOS would allow for only two drives. Later versions allow up to
four drives, because most new PCs have two IDE channels, but you still have
to contend with IDE's limit of two devices per channel. Another thing to be
aware of is the number of non-hard drive devices (tape, CD-ROM, CD-R, and
so on) that may also be attached to a PC. When configuring a new system, it's
a good idea to ask customers if they plan on upgrading before making a final
decision on how to attach the drives. In most cases, the primary hard disk can
take the master position on the primary IDE channel, and the CD drive the
primary position on the second channel. For best performance, only hard
drives should be placed on the primary IDE channel, if possible.
The CHS, along with write precompensation and landing zone, determine how
the hard disk drive controller accesses the physical hard drive. The creators of
the first CMOS routines for the 286 AT believed that the five different
geometry numbers would be too complicated for the average user to configure,
so they established 15 preset combinations of hard drive geometries. These
preset combinations are called types. With types, the user simply enters a
hard drive type number into the CMOS.
Figure 9.12 Hard disk drive setup screen
This system worked well for a period of time, but with each new hard disk
drive that manufacturers designed, a new type also had to be created and
added to the list. BIOS makers continued to add new types until there were
more than 45 variations. To deal with this issue, setup routines now include a
user type. This allows manual entry of the geometry values, increasing both
the flexibility and complexity of hard drive installation.
CMOS setup is easy with IDE drives. Most CMOS chips today have a setting
known as IDE autodetection, which runs the IDENTIFY DRIVE command,
gathering and setting the proper geometry values. To use it, simply connect
the drive to the computer, turn it on, and run the CMOS. The IDENTIFY DRIVE
command instructs the drive to transmit a 512-byte block of data containing
the following information:
Manufacturer
Model and serial numbers
Firmware revision number
Buffer type indicating sector buffering or caching capabilities
Number of cylinders in the default translation mode
Number of heads in the default translation mode
Number of sectors per track in the default translation mode
Number of cylinders in the current translation mode
Number of heads in the current translation mode
Number of sectors per track in the current translation mode
IMPORTANT
Be sure to save your settings before you exit the setup program.
What happens if wrong data is entered into the CMOS? For example, what if a
1.2-GB hard disk drive is installed and the CMOS is set up to make it a 504MB hard drive? When you boot the computer, you will see a perfect 504-MB
hard drive. You will need to correct the entry to obtain proper use of the drive.
It should always make sure you go back and enter the correct information or it
could render the drive inaccessible by the system.
If the computer you are working on does not support autodetection, you must
be able to determine the geometry of a drive before you can install it.
There are many ways to determine the geometry of a hard disk drive:
Check the label. The geometry or type appears on the label of many hard
drives.
Check the documentation that came with the hard drive. All drives have a
model number that can be used to obtain the geometry parameters either
from the manufacturer or a third party. The hard drive manufacturers
usually reserve a section of their Web sites for providing configuration
data and the setup utilities available for download.
Contact the manufacturer. Many manufacturers have toll-free phone
numbers.
After a drive is installed, it must be assigned a drive name or letter that is
unique. There are several drive-naming conventions that help identify this
unique name. If only one hard disk drive is installed, it must be configured as
drive 0, or master. If a second drive is installed, it is recognized as hard drive
1, or slave. Many CMOS configurations use the terms C and D. Under all
versions of MS-DOS and Windows, hard drive 0 is recognized as C and hard
drive 1 is recognized as D.
As more drives are added to a system (including tape, CD-ROM, and network
drives), the names of existing drives might change. For example, installing a
portable drive such as an Iomega Zip drive can change a CD-ROM drive from
the D drive to the E drive. When the portable drive is removed, the CD-ROM
drive will once again be the D drive. Keep in mind the difference between
logical and physical drives. A physical drive is the hardware—it can be divided
into two or more logical drives. (See the "Partitioning" section later in this
lesson.) Drives on a network server are also logical drives. Write down the
configuration and keep track as changes in the system are made. The only
drive letters that are fixed are the A and B drives, which are always the floppy
disk drives, and the C drive, the boot drive where the operating system
resides.
NOTE
Confusion in drive letters can also confuse the operating system,
making it hard or impossible for it to locate drivers. In such cases,
you might need to reinstall the drivers before the system can
make use of the affected hardware, and a Windows 95, Windows
98, Windows Me, or Windows 2000 machine might automatically
start in safe mode. Check the Device manager by double-clicking
the System icon in the Control Panel after the PC is operational,
and look for duplicate hardware items or items denoted by flags
noting missing or inoperable conditions.
Low-Level Formatting
Low-level formatting means creating all the sectors, tracks, cylinders, and
head information on the drive, and this is the third step in installing hard disk
drives; generally, it applies only to older drives. Low-level formatting by the
end user has virtually been eliminated with today's drives (it's done at the
factory).
A low-level format performs three simultaneous functions:
It creates and organizes the sectors, making them ready to accept data.
It sets the proper interleave (records the sector header, trailer
information, and intersector and intertrack gaps).
It establishes the boot sector.
Every hard disk drive arrives from the factory with bad spots on the platters.
Data cannot be written to these areas. As the sectors are being created, the
low-level format attempts to skip over these bad spots. Sometimes, it is
impossible to skip over a spot, so the sector is marked as "bad" in the ID field.
CAUTION
Low-level formatting is not required on IDE and Ultra DMA drives.
Performing a low-level format on these devices might render the
drives unusable. SCSI drives are low-level formatted using a utility
that is built into the SCSI adapter card's firmware. Format a lowlevel drive only if it is absolutely necessary (for example, if a virus
has contaminated the boot sector and that is the only remedy) and
if you are sure you know and can follow the proper procedure.
Remember, as soon as you issue the FORMAT command, all data
on the drive will be lost.
IDE drives use a special type of low-level formatting called embedded servo.
This type of low-level formatting can be done by the manufacturer only, or
with a special utility provided by the manufacturer. When installing an IDE
drive, go straight to the partitioning step after the CMOS is set up. To continue
with hard disk drive installation for MS-DOS and Windows 3.x, Windows 95,
Windows 98, and Windows Me versions, you will need a bootable floppy disk
containing several programs that are required to prepare the new drive. (For
Windows NT and 2000, there are options that will allow you to prepare a drive
from the bootable CD-ROM.)
To create a bootable floppy disk, a computer is required that has an installed
working hard disk drive, or floppy disk drive, and a compatible operating
system. Be sure to use the same operating system on the floppy disk as the
one you'll use for the new drive.
Insert a floppy disk into the A drive and type:
format a: /s to
This will copy system files to the disk, making it a bootable disk.
The next step is to copy the necessary files from the MS-DOS directory to the
floppy disk. The default location for these files is the C:\DOS directory for MSDOS and the C:\Windows\Command directory for Windows 95, Windows 98,
and Windows Me. Copy these files:
FORMAT.COM (or FORMAT.EXE)
FDISK.COM
This bootable disk can be used for partitioning and high-level formatting as
discussed in the following sections.
Partitioning
Partitions are logical divisions of a hard drive. A computer might have only one
physical hard drive (called hard drive 0), but it can have anywhere from 1 to
24 logical drives, identified as C to Z.
Partitions exist for two reasons:
To divide the disk into several drive letters to make it easier to organize
data files. Some users separate data, programs, and operating system
files onto different drives.
To accommodate more than one operating system.
When MS-DOS was first designed to use hard disk drives, the largest hard
drive that could be used was 32 MB (because of the way MS-DOS stored files
on the hard drive). Partitioning was included in MS-DOS 3.3. This allowed for
the development of larger physical hard drives by creating multiple logical
drives of up to 32 MB each. Starting with MS-DOS 4.0, the partition size was
increased to 512 MB. Beginning with MS-DOS 5.0, the partitions could be as
large as 2 GB. Windows 98, Windows Me, and Windows 2000 support much
larger drive sizes, and many new disks exceed 20 GB.
NOTE
Some hard disk drives that exceed 4 GB might not work with an
older computer, BIOS, or operating system. They will physically
function, but the whole drive cannot be accessed—disk access will
be limited to the largest size that can be recognized by that
system.
Primary and Extended Partitions
There are two types of partitions: primary and extended. The primary partition
is the location where the boot information for the operating system is stored.
To boot from a hard disk drive, the drive must have a primary partition.
Primary partitions are for storage of the boot sector, which tells the computer
where to find the operating system. The primary partition is always identified
as drive C.
The extended partition is for a hard disk drive, or part of a hard disk drive,
that does not have an operating system. The extended partition is not
associated with a physical drive letter. Instead, the extended partition is
further divided into logical drives starting with D and progressing until drive
letter Z is created. (Remember: A and B are reserved for floppy disk drives.)
Newer operating systems can use all of the drive as a single primary partition.
The logical drive concept was invented to allow older versions of MS-DOS and
Windows to make use of drives that exceeded their maximum drive size.
How to Partition
The fdisk utility is used to partition a drive under DOS, Windows 3.x, Windows
9x, and Windows Me. After the drive is installed and the CMOS is updated, run
fdisk to partition the drive(s). Figure 9.13 shows the fdisk startup screen.
Windows NT and 2000 have options during setup that are offered to partition a
drive during installation of a new operating system. Follow the prompts for
these environments as they appear.
You also have the option of using a third-party utility to partition the hard
drive, which often provides more sophisticated and graphical methods for
partitioning a drive, thereby simplifying the partition process.
Figure 9.13 The fdisk startup screen
The function of lines 1, 3, and 4 is clear. Line 2 sets the active partition. The
active partition is the partition where the BIOS will look for an operating
system when the computer is booted.
Don't confuse the primary partition with the active partition. On a computer
with a single operating system, the primary and active partitions are usually
the same. A computer with dual-boot capability might have separate partitions
for each operating system. In that case, the active and primary partitions
might not be the same.
The primary partition is where MS-DOS (or the Windows boot information) is
stored on the hard disk drive, and the active partition is where the operating
system is stored on the hard drive. (If MS-DOS is the only operating system,
the primary partition and active partition are the same.) Other operating
systems—Windows NT, Windows 2000, and LINUX, for instance—can exist on
an extended partition.
Advanced operating systems can create a special partition called a boot
partition. When the computer boots, a menu prompts the user to pick which
operating system to use. The boot manager then sets the chosen partition as
active, which starts the operating system located in that partition. As with
partitioning software, you can also purchase third-party boot managers for
systems that do not provide an option for booting to multiple operating
systems.
NOTE
MS-DOS has a limitation not shared by any other operating
system: it must be placed on the primary partition, and that
partition must always be named C. LINUX, UNIX, and Windows NT
and 2000 can boot from another drive letter, as well as from the C
drive.
High-Level Formatting
The high-level format is simply called "format" (the program used to perform a
high-level format is called FORMAT.COM). This is the same format command
used to prepare floppy disk drives. The high-level format performs two major
functions:
It creates and configures the file allocation tables (FATs).
It creates the root directory, which is the foundation on which files and
subdirectories are built.
File Allocation Tables
The base storage unit for drives is a sector. Each sector can store between 1
byte and 512 bytes of data. Any file less than 512 bytes is stored in a single
sector, and only one file can be assigned a sector. Therefore, any part of a
sector left unfilled is wasted. When files are stored in more than one sector (if
they are greater than 512 bytes), MS-DOS needs a way to keep track of each
location and the order in which data is stored. MS-DOS also needs to know
which sectors are full and which sectors are available for data, so it uses the
FAT to keep track of this information.
There are several versions of FAT, as well as other disk allocation schemes
used by operating systems like Windows NT, 2000, and various versions of
LINUX and UNIX. We will consider these versions in later chapters as we
examine operating system issues. For our current discussion we will focus on
the basics of FAT to show how data is stored on a disk drive. All operating
systems must use some well-defined method of writing, addressing, and
reading data in a way that is compatible with the drive technology being used.
In some cases, as with SCSI drives (see Chapter 10, "Advanced Disk Drive
Technology"), the hardware may actually "pretend" to use a system like FAT
but translate its own addressing scheme into FAT when it communicates with
the operating system.
The FAT is simply an index that keeps track of which part of the file is stored
in which sector. Each partition (or floppy disk) has two FATs stored near the
beginning of the partition. These FATs are called FAT #1 and FAT #2. They are
identical. Each FAT can be looked at as a two-column spreadsheet.
Left Column
Right Column
Gives each sector a number (in hex) from
0000 to FFFF (65,536 sectors). The left
side contains 16 bits (4 hex characters =
16 bits). This FAT is called a 16-bit FAT.
Floppy disk drives use 12-bit FATs because
they store substantially less data.
Contains information on the
status of the sector. During
formatting, any bad sectors
are marked with a status
code of FFF7 and good
sectors are marked 0000.
Sectors and Clusters
As mentioned, the CHS values limit the maximum size of a hard disk drive to
504 MB under the older PC operating systems. The 16-bit FAT can address
64,000 (2l6) locations. Therefore, the size of a hard drive partition should be
limited to 64,000 × 512 bytes per sector or 32 MB. With this limitation, you
might ask, how are larger hard drives possible?
There are two solutions to this problem. The first method, used with earlier
drives (under 100 MB), was to use fdisk to break the drive up into multiple
partitions, each less than 32 MB.
The second method is called clustering. Clustering means combining a set of
contiguous sectors and treating them as a single unit in the FAT. The number
of sectors in each cluster is determined by the size of the partition. There can
never be more than 64,000 clusters. To determine the number of sectors in a
partition, divide the number of bytes in the partition by 512 (bytes per sector).
Then divide the number of sectors by 64,000 (maximum allowable clusters).
The following table provides an estimate of sectors per cluster.
Partition (in
MB)
Total Bytes
Total
Sectors
Sectors per
Cluster
Bytes per
Cluster
32
33,554,432
65,536
1
524
64
67,108,864
131,072
2
1,049
128
134,217,728
262,144
4
2,097
256
268,435,456
524,288
8
4,194
512
536,870,912
1,048,576 16
8,389
1,000
1,048,576,000 2,048,000 32
16,384
2,000
2,097,152,000 4,096,000 64
32,768
4,000
4,194,304,000 8,192,000 128
65,536
NOTE
Remember, for this table, a sector is not the basic unit of storage—
it is now the cluster.
How the File Allocation Table Works
When a file is saved:
1. MS-DOS starts at the beginning of the FAT and looks for the first space
marked "open for use" (0000). It begins to write to that cluster.
2. If the entire file can be saved within that one cluster, the code FFFF (last
cluster) is placed in the cluster's status field and the filename is added to
the directory.
3. The cluster number is placed with the filename.
4. If the file takes more than one cluster, MS-DOS searches for the next
open cluster and places the number of the next cluster in the status field.
MS-DOS continues filling and adding clusters until the entire file is saved.
5. The last cluster then receives the end-of-file code (FFFF).
FAT32
Windows 95 (OSR2—the final version of Windows 95, available only on new
machines, also called version C), Windows 98, and Windows Me support the
new FAT32 file system. FAT32 can create partitions of up to 2 terabytes (TB;
equivalent to 2 trillion bytes) in size (much larger than the 2-GB limit of
FAT16) and uses smaller clusters than FAT16. This results in a more efficient
use of space on a large hard disk.
When deciding whether to use FAT32, take the following into consideration:
Don't use advanced file allocations systems (FAT32, NTFS) on any
partition shared by other operating systems unless they can specifically
support it.
MS-DOS, Windows 3.x, the original release of Windows 95, and Windows
NT clients can read FAT32 partitions shared across a network.
If you dual boot between Windows 98 and another operating system
(such as Windows NT 4.x), the drive C partition cannot be FAT32.
You cannot compress FAT32 partitions.
Windows 98 MS-DOS mode fully supports FAT32, so you can run most
MS-DOS-mode games and applications from FAT32 partitions.
Some older applications written to FAT16 specification might not display
disk space larger than 2 GB.
Do not use any utilities that do not support FAT32. This could result in
data loss and might corrupt the file system on the hard drive.
Fragmentation
Fragmentation is the scattering of parts of the same disk file over different
areas of the disk. During PC use, files are opened and then saved back to disk.
As mentioned earlier, the file is often stored in several small sections.
Fragmentation is caused by the following:
1. As a file is written to sectors (clusters), it is placed in the first available
location.
2. The continual addition and deletion of files begins to leave open clusters.
3. These open clusters are filled by the first part of the next file to be saved.
4. Soon, files become fragmented, or scattered, all over the drive.
This is an acceptable way to operate and causes no problems for the computer
itself. However, excessive fragmentation slows down the hard disk drive
because it has to access two or more areas to retrieve a file. It is possible for a
single file to be fragmented into hundreds of pieces, forcing the R/W heads to
travel all over the hard disk drive.
Most operating systems have either native or third-party applications that will
defragment a drive. These should be used on a regular basis to improve
performance and save wear and tear on the drive.
The elimination of fragmentation improves the speed of the hard disk drive
dramatically. Running a program to eliminate fragmentation is called
defragmenting a drive. The slang term "defrag" is often used. MS-DOS
installations include a defragmentation program called DEFRAG. Windows 95,
Windows 98, and Windows Me include a defragmentation program, which can
be accessed by clicking Start, selecting Programs, then Accessories, then
System Tools, and then Disk Defragmenter.
NOTE
DEFRAG cannot rewrite or move systems and hidden files. These
files might be program files that are copy protected and must not
be moved after the program is installed. System files such as the
MS-DOS core program must occupy a particular position on the
disk.
CAUTION
Never run a defragmentation program designed for MS-DOS or
Windows 3.x on a Windows 95 or 98 system. The program might
not understand the Windows 95 and 98 long filenames, and data
might be lost.
Disk Compression
Disk compression is offered as part of the Microsoft Plus add-on product for
Windows 95, but is included in Windows 98 as the DriveSpace 3 program
(Windows Me includes DriveSpace 3, but does not support compression). It
works by creating a single large file (called a compressed volume file, or CVF)
that acts like a virtual disk drive (with its own drive letter). Files you write to
the CVF will become records within the one large file. This process is normally
transparent to the user.
NOTE
Keep in mind that you cannot use DriveSpace 3 with partitions
that use the FAT32 file system. If you wish to compress a drive
under Windows 98, use the FAT16 file system when installing the
drive.
Compression saves space in two ways:
It eliminates the wasted cluster space used by separate disk files.
It replaces sequences of identical values or characters in the file data with
a special reference that represents the actual data, but occupies less disk
space than the data itself would.
When the data is retrieved from the file, the real values are extracted
from the special references. The result can be a dramatic reduction in the
disk space occupied by files, especially with uncompressed graphics files
and word processing documents.
Using compression introduces some risk because an error in the CVF can make
data inaccessible. It is safest not to use a compressed file for critical data, and
some older programs (particularly games) might not work with compression.
With DriveSpace 3 you can use the Troubleshooter to identify and fix
problems.
Compression is less necessary today because of the advent of large hard disk
drives and the availability of the FAT32 file system with its smaller cluster
sizes.
Maintaining a Disk Drive
Being prepared for a potential failure before a hard disk drive fails to work
properly can save lost data and time. How fully you should prepare depends on
the answers to two questions:
Can you afford to lose the data in question?
How much time do you have to start over?
With this in mind, to minimize the impact of a hard disk drive failure:
Perform comprehensive, regularly scheduled backups.
Save a copy of the boot sector and partition table information.
You should have the following tools on hand to perform hard disk repairs:
A list of the hard disk drive's parameters and the correct CMOS settings
required.
A bootable floppy disk with the fdisk, format, chkdsk, and mscdex (if using
a CD-ROM) command files. Adding EDIT or another text editor is handy
for tweaking the CONFIG.SYS and AUTOEXEC.BAT files. Windows users
can create a startup disk with these files by clicking Start, selecting
Settings, then Control Panel, double-clicking Add/Remove Programs, and
clicking the Startup Disk tab. Third-party utilities also provide the ability
to create these "emergency" disks.
Drivers needed to get the operating system running with any primary
expansion cards (drive controllers, SCSI card, display adapter, and so on).
Good cables for the kinds of drives you might have to repair.
Chkdsk or other hard disk inspection programs that are part of the
operating system on the drive in question. Be sure to use the right
version.
A number of third-party programs are also available for use with older
hardware and operating systems. These programs are available at most
computer software stores.
CAUTION
When using any third-party programs to troubleshoot or repair a
drive, be sure they are certified for the hard disk drive and
operating system in question. Use uncertified third-party programs
only when such a step is the last resort before discarding the
drive. Even then, be aware that the program may cause problems
of its own. Keep the software up to date; changes in the operating
system or bugs found in the utility can render the product more of
a problem than a cure. If possible, back up any critical data before
using the software.
Abort, Retry, Fail or Abort, Retry, Fail, Ignore Errors
The most common drive errors begin with "Abort, Retry, Fail," or "Abort,
Retry, Fail, Ignore." When you see any of the following errors, you have a
drive problem:
Sector not found reading drive C:
Abort, Retry, Fail?
Data error reading drive C:
Abort, Retry, Fail, Ignore?
Read fault reading drive C:
Abort, Retry, Fail, Ignore?
Invalid media type reading drive C:
Abort, Retry, Fail?
These errors are the easiest to fix and can usually be attributed to a bad sector
on the drive. When this happens, try the following.
ScanDisk
MS-DOS, Windows 3.x, Windows 95, Windows 98, and Windows Me contain
versions of the ScanDisk program. ScanDisk performs a battery of tests on a
hard disk, including searching for invalid filenames, invalid file dates and
times, bad sectors, and invalid compression structures. In the file system,
ScanDisk looks for lost clusters, invalid clusters, and cross-linked clusters.
Regular use of ScanDisk can help prevent problems as well as fix them.
Windows 95-, Windows 98-, and Windows Me-based computers will
automatically run ScanDisk any time the operating system is improperly shut
down—that is, when the power is turned off before the system is allowed to
complete its shutdown procedures.
Verify the Media
Most SCSI drives have a program built into the controller that will verify the
hard disk drive and make repairs if a sector has become unusable or unstable.
Boot the PC and watch for a prompt to enter the SCSI BIOS setup (usually
Ctrl+A). Then choose Disk Utilities and the option to verify or inspect the
drive. Do not select the low-level format option. After the program is finished,
reboot the computer and see if the problem is resolved. If the disk fails
verification, it might need to undergo low-level formatting or be replaced.
CMOS Errors
At times, the system CMOS becomes unstable. This can result in the following
error messages:
CMOS configuration mismatch
No boot device available
Drive not found
Missing operating system
Checking the CMOS is quick and easy. It is a good idea to always have a
backup of the CMOS data on paper.
NOTE
After booting up, if you receive the message "Strike F1 key to
continue," this indicates that your system configuration is invalid
and you will need to check the CMOS settings.
Connectivity Errors
Connectivity problems (when something is not connected or plugged in)
usually appear when you boot up a computer. Look for the following messages:
HDD Controller failure
No boot device available
Drive not found
Connectivity errors are overcome by inspecting the entire connection system
(including power). You might want to try removing and reseating the controller
if you get an HDD controller failure.
TIP
As a computer technician, you should keep an extra controller and
cables around. Often, substituting a good cable or controller is the
quickest way to solve a hard disk drive problem.
Lost Boot and Partition Information
It is possible for a drive to lose partition information. Look for these errors:
Invalid partition table
Corrupt boot sector
Non-system disk or disk error
Boot and partition information is stored on sectors and can fail. If the partition
table or boot sector is corrupted, the best solution is to restore the data on the
drive from a backup copy after repartitioning the drive and reloading the
operating system.
Lesson Summary
The following points summarize the main elements of this lesson:
The maximum storage capacity of a hard disk drive is determined by its
geometry.
CHS values define the geometry of a hard disk drive.
The largest hard disk drive recognized by the BIOS will vary with the age
of the system.
Proper CMOS settings are required for hard disk drives.
There are two types of partitions: primary and extended.
A cluster is the basic unit of storage.
The fdisk program is used to partition drives under MS-DOS.
Microsoft ScanDisk is a useful tool for diagnosing and repairing many disk
problems.
The proper drive information must be held in CMOS for proper drive
operation.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Floppy Disk Drives
The first disk drives were floppy disk drives. The technology of floppy
disks has changed little in the past decade.
Floppy disk drives are designated as A or B. The drive letter designation is
determined by the location of the drive on the cable.
Floppy disk drives fail more than any other part of a computer system.
Hard Disk Drives
The three major steps in installing a hard disk drive are to partition the
drive, set the CMOS settings, and format the drive.
Fdisk is used to partition hard disk drives. A computer technician should
be familiar with the use of fdisk and partitioning.
The geometry of a hard disk drive (CHS values) determines its storage
capacity.
There are two types of partitions: primary and extended. The operating
system must be on the primary partition.
The active partition is where the operating system is stored. The active
partition is usually (but not always) the primary partition.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. What is the purpose of an IDE drive?
2. How many drives can be connected to a single IDE connector?
3. What is the best method of determining the number of drives available on
a computer?
4. What three things should be checked when a floppy disk drive fails?
5. What is the best way to ensure long life from a floppy disk drive?
6. When you purchase a new floppy disk drive controller, what can you
expect to receive with it?
7. Other than physical size, what are the only differences between a 5.25inch floppy disk drive and a 3.5-inch floppy disk drive?
8. What type of cable is used to connect a floppy disk drive to the external
data bus?
9. What is the proper way to install a floppy disk drive cable?
10. To which pin must the number 1 wire of the floppy disk drive cable be
connected?
11. You've received the following error message: "General failure reading
Drive A:". What is the most likely problem?
12. Are floppy disk controllers sensitive to ESD?
13. You receive an error message that ends with "Abort, Retry, Fail?". What is
the most likely cause of the error?
14. Why is a voice coil actuator arm better than a stepper motor actuator
arm?
15. Define hard disk drive geometry.
16. What is the best way to determine the geometry of an unknown drive?
17. Describe HDI.
18. BIOS limits the number of heads to _____________.
19. BIOS limits the number of cylinders to _____________.
20. How many bytes of data does a sector hold?
21. What is the maximum number of sectors per track?
22. What does CHS stand for?
23. What type of drive is standard on today's personal computer?
24. Name the characteristics of the three different hard disk drive types.
25. What is a partition? What are the two types of partitions?
26. Define a cluster.
27. What is the FAT and how does it work?
28. What is fragmentation?
29. How can you minimize the impact of a hard disk drive failure?
30. What is the function of ScanDisk?
Answers
3 4
Chapter 10
Advanced Disk Drive Technology
About This Chapter
This chapter picks up where the previous chapter left off; we continue our look
at disk drives, moving on to more advanced technologies. The lessons in this
chapter cover CD-ROM/DVD drives, newer and larger hard disk drives, and
Small Computer System Interface (SCSI) drives. In the final lesson, we also
explain the basics of the SCSI interface.
Before You Begin
Before starting this chapter, you should review Chapter 9, "Basic Disk Drives."
3 4
Lesson 1: CD-ROM and DVD Drives
Both CD-ROM (compact disc read-only memory) and DVD (digital video disc)
drives are based on technology taken directly from the multimedia world, and
both have become standard equipment for computers. This lesson covers the
basics of installing and using CD-ROM drives.
After this lesson, you will be able to
Define the advantages of using CD-ROMs
Explain the differences between CD-ROMs and DVDs
Install and operate both CD-ROM and DVD drives
Estimated lesson time: 30 minutes
Advantages of CD-ROM and DVD Drives
If a hard disk drive holds more information than a floppy disk drive, accesses
the information faster, and reads and writes information, then why do we need
CD-ROM drives? The answer is simple: A compact disc (CD) can hold large
amounts (650 MB) of removable data and can be mass-produced at a very low
cost.
Both CD-ROM and DVD technologies make use of high-capacity optic media in
the form of a silvery platter that holds digital data that is decoded by striking it
with a laser beam. To the casual observer, the discs used by both are the
same. In fact, most new DVD technology employs a shorter wavelength laser
to read the data than the type found in CD-ROM drives. That lets
manufacturers cram more data (like an entire movie, including the
soundtrack) on a single platter.
Many new PCs come with a DVD drive that can also read CD-ROMs. To play
movies effectively, they must also have decoding hardware, either on the drive
or on a companion card (sometimes part of the display adapter). Without the
performance boost the additional hardware provides, the playback will be
choppy with lost frames and erratic sound.
The CD has become the medium of choice for software distribution by
manufacturers. Because there are many PCs with only CD-ROM capability, and
several lingering questions about standards for DVD formats, it is expected
that CD-ROM will be a standard distribution method for the foreseeable future.
One CD can store an entire software package. While early versions of the
Microsoft Office Suite were supplied on 32 floppy disks, today the entire
program suite and its manuals are stored on a single CD. It is also much faster
to install a CD. The user simply starts it up, enters any required information,
and comes back later; it is no longer necessary to feed disk after disk into the
computer. When they were introduced, CDs held large databases such as
encyclopedias. Today, they are used for every possible type of data, from
national phone directories and software libraries to collections of clip art,
music, and games. The following table lists the advantages of storing data on a
CD.
Advantage
Large
storage
capacity
Description
Up to 650 MB of data fit on a single 5-inch disc. (Smaller
compared
than the original 5.25-inch floppy disk, a CD holds almost
to floppy2000 times as much information.)
type media
Portability
The CD is a portable medium.
Data
cannot be
changed
A CD is read-only, which prevents accidental erasure of
programs or files.
Sturdiness
More durable than the standard 5.25-inch or 3.5-inch disks,
CDs are not magnetic media and thus are not subject to the
same dangers posed by proximity to electrical sources or
magnets (although you need to handle them carefully to
avoid finger prints and scratches).
CD-ROMs are audio-capable, allowing special compression of
Special
audio, image, and video data. They can be used to play
capabilities standard audio CDs and have the capacity to store and
record video data.
Development of the CD
The development of the computer CD roughly paralleled the audio (music) CD:
In 1979, the CD, as a storage medium, was introduced in the audio
industry.
In 1985, the CD came to the computer industry. Development was slow
because the hardware was too expensive for most manufacturers and
users.
In 1991, the CD-ROM/XA standard was enhanced, and multimedia
requirements for hardware were specified.
In 1993, high-quality video playback came to the computer.
Today, the price of CD-ROM drives continues to drop, while their speed
climbs. Almost all new computers include an internal CD-ROM drive as
standard equipment. Most software packages are shipped in CD-ROM
versions (3.5-inch floppy disk versions are available but usually only by
special order, and often they do not contain all the extras of the CD
version).
About CD-ROM Standards
The CD-ROM world makes use of several standards. These are usually referred
to by the color of the cover of the volume issued by the ISO (International
Organization for Standardization) committee—for example, the White Book,
Yellow Book, and so on. We discuss ISO formats in more detail later in this
lesson.
CD-ROM Technology
CD-ROMs store data as a series of 1s and 0s, just like a floppy disk or a hard
disk drive. However, instead of using magnetic energy to read and write data,
CD readers and writers use laser energy. There are two major advantages to
using lasers:
There is no physical contact between the surface of the CD and the
reading device.
The diameter of the laser beam is so small that storage tracks can be
written very close together, allowing more data to be stored in a smaller
space.
Hard Disk Drives vs. CD-ROMs
With the cost of hard disk drives falling and the amount of available data
storage rising, the hard drive is still king of the storage media. Optical data
storage devices hold their place as removable media and as the media of
choice for archival data storage.
A CD platter is composed of a reflective layer of aluminum applied to a
synthetic base that is composed of polymers. A layer of transparent
polycarbonate covers the aluminum. A protective coating of lacquer is applied
to the surface to protect it from dust, dirt, and scratches.
NOTE
CD-recordable (CD-R) discs use materials other than aluminum.
They often have a yellow or green cast on the data side. Not all
CD-ROM readers are able to read these discs—some older readers
based on Integrated Device Electronics (IDE) are incompatible with
CD-R technology.
Data is written by creating pits and lands on the CD's surface. A pit is a
depression on the surface, and a land is the height of the original surface. The
transition from a land to a pit or a pit to a land represents a binary character
of 1. Lands and pits represent binary 0. The reading of data is based on timing
—the speed at which the CD is rotating—and the reflection of light. If no data
is on the disk, the reflectivity will not change and the CD will read a series of
binary 0s. There are approximately 4 to 5 million pits per CD, arranged in a
single outward-running spiral (track) approximately 3.75 miles (6 kilometers)
long. The distance between each element is 1.6 thousandths of a millimeter.
DVD: A Super CD-ROM Alternative
As already noted, DVD drives are becoming more popular and are usually
backward compatible with CD-ROMs. They come in several varieties, both
internal and external. The most popular in the PC market is the Enhanced IDE
(EIDE) internal style. While this product looks much like a CD-ROM drive, and
installs virtually the same way, you need to be at least somewhat familiar with
the different standards that exist in the DVD arena.
DVD Formats
DVD-ROM
This a data read-only format, much like a CD-ROM disc, that can be
engineered to hold up to 17 GB of digital information by encoding data on both
sides of the disc.
DVD Video
A 4.7-GB disc format designed to distribute movies, these platters hold up to
135 minutes of high-quality video. In addition, this format can store eight
digital soundtracks (AC3 and/or Digital Dolby) and subtitles. Many movies on
DVD also come with commentary, interviews with the artists, theatrical
trailers, and even alternate versions of endings or scenes deleted from the
version shown in theaters.
DVD-R
The R stands for recordable. This type of DVD media is similar in use to the
single record type of CD-R platter and contains up to 3.95 GB of data per side.
Like CD-R, you can only record to the disc once.
DVD RAM/RW
There are several Read/Write (RW) DVD drives on the market. Because of the
incompatibilities among vendors, this DVD technology has been very slow in
gaining acceptance. Keep in mind that the "Write" aspect is not unlimited and
that the actual number of changes varies based on the technology.
Connecting CD-ROM and DVD Drives
In most cases, there is no difference in attaching a CD-ROM or DVD drive. The
speed rates described later (like 4X) are based on the speed of the original CDROM drives and are used to gauge the relative speed of both CD-ROM and DVD
products. Depending on the features and design, you may have to install an
add-on decoder card with a DVD product to improve performance when playing
movies. Both types of drives are peripheral devices and must be connected to
the bus of the computer through a controller. There are several ways to install
them.
Adapter Boards
Some manufacturers provide a proprietary adapter board made specifically for
their product. These boards are supplied with the drive and are not usually
interchangeable. Early CD-ROM drives used either SCSI or a special version of
a parallel port. Most modern CD-ROM devices are either EIDE or SCSI. Many
DVD drives come with a decoder board to improve movie and audio playback.
When installing a drive with such a card, check if the system's display adapter
can handle the decoding. If so, you may be able to streamline the process by
using the existing card.
Sound Cards with CD-ROM Interface
Many add-on sound cards have built-in CD-ROM controllers. Most sound cards
come with a 15-pin female connector known as the MIDI (Musical Instrument
Digital Interface) connector. Some of the newer cards come with a SCSI
interface. Sound cards with the built-in controller interface were very useful
for earlier computers that did not have a controller available on the
motherboard. Because today's motherboards have the ability to connect four
IDE devices, a sound card with a controller is generally not required.
TIP
If you purchase a sound card with a controller and you already
have a CD-ROM drive installed, be sure to disable the controller on
the sound card. This will prevent IRQ (interrupt request) and other
potential conflicts.
SCSI Host Adapter
The SCSI interface, the most advanced CD-ROM interface, often operates at
higher data transfer rates than other interfaces. A single card can handle both
internal and external drives, including CD-ROM and other optical devices. You
can find a more detailed discussion of SCSI drives in Lesson 3, "SCSI Drives."
A SCSI CD-ROM drive can be installed in any SCSI chain. You can purchase
SCSI adapters that connect directly to a parallel port on the computer.
EIDE
Most computers have primary and secondary EIDE connectors as part of the
motherboard and BIOS (basic input/output system) setup. It is becoming
commonplace to install CD-ROM drives on the secondary controller.
Audio Capability
Any CD-ROM drive that meets the Yellow Book standards (created by the audio
industry for sound and adopted by the computer industry) has the ability to
play back audio. Most CD-ROM drives contain the circuitry and chips to convert
digital audio data into sound data. Most drives and sound cards also have a
headphone jack, as well as audio jacks to connect to a stereo system. The only
requirement is that the drive support the ISO 9660 standard, also known as
the High Sierra specification, for the file system. The ISO 9660 format is a
standard for writing data to a CD-ROM for use in a cross-platform
environment. This standard is compatible with MS-DOS, Microsoft Windows,
UNIX, Macintosh, and other operating systems.
Access Time
When purchasing or recommending a CD-ROM drive, you need to consider two
values. The first is data transfer rate. The longtime standard for transfer rate
has been 150 KB per second, and this is the basis for measuring CD-ROM
drives today. A 2X CD-ROM drive operates at 300 KB per second, a 4X at 600
KB per second, and so on. A typical CD-ROM drive today will operate at 24X,
32X (4.8 MB per second), or faster. A hard disk drive typically operates
between 800 KB and 1.8 MB per second.
The second value you should look at is the drive's mean access time, the time
it takes the head to move over half the tracks. Typical access time is 200 to
400 milliseconds (ms). Today's CD-ROM drives can have faster data transfer
speeds than many hard drives, but their mean access time is 20 or so times
slower. This means that, although a CD-ROM drive will outperform the hard
disk drive for copying or loading a large chunk of contiguous data, the hard
drive will perform better on random access tasks.
Although the transfer rate increases in multiples, the mean access time does
not. The following table lists transfer rates and access speeds for some
common CD-ROM drives.
CD-ROM Speed
Transfer Rate
Access Speed
4X
600 KB per second
220 ms
6X
900 KB per second
145 ms
8X
1200 KB per second
100 ms
12X
1800 KB per second
125 ms
16X
2.4 MB per second
100 ms
24X
3.6 MB per second
95 ms
Installing CD-ROM and DVD Drives
Installing an internal drive is a four-step process.
1. Install the drive controller or decoder card, if needed, following the
instructions that come with the card.
2. Install the drive in the computer case.
3. Attach the data and power cables.
4. Install the necessary operating system drivers and set up the drive.
Controller Cards
The most difficult part of installing a CD-ROM or DVD drive is determining
which controller card is best for the system.
A quick review of how the computer is currently equipped will guide you in the
selection of the proper card. In most cases, there will be a SCSI or IDE
interface available. Whatever card arrangement you choose, be sure to disable
any other possibly conflicting cards. Confirming the extent of the computer's
resources before purchasing a new CD-ROM drive can save you the time and
frustration of having to return or exchange it.
You should select the controller card before buying the CD-ROM drive because
it must be compatible with both the CD-ROM drive and the motherboard's
expansion slot. There are several ways to ensure a proper connection:
Use the secondary IDE controller on the motherboard.
Install a new controller card (this might be supplied with the CD-ROM
drive).
Install the CD-ROM drive in an existing SCSI chain.
Install a new SCSI host adapter and create a new SCSI chain.
Use an existing sound card with a CD-ROM connection.
Installing an Internal Drive
You can mount both CD-ROM and DVD drives easily in any computer that has
an open bay for a 5.25-inch disk drive. Physical installation is as simple as
installing a floppy disk drive. Most new drives come with a hardware kit that
includes a combination of screws and brackets.
Make sure you have all the tools and parts before beginning. These include:
The drive
The correct cables
The appropriate hardware (including special mounting rails for the PC's
case)
A flat-head screwdriver
A Phillips screwdriver
Needle-nose pliers or tweezers (for jumper settings)
Connecting the cables for a CD-ROM drive is as simple as installing a floppy
disk drive. There are two cables—a flat ribbon cable (for data) and a power
cable. Be sure to connect the flat ribbon cable to the correct location on both
the controller and the CD-ROM drive (with the red wire going to pin 1). If
there are no available power cables, use a Y power splitter cable (this will split
a single Molex connector into two connectors; these are discussed earlier in
Lesson 1 of Chapter 5, "Power Supplies"). There might also be an audio out
cable (two to four wires) that connects to a sound card (see Figure 10.1). This
connection will allow you to take full advantage of the audio capabilities of the
CD-ROM drive.
The cabling for a DVD drive can be a little more complex. Check the
documentation to see how the sound and video are cabled. In some cases you
will have to link the decoder to the video display adapter and link another
loopback to bring the sound through the sound card to the speakers.
If you are adding an IDE-style drive, be sure to set the master/slave jumper as
required (see Lesson 2 of Chapter 9, "Basic Disk Drives"). For SCSI drives, you
must set the proper SCSI ID using either a jumper or switch and make sure
the chain is properly terminated.
Figure 10.1 Cable connections to a typical CD-ROM drive
Software Setup
The file structure for a CD-ROM or DVD drive is different from the directory
used by the MS-DOS file allocation table (FAT). Therefore, you will need a
special driver for MS-DOS to be able to recognize this device as a drive. A
standard device driver supplied by the manufacturer (for BIOS) might also be
required.
Windows 3.x
Microsoft's MSCDEX.EXE, an MS-DOS resident application, provides the
required translation and also specifies the device driver required by the device.
The following changes in CONFIG.SYS and AUTOEXEC.BAT will do the job.
Changes to CONFIG.SYS
To load the device driver, type the following line and include the directory
and driver for the CD to be installed. (The exact name and location of
your driver file might be different from what is shown in this example.)
device=C:\CDROM\MTMCDAI.SYS /D:MSCD001
To ensure drive number assignment space, type the following line. (Note
that the last drive letter assignment and, therefore, the number of drives,
can be limited by assigning a lower value letter.)
lastdrive=z
Add the following line to AUTOEXEC.BAT:
c:\dos\mscdex.exe /d:mscd001 /l:e /m:10
This instruction provides the location of the driver and should include any
switches required to set up the driver. You might have to consult the
documentation for the CD-ROM drive to determine exactly which, if any,
switches are required.
Many CD-ROM drive installation disks will make these changes automatically.
(You can find additional information for configuring CONFIG.SYS and
AUTOEXEC.BAT in Chapter 16, "Operating System Fundamentals.")
Windows 95, Windows 98, and Windows Me
Windows 95, Windows 98, and Windows Me use a 32-bit protected-mode driver
called VCDFSD.VXD. This driver replaced MSCDEX.EXE, the MS-DOS real-mode
driver. When adding a new CD-ROM drive after Windows 95 has been
installed, be sure to use the Add New Hardware Wizard. This wizard will
properly identify and set up the CD-ROM drive. With later versions of Windows
that support the Plug and Play feature, installing a new CD-ROM drive is
simple—the operating system will recognize the new drive and run the install
wizard automatically.
NOTE
If you intend to use a CD-ROM drive in the MS-DOS mode (from a
bootable disk), you will have to install the real-mode drivers and
add them to the CONFIG.SYS and AUTOEXEC.BAT files of the boot
disk.
TIP
You can use a Windows 98 Startup disk to obtain the files required
to recognize a CD-ROM drive. Be sure that the PC has the proper
software licenses to use those files.
Windows NT and Windows 2000
The Windows 2000 operating system offers native Plug and Play support for
most CD-ROM drives. Many can also be configured as bootable devices,
allowing you to install the operating system directly from the installation CDROM. If not, you will have to use the startup floppy disk, along with driver
disks from the vendor to complete an initial installation. For adding a new
drive to an existing system, most new products should have the needed
drivers, and many older products will have drivers as part of the operating
system release. Keep in mind that Windows NT was not as widely supported for
multimedia products, so older DVD drives may not have drivers available, or
some of the features (such as playing movies) may not be supported.
Multimedia
The term multimedia embraces a number of computer technologies, but refers
primarily to video, sound, and the storage required by these large files.
Basically, multimedia is a combination of graphics, data, and sound on a
computer. In all practicality, the concept of adding multimedia simply means
adding and configuring a sound card, a video card, and a CD-ROM or DVD drive
to a system.
Microsoft formed an organization called the Multimedia PC Marketing Council
in 1991 to generate standards for multimedia computers. The council created
several Multimedia PC (MPC) standards and licensed its logo and trademark to
manufacturers whose hardware and software conform to these guidelines.
The Multimedia PC Marketing Council formally transferred responsibility for its
standards to the Multimedia PC Working Group of the Software Publishers
Association (SPA). This group includes many of the same members as the
original Multimedia PC Marketing Council. The group's first creation was a new
MPC standard.
The Multimedia PC Marketing Council originally developed two primary
standards for multimedia: MPC Level 1 and MPC Level 2. Under the direction of
the SPA, the first two standards have been replaced by a third, called MPC
Level 3 (MPC 3), which was introduced in June 1995. There are currently no
plans for the publication of any additional MPC standards. New PCs all well
exceed the limits of the MPC requirements, and all new Windows machines
generally will support a wide range of multimedia applications and hardware.
To run the latest multimedia applications requires at least a Pentium II
machine with a 64-bit sound card, 24-bit display adapter, 20X CD-ROM or DVD
drive, and 64 MB of random access memory (RAM). Speakers able to handle
the features of the sound card are also needed for full use of the system.
Video-Capture Software
With the advent of multimedia computers and software, manipulating fullmotion video was the next logical step. Modern high-speed multimedia
computers have become standard equipment in the moviemaking industry.
Today, even amateur filmmakers can use their computers to give home movies
a touch of professionalism.
Video-capture software provides an interface that allows users to import and
export video formats to edit them with their computers. With this software,
users can view audio waveforms and video images, create files, capture singleframe or full-motion video, and edit video clips and still frames for content and
effects.
File editing functions such as zoom, undo, cut, paste, crop, and clear can be
used to edit audio and visual files. Users can also set the compression controls
to the type of format desired and determine the capture rates. The capture
rate for full-motion video (equivalent to what you would find on TV or on the
big screen) is 30 frames per second (fps), but some systems might not be able
to reach this potential. Professional systems include very large, fast hard disk
drives for data buffering. A typical user of video-capture software might realize
a frame-capture rate of only up to 15 fps without adding an arsenal of
hardware to enhance the system.
Lesson Summary
The following points summarize the main elements of this lesson:
A CD-ROM or DVD drive is now a standard component of a computer
system.
CD-ROM and DVD data transfer rates are based on a factor of 150 KB per
second (1X).
Installing a CD-ROM or DVD drive is little more complicated than
installing a floppy disk drive.
The proper drivers must be loaded before a CD-ROM or DVD drive can be
accessed by the operating system. To run a CD-ROM drive from MS-DOS,
the real-mode drivers must be loaded.
3 4
Lesson 2: Advanced Hard Disk Drives
Chapter 9, "Basic Disk Drives," covered the basics of hard disk drives. In this
lesson, we broaden our discussion of hard disk drives to include the newer
large-capacity drives and several of the newest methods.
After this lesson, you will be able to
Configure the newer large-capacity hard disk drives
Define the limitations of hard disk drives
Identify the advantages and disadvantages of SCSI connections
Estimated lesson time: 45 minutes
Limitations of Early Hard Disk Drives
The original basic hard disk drives—specifically the ST-506—were relatively
simple to install because the primary input/output (I/O) commands were
handled by the PC AT system BIOS. They used the routines built into the
original IBM AT and the same interface command set as the original ST-506
hard drive. As drive capacities grew, they required many changes in setup to
get around the limitations imposed by earlier models. Often, these changes
added to the workload of the processor, which had a net effect of slowing down
the processing of data. This resulted in research for new methods to overcome
those bottlenecks, which in turn led to other design considerations that had to
be addressed. The end result is that storage technology is still evolving. Drives
increase in capacity and speed, causing changes in PC design and operating
system support to take advantage of the larger capacity, faster drives.
IDE and EIDE Drives
IDE drives have been in use since the late 1980s. The purpose of the IDE was
to integrate the drive controller with the drive itself rather than use a separate
controller card. The Advanced Technology Attachment (ATA)—the official name
for IDE drives—standard is based on the original IBM AT standard for hard disk
drives. ATA drives use the same interface command set as the original ST-506
drives and are handled by the system BIOS built into the original IBM AT. ATA
was, and is, a good command set, but its limitations led to its decline as a
viable hard drive interface. These limitations set the stage for the development
of EIDE. The EIDE drive system was developed with two essential objectives:
increasing the size of available disk drives and increasing the speed of data
transfer between the host and the disk drive.
The EIDE specification
Increased the numbers of drives available to the average computer
Increased the data transfer rate
Allowed for non-hard disk drives such as CD-ROM, Zip, and tape drives to
be configured to EIDE standards and be connected to an EIDE controller
Broke the 528-MB storage capacity limit of the ATA standard
NOTE
These remarks apply only to IDE-style drives. SCSI drives and how
they deal with the size and number of drive issues are covered
later in this chapter.
Let's examine these improvements in detail.
Number of Drives
The ATA standard allows two hard disk drives to connect to one common
controller. IBM set aside (reserved) I/O address 1FOh and IRQ 14 for the use
of hard disk drive controllers. IBM also reserved I/O address 170h and IRQ 15
for a second controller (two more hard drives). Early computers had no BIOS
support for this second controller. The BIOS installed on newer computers
takes full advantage of both controllers, allowing up to four EIDE devices.
(You'll find a fuller discussion of addresses and IRQs in Chapter 8, "Expansion
Buses, Cables, and Connectors.")
Most SCSI controllers offer the ability to use IRQ 13 for hard disk drive
support without the use of special drivers. To do so, set the SCSI card with
boot BIOS enabled and make sure the hard disk drive is properly formatted for
the operating system in question.
Data Transfer Rate
ATA drives transfer data to and from the hard disk drive and memory using
standardized protocols called PIO (Programmed Input/Output) modes. With
PIO, data is exchanged between the main memory and a peripheral device, not
by means of direct memory access (DMA), but with in-and-out instructions
through the central processing unit (CPU). The Small Forms Factor (SFF)
standards committee defined these data transfer rates as PIO mode 0, PIO
mode 1, and PIO mode 2. ATA drives can use PIO mode 0, 1, or 2. With each
improved PIO standard, the efficiency and speed of data transfer increased.
The original ATA drives could transfer data from the hard disk drive to RAM at
a maximum rate of roughly 3.3 MB per second. Speed increases to 5.2 MB per
second, and then 8.3 MB per second and beyond, followed shortly thereafter.
Non-Hard Disk Drives
The original controllers allowed only for hard disk drives—and just two of
them. An independent industry group developed the AT Attachment Packet
Interface (ATAPI) to allow non-hard disk drives (CD-ROM drives and highspeed streaming tape units) access to the ATA interface.
The 528-MB Limit
Early BIOSs had a limitation on the maximum cylinder, head, and sector (CHS)
values allowed, and the ATA standard added to that. As a result, for several
years the maximum hard disk drive size was restricted to 528 MB. The
following table shows how CHS limits are determined.
IDE (ATA)
Limit
BIOS Limit
Maximum Usable
Limit
Cylinders
1024
65,536
1024
Heads
255
16
16
Sector/track
63
255
63
Maximum
capacity
8.4 billion
bytes
136.9 billion
bytes
528 million bytes
IMPORTANT
There are two ways to look at 528,000,000 bytes: the marketers'
way (528 MB means 528 million bytes) or the literal way, which
takes into account that there are 1,048,576 bytes per megabyte
(1024 bytes × 1024 bytes). The second way, which is more
accurate, yields a value of 528,000,000 divided by 1,048,576—a
total of 504 MB. Also be aware that an operating system will have
to use part of the space for its housekeeping functions, as well as
command and system files. The actual usable space for application
and data files could be considerably smaller.
EIDE
EIDE specifies the incorporation of four major upgrades to the ATA/IDE
specification:
Logical Block Addressing (LBA) translation standards for BIOSs to support
IDE drives larger than the old limit of 528 MB.
Industry standards for improved data throughput to and from IDE drives—
PIO modes 3 and 4.
Industry standard instruction sets that allow CD-ROM drives and tape
backups to connect to the same controller using the ATAPI standards.
Use of the old, mostly unused IBM standard for a secondary controller
calling IRQ 15 and I/O address 170h.
Overcoming the 528-MB Barrier
There are several methods used to overcome the 528-MB hard disk barrier.
When developing these methods, the difficult task was to create novel ways to
access more data while maintaining backward compatibility. In most cases,
designers found ways to address larger drives while "fooling" the operating
system into functioning as if the drive were still within the proper limits.
When working with high-capacity drives, the computer professional must
understand these different methods and apply the best method for a given
situation. This is especially true if you encounter a situation in which different
oversized drives are installed in an older system; these older systems often
require special drivers or partitioning software. Using multiple hard disk drive
drivers can confuse older operating systems due to incompatibilities. Never use
drive data compression software in such cases without being sure that all the
code involved is compatible.
IMPORTANT
The new, super-large hard disk drives might not work with some
older machines. They will run, but will not take advantage of the
extra high capacity.
Logical Block Addressing
LBA is a means of addressing the physical sectors on a hard disk drive in a
linear fashion. A translating BIOS detects the capacity of the drive and
manipulates the CHS values so that the cylinder value is always less than
1024. Here's how it works:
Before LBA (limit 528 MB):
capacity = cylinders × heads × sectors per track
528,482,304 = 1024 × 16 × 63 × 512
With LBA:
cylinders = capacity divided by (heads × sectors per track)
When the computer boots up, an enhanced drive parameter table is loaded
into memory. When data is transferred, this table intercepts the request and
converts the system's CHS values to LBA values that the computer's BIOS can
handle.
Enhanced CHS Translation
Enhanced CHS is a standard that competes with LBA. This standard allows
drives to be manufactured a little faster and more easily than LBA. IBM and
other manufacturers support this standard.
Fast ATA
Fast ATA uses PIO mode 3, while Fast ATA-2 uses PIO mode 4. It is a
technique used by Seagate Technologies (and others) to compete with EIDE.
Fast ATA drives will support either LBA or CHS drive translation to break the
528-MB barrier.
Logical CHS and Physical CHS
Logical cylinders, heads, and sectors (LCHS) is a value used by the operating
system (MS-DOS, Windows 95, Windows 98, OS/2, and so forth) to determine
the size of the hard disk drive. Physical cylinders, heads, and sectors (PCHS) is
a value used within the device to determine its size. A translating BIOS and
the operating system use different algorithms to determine the address of the
data.
DMA Transfer
DMA is a transfer method that, although not a PIO mode, also works to
overcome the size limitations of hard disks. DMA bypasses the CPU to transfer
data directly into memory. This is the preferred way to move large chunks of
data in a multitasking environment. UNIX and Windows NT take advantage of
DMA transfers. These transfers can function by using either the DMA controller
on the Industry Standard Architecture (ISA) bus or a bus-mastering controller
that takes over the expansion bus and bypasses the built-in DMA controller.
DMA data transfers can be either 16 bits (single word) or 32 bits (double word)
wide. The transfer width depends on the data bus used—ISA, EISA, or VLB
(see Chapter 8, "Expansion Buses, Cables, and Connectors" for details). DMA
data transfer for ATA hard disk drives is extremely rare.
Be warned, however, that using DMA data transfer can lead to data loss,
although this should be a concern only when transferring partitioned and
formatted hard disk drives between computers that use different BIOSs to
make the translation. The following table shows the various DMA modes.
DMA Modes
PCHS
LCHS
Cylinders
2304
576
Heads
8
32
Sectors/track
63
63
Capacity
594.5 million bytes
594.5 million bytes
Breaking the 8.4-GB Barrier
Hard disk drives larger than 8.4 GB require a BIOS that supports enhanced
interrupt 13h extensions for very large drives. Which method is used will
depend on the system's age, operating system, and the drive in question.
Newer machines come with built-in support in the system BIOS. There are
three methods you can use to enable this function on older PCs that do not
come with native support:
Upgrade the system BIOS
Install a hard disk drive adapter with interrupt 13h support
Use a software program from the drive maker to allow the system to
access the drive
Depending on the system BIOS, you might not be able to display the entire
size of the drive while in BIOS/CMOS Setup. Check the manual for the BIOS
and operating environment for more details.
The procedures just described will let the system recognize the drive, but the
maximum partition size will still be determined by the operating system in
question. Be sure to check the procedures for the version you will be using
with any third-party software. Newer versions of Windows (98, Me, NT, and
2000) allow very large partitions.
If you use an older version of the MS-DOS FDISK utility to prepare the drive,
you will not be able to use the entire contents as a single volume. If you use
Microsoft's FAT12- or FAT16-based FDISK, the largest single partition will still
be 2.1 GB unless a third-party partitioning program is used. Newer versions of
Windows can access partitions greater than 2.1 GB, but if you plan to use a
dual-boot configuration, be sure that any partition is compatible with the
operating system you want to use to view the files it contains. NTFS and
FAT32 partitions are not visible to older versions of Windows, MS-DOS, or
UNIX.
Ultra DMA
Although questions about the latest incarnation of ATA/DMA drives are not
likely to appear on the current A+ Exam, a good computer technician should
be conversant with them and expect to see them as part of the certification
renewal process. Ultra DMA/33 is a faster drive technology that can be used on
virtually any Pentium motherboard. Ultra DMA/66 offers raw data transfers at
twice the speed of its older DMA/33 sibling. It requires a compatible system
bus on the motherboard (or a special controller card), BIOS, and special IDE
cable certified for that speed. They are easy to identify. One 40-pin connector
is blue, and the other is black. Most are also labeled for Ultra DMA/66.
Installing EIDE Drives
Installing an EIDE drive is similar to installing an ATA drive, but in your
presetup examination, you should consider secondary controllers, proper
translations, and verifying PIO modes on older systems. Before undertaking an
installation, you should collect all the information from the new drive as well
as from the existing drive. Consider all the options on paper before removing
any screws. If you don't have enough information on hand, consult the drive
manufacturer or resources on the Internet. If you are installing a very new
EIDE or Ultra DMA drive on an old system, make sure the motherboard,
Peripheral Component Interconnect (PCI) bus, cables, and IDE interface are
compatible with the drive specification.
Secondary Controllers
Many EIDE I/O cards support secondary controllers, allowing for up to four ATA
devices, as mentioned earlier. Before installing a card, be sure that jumper
settings are set properly (see Figure 10.2). Secondary controllers are always
set at I/O address 170h and IRQ 15.
Many cards come preset with the secondary controller disabled. Also check the
advanced CMOS settings to make sure that any secondary controller enable/
disable options are set to enabled.
NOTE
Some EIDE controller cards require that the CMOS options for
secondary port hard disk drives be left as "Not Installed." Be sure
to read all documentation that comes with these cards.
Figure 10.2 Controller card with jumpers
Secondary IDE interface and on-board channels are best suited for use with
CD-ROM, DVD, or tape drives. Many secondary controllers on older machines
run at a lower PIO mode (0 or 1) than the primary controller (3 or 4). It is
always best to check the documentation before installing.
LBA or CHS?
Most BIOSs can support both LBA and CHS. Enhanced BIOS allows the system
to get around the MS-DOS limitation of 528 MB per hard disk and is the
easiest way to install an EIDE drive. An enhanced BIOS will support either the
Western Digital LBA mode or the Seagate Extended CHS mode.
NOTE
The two translation options are not interchangeable. You cannot
partition a drive in one computer using one option and move it to
a system that uses the other option. Also, see the earlier
information about drives of over 8.4-GB capacity. CHS settings are
not "real" for drives larger than that size, and they must use some
form of controller, system, or third-party software translation to
work.
What if a computer does not support either CHS or LBA? Most newer, largecapacity drives will provide a disk manager disk, or the ability to make one
from the drive itself. (If the information is on the disk, you will be able to
access a small MS-DOS partition with the data. The instructions for accessing
this data are very specific and must be followed according to the
manufacturer's requirements.) This software, when installed properly,
performs the same task as CHS or LBA. When using this method, you need to
first answer this question: Is the drive in the master or slave position?
If it is in the slave drive, install the appropriate driver in the CONFIG.SYS
file, if required by the operating system.
If it is in the master drive, the driver must be loaded before anything
else, including the CONFIG.SYS file. You can accomplish this by changing
the Dynamic Drive Overlay (DDO) in the master boot record. The
software provided by the drive manufacturer should make these changes
for you.
There are some drawbacks to using this method rather than LBA or CHS:
Microsoft no longer supports the use of DDO software.
When booting up from a floppy disk, for the hard disk drive to be
accessible, the device must be loaded from the floppy disk's CONFIG.SYS
file.
A virus might attack the master boot record, where this file resides. This
can cause serious problems and at the very least will require
reinstallation of the DDO file. Always keep a bootable, virus-free floppy
disk on hand.
The driver that allows use of a large hard disk drive might also use a
large chunk of conventional memory. The trade-off might not be worth it.
Many hard disk drive repair programs cannot be used with DDO.
The software might cause conflicts with the operating system or other
drivers.
Setting PIO Mode
There are five PIO modes. A drive must be set properly to achieve the best
performance. The following table shows the parameters of PIO modes.
PIO
Mode
Cycle Time in Nanoseconds
(ns)
Transfer Rate (MB per
second)
0
600
3.3
1
383
5.2
2
240
8.3
3
180
11.1
4
120
16.6
Answer the following questions before setting the mode:
What is the fastest mode supported by the hard disk drive?
What is the fastest mode supported by the controller?
What is the fastest mode supported by the BIOS or device driver?
CAUTION
The maximum achievable PIO will be limited by the slowest
component. Setting a mode that is too fast will not damage the
driver, but it might damage your data.
To set up the PIO mode:
Determine the PIO of the drive. This is preset by the manufacturer and
cannot be changed. See the documentation that comes with the product
or visit the vendor's Web site for details if it is not on the drive or handled
by the system BIOS.
Determine the fastest speed your controller can handle. Most hard disk
drives can support PIO mode 2. If you're using an ISA card, PIO mode 2 is
the highest PIO available. The two fastest PIO modes, 3 and 4, must be
run from either a VESA local bus (VLB) or a PCI controller. Be careful
with on-board controllers! On PCI systems, almost all on-board controllers
are PCI; on VESA machines, they are VLB.
Use the BIOS Setup program to adjust the CMOS settings. If auto setup
(where the firmware can auto-detect the drive parameters and set the
BIOS) is available, use it.
PIO modes 3 and 4 use a hardware flow control called IORDY (I/O
ReaDY), also known as IOCHRDY. This setting allows the drive to slow
down the data transfer as the head moves across the disk.
Other Settings
There are several other drive settings that are not necessarily limited to EIDE
but are generally associated with these larger hard disk drives.
Multiple Block Reads
The ATA standard requires each drive to activate its IRQ (see Chapter 8,
"Expansion Buses, Cables, and Connectors" for details of IRQ) every time it
sends one sector of data. This process helps to verify good data transmission,
but it slows down the computer. Multiple block reads speed up the process by
reading several sectors of data at a time.
Many BIOS chips have multiple block read as an advanced feature. Enabling
multiple block read can be done with third-party utilities as well. Multiple block
read can also be installed using a device driver that comes with a hard disk
drive controller. Always use multiple block read, if possible.
32-Bit Access
Providing 32-bit disk access is a major speed improvement over MS-DOS for
the Windows 3.x and Windows for Workgroups 3.11 environments. Every time
an operation is performed under Windows, Windows must use the BIOS
routines to access the hard disk drive. To do this, it creates a virtual MS-DOS
world, a "bubble" of conventional memory that looks and runs just as if the
machine were running MS-DOS.
Enabling 32-bit file access allows later versions of Windows 3.x to talk directly
to the ROM BIOS, using a protected-mode driver called VFAT.386 (found in the
Windows\System directory). VFAT.386 is loaded using the [386Enh] section of
the SYSTEM.INI file. With the 32-bit file loaded, Windows does not have to
create an MS-DOS "bubble" to talk to the hard disk drive.
For 32-bit file access to work in older versions of Windows:
1. Enter the line
device=c:\windows\ifshlp.sys
into your CONFIG.SYS file. This loads the 32-bit file access driver.
2. In the SYSTEM.INI file, add two lines to the [386enh] section:
device=vfat.386
device=vcache.386
(These protected-mode drivers replace MS-DOS FAT functions and
SMARTDRV.EXE functions.)
NOTE
Windows 95 and later versions of that operating system
automatically install a 32-bit file access driver. 32-bit file access is
transparent to EIDE and requires no special settings.
There are some other potential problems with Windows 3.x and large drives.
Windows 3.x uses a file called *WDCTRL for 32-bit disk access. This file is
enabled from the SYSTEM.INI [386enh] section. This driver predates LBA and
will generate the error: "32 file access validation failed." If this happens,
*WDCTRL needs to be updated. Most EIDE controllers and all drives now come
from the factory with a software disk that should include the latest drivers. If it
is not available on your disk, look up the Web site of the hard disk drive
manufacturer and download the driver.
Whenever possible, check the CMOS, look for a 32-bit disk access option, and
enable it.
Lesson Summary
The following points summarize the main elements of this lesson:
Originally, hard disk drives were limited to storage capacity that did not
exceed 528 MB.
Using new technology, the old hard disk drive limit has been exceeded.
Modern computers allow up to four IDE drives to be installed on built-in
controllers.
Properly setting PIO will enhance the performance of a drive.
32-bit disk access provides a major speed improvement for disk drives.
3 4
Lesson 3: SCSI Drives
SCSI has become the mass-storage device of choice for large network
installations. SCSI, first introduced in Lesson 2 of Chapter 9, "Basic Disk
Drives," has many advantages over standard IDE and EIDE drives. SCSI is the
favored drive for high-end workstations, network and Internet servers, and the
Macintosh line of personal computers. In many installations, the advantages
far outweigh the slight extra effort in configuration. In this lesson, we explore
the advantages and uses of a SCSI system.
After this lesson, you will be able to
Define the advantages and disadvantages of a SCSI system
Determine whether a SCSI system is best for your client
Set up a SCSI system
Estimated lesson time: 30 minutes
SCSI was introduced in 1979 as a high-performance interface, allowing
connection of both internal and external devices. Because it runs on virtually
any operating system, it was adopted by the American National Standards
Institute (ANSI) Standards Committee and is now an open standard in its third
generation.
At its core, SCSI is a simple design. A single card, the host adapter (or a chip
set on the motherboard) connects up to 15 devices. These devices can be
attached inside or outside the PC using standard cables and connectors. SCSI
is the only interface that can connect such a wide variety of devices.
Communication between the devices and the host adapter is done without
involving the CPU or the system bus until data must be passed to one or the
other.
This design frees expansion slots and reduces the number of interrupts and
memory addresses needed, while cutting down the number of drivers required.
Less robust solutions, such as IDE and EIDE, are little more than switching
stations, relying on the PC's CPU to manage the data bus. SCSI host adapters
are true subsystems with advanced commands that can order and route data
to improve performance.
SCSI-1
In the late 1970s, Shugart Associates developed an interface to handle data
transfers between devices, regardless of the type of device. The interface
operated at the logical—or operating system—level instead of at the device
level. This new interface was called the Shugart Associates System Interface
(SASI)—the precursor to SCSI.
In June 1986, the ANSI X3.131-1986 standard, known as SCSI-1, was
formally published. This was a very loose definition, with few mandates. As a
result, manufacturers of SCSI products developed a variety of competing
designs.
SCSI-1 supported up to seven devices on a chain (plus the host adapter), each
of which transferred data through an 8-bit parallel path. Compatibility of SCSI
drives was nearly impossible because many SCSI devices had their own
custom commands on top of the limited SCSI standard.
You might encounter older SCSI adapters, drives, and peripherals that are
based on the original SCSI-1 standard. In reality, this standard amounts to
little more than a few agreed-on commands. The wide range of proprietary
drivers, operating system interfaces, setup options, and custom commands
made true compatibility a real problem and gained SCSI a bad reputation on
the PC platform. It was, however, popular with Apple and UNIX developers,
who could work with a limited range of devices.
In most cases, it is best to upgrade any SCSI-1 devices to SCSI-2. If
circumstances require you to work on an early SCSI product, you will have to
contend with both hardware and driver issues. Check the Web site of your
SCSI device's manufacturer for possible new drivers.
SCSI-2
The limited acceptance, but great potential, of SCSI-1 led to a more robust
standard with a range of commands and a layered set of drivers. The result
was a high-performance interface that began to take over the high-end
market. It was the interface of choice for fast hard disk drives, optical drives,
scanners, and fast tape technology.
One of the most important parts of the SCSI-2 specification is a larger (and
mandatory) standard command set. Recognition of this command set (18
commands) is required for a device to be SCSI-2 compliant. The Common
Command Set (CCS) made compatibility of multivendor devices possible. The
CCS also introduced additional commands to more easily address devices such
as optical drives, tape drives, and scanners.
SCSI-2 also supports:
Wide (16-bit) SCSI
Fast SCSI
Fast/Wide (combines fast and wide features)
Ultra (32-bit) SCSI SI-2
Backward compatibility with SCSI-1
Fast SCSI-2
This standard uses a fast synchronous mode to transfer data, doubling the data
transfer speed from 5 MB/s to 10 MB/s. Wide SCSI doubles that again.
Plug and Play SCSI adapters first arrived with the advent of the SCSI-2
standard. Today, all new SCSI host adapters are Plug and Play. The SCSI-2
standard took a long time to gain final approval, requiring agreement by many
vendors. As a result, you might run into products labeled "Draft SCSI-2." In
almost all cases, you can get these products running on any SCSI-2 or later
system if you get the appropriate drivers from the vendor or the maker of the
host adapter or operating system.
SCSI-3
To speed the pace of development, the SCSI Committee approved a "fasttrack" system for the SCSI-3 standard. A subcommittee handled most of the
work, and new subsections were adopted without waiting for the publication of
the entire SCSI definition.
That bright idea, plus the advent of the PCI bus and mature Plug and Play
operating systems, has made it easy to install components and has given users
excellent control and flexibility. All SCSI-3 cards have ways to support existing
SCSI-2 devices. Some of the highlights of current state-of-the-art SCSI
technology on the desktop include the following seven features.
High-Performance Products
The success and stability of the SCSI standard makes it an ideal platform for
developing high-performance products. SCSI's robust, reliable interface and
advanced commands allow manufacturers to build "best-of-breed" products to
take advantage of its power. The fastest hard disk drives and CD-ROM devices
traditionally show up first, sporting a SCSI interface. The most advanced
scanners are SCSI-based, and many optical products come only in SCSI
versions. Even when non-SCSI versions reach the market, they generally
underperform their SCSI siblings.
Plug and Play Installation
Well-designed SCSI cards are recognized and drivers are installed
automatically with Plug and Play operating systems such as Windows 98,
Windows Me, Windows NT, Windows 2000, and the Macintosh OS. Most SCSIbased peripherals provide Plug and Play setup. The first time the system is
booted up after a peripheral is added to a SCSI chain, the system notices the
new device and asks for the product's setup disk.
Simple Expansion
Adding external devices is as simple as connecting an industry standard cable
and power cord. If users decide to add additional host adapters, they can share
the same drivers, reducing system overhead.
Advanced Management
SCSI products generally offer a range of tools to tune the bus and devices
attached to it. For example, many host adapters have firmware that provides
the ability to format and inspect hard disk drive reliability and define custom
settings for each device on the chain. Operating system utilities are provided
to check the status of a device and enable advanced features.
SCAM Support
SCAM stands for "SCSI configured auto-magically." Most new SCSI products
are SCAM-enabled, meaning that the user does not have to worry about
setting the ID numbers for them because they will configure themselves using
an open ID position on the SCSI chain.
NOTE
Even if a hard disk drive is SCAM-enabled, you might have to set
an ID on multidrive PCs because the host adapter will need it to
determine which drive is the normal boot device.
Connect/Disconnect
This command allows a SCSI device handling a large amount of data or
performing complex operations to disengage from the host adapter's bus while
performing the task, allowing other devices free access until it is finished.
Tag Command Queuing
SCSI devices with this feature can reorder how blocks of data are moved on
the bus to speed transfer. This function compares to letting a shopper with
only a few items move to the head of the checkout line to reduce the average
wait time per shopper.
The table below offers a quick guide to the basic differences between SCSI and
IDE.
SCSI and IDE Compared
Feature
Devices per channel
SCSI
7/15 per chain
Ultra
DMA/IDE
2 per chain
66 MB per
160 MB per
second (Ultra
160)
80 MB per
second (Ultra2)
40 MB per
second (Wide
SCSI)
second (Ultra
DMA)
33 MB per
second (Ultra
DMA)
16.7 MB per
second (Fast
ATA)
Connection types
Internal and
external
Internal only
True bus mastering
Yes
No
Operate more than one I/O device at a
Yes
time?
No
Advanced commands (such as tag
command queuing,
connect/disconnect)
No
Maximum potential throughput for
major classes of SCSI and IDE
Yes
Noise and SCSI
Any electrical signal other than data is called noise. Due to the many signals
and electrical devices present, the interior of a computer is a noisy place.
Computer manufacturers do many things to contain the noise inside the case,
including adding shielding and grounding. Anything inside, or directly
connected to, a computer is either a contributor to or a victim of the noise.
Because of the high data transfer speed, products using the SCSI-2 and later
standards can be very sensitive to noise. Cables tend to act as antennae for
noise. For this reason, proper cabling and minimizing of cable length are
needed to maintain low noise in a SCSI system. Any noise spread through
either the electrical power cables or the data cable is called common-mode
noise.
A single-ended device communicates through only one wire per bit of
information. This one wire is measured, or referenced, against the common
ground provided by the metal chassis. Single-ended devices are vulnerable to
common-mode noise (they have no way of telling the difference between valid
data and noise). SCSI-1 devices are all single-ended.
Some SCSI-2 and SCSI-3 devices are differential-ended. These products
employ two wires per bit of data—one wire for the data and one for the inverse
of the data. The inverse signal takes the place of the ground wire in the singleended cable. By taking the difference of the two signals, the device is able to
reject common-mode noise in the data stream.
CAUTION
Under no circumstances should you try to connect single-ended
and differential-ended devices on the same SCSI chain. You might
fry the single-ended device and, if the differential-ended device
lacks a security circuit to detect your mistake, you will probably
destroy it as well.
Troubleshooting a Device Conflict
Determine which is the offending device by taking the following measures:
Load only the device drivers for the SCSI devices.
If the problem still occurs, use the F8 key to determine which driver
conflicts. (Press F8 when starting MS-DOS, Windows 95, Windows 98, or
Windows Me. This will allow step-by-step confirmation of the startup
process.)
If the device driver is an executable file, try running it with the /? option.
This will usually show a variety of command-line switches for the device
driver (for instance, MOUSE.EXE /?). For more details on MS-DOS
command programs and switches, see Chapter 16, "Operating System
Fundamentals."
Here are some ways to correct the problem after you've found it:
Look in the manuals or Readme files of both devices. The problem might
be a common one with a known solution.
Try a variety of switches to see if any of them solves the problem.
Attempt to find an updated driver for one or both of the devices (the
Internet is a good place to look).
If none of those solutions fixes the problem, you might be forced to
choose between the devices or go to a multiple boot configuration.
Memory Management
SCSI host adapters typically have their own ROM chips. For MS-DOS systems,
put the appropriate "X=" statements in the EMM386.EXE line of the
CONFIG.SYS and the appropriate EMMEXCLUDE= statement in the SYSTEM.INI
file. (For more details about configuring these files, see Chapter 16,
"Operating System Fundamentals.") A missing or erroneous "exclude"
statement can cause intermittent lock-up problems.
Costs and Benefits of SCSI
Initially, the cost of a SCSI system and SCSI devices is greater than the costs
involved in IDE. However, there are several environments in which a SCSI
system might justify the increased cost. Some ideal uses for SCSI include:
File servers
Workstations (both graphical and audio)
Multitasking systems
Systems moving large amounts of data among peripheral devices
Systems with a large number of peripheral devices
Systems requiring fault tolerance (mostly file servers)
The Future of SCSI
SCSI continues to be the device of choice for systems in which speed and
compatibility are important. The ability of the SCSI format to provide fast and
efficient fault tolerance for network systems through the use of redundant
array of independent disks (RAID) will keep it the drive of choice for networks.
Although it is not required, the SCSI drive is generally preferred over IDE by
Windows NT and 2000 system designers for its performance and flexibility.
SCSI continues to be more expensive than IDE, but SCSI's ability for RAID, hot
swapping (changing drives without shutting down a system), and machine
independence will keep it popular for workstations and servers.
Setting Up a SCSI Subsystem
There are several steps in setting up a SCSI-based system or adding a new
SCSI peripheral to an existing system. Performing these steps in the proper
order, without shortcuts, is the key to a fast, easy installation.
Start with the Host Adapter
SCSI cards come in a wide variety of sizes, shapes, and configurations. Some
offer one connection, whereas others have four. Options include secondary or
even tertiary channels—RAID, cache RAM, and so forth. Be sure that the card
will be able to service the devices planned for it. Begin by setting the jumpers,
then install the SCSI adapter card in the appropriate expansion slot.
Set the SCSI IDs, Termination, and Peripheral Cabling
Write down the ID for each device—including the host adapter—as it is
assigned. After the IDs are set, verify termination for each end of the chain.
Finally, attach the cables—first to the host adapter, then to the closest internal
device—and move outward on the chain. Repeat the process for the external
devices.
External devices usually use some form of switch to set the ID. Most allow
setting IDs from 0 through 7 only. You might need to adjust that with internal
devices that often allow a wider range of ID numbers. Cable types include 50pin Centronics type, SCSI-2 D-Shell 50, and 68-pin type connectors. Make
sure the last device in the chain is properly terminated.
Internal SCSI devices are installed inside the computer and are connected to
the host adapter through an interior connector on the host adapter. Check the
connection diagram to be sure the fitting is the right one for that type of
device. The options are a 50-pin ribbon cable (similar to a 40-pin IDE cable)
and two similar 68-pin cables. Be sure to use the right type of 68-pin cable:
One is for ultra-low voltage differential and the other is for single-ended
drives. They are not interchangeable.
IMPORTANT
Connecting a SCSI device incorrectly (for instance, with the cable
plugged backwards) can cause damage! Be sure the red or blue
strip on the cable is facing toward pin 1. Some SCSI devices allow
only a proper connection.
Power Up One Device at a Time
It is good practice to connect the power to one device, power up, and check for
problems. Power up additional devices one at a time and make sure everything
is working and without conflict.
Load Operating System Drivers and SCSI Software
Finally, load any software required to allow the operating system to recognize
the new hardware and take full advantage of its features.
Using a cable with enough connectors enables you to easily link multiple
internal devices. You can have up to eight (numbered 0–7) devices, or 16
(numbered 0–15, depending on the host adapter and the devices) on a single
SCSI chain. Don't forget that the host adapter takes up one position in each
SCSI chain. Figure 10.3 shows a SCSI chain.
Figure 10.3 SCSI chain
The exact number of devices will vary depending on a number of conditions.
The host adapter must support the number selected, the installer must be able
to set proper IDs, and the cables and connectors must be compatible. Older
adapters allow only seven total IDs, and the card will use one, leaving you
with six devices. Some SCSI devices have limited ID options. Many older
products have only seven possible settings; some scanners or optical products
are factory-set to an ID. Given the range of cable options and performance
considerations, you might have to limit the number of devices on a single
chain to get maximum performance.
Setting SCSI IDs
A simple SCSI chain works like a network, and, like a network, each device
requires its own unique address. Unlike a network, however, setting an
address on a SCSI chain is simple. A SCSI device can have any ID number in a
range recognized by the host adapter, as long as no other device on the same
chain has been set to the same number.
In SCSI numbering conventions:
The host adapter is typically set to SCSI ID 7. (This is a de facto standard,
not a requirement.)
There is no mandated order for the use of SCSI IDs, but the SCAM
feature will use a preestablished pattern of IDs if one is available.
The host adapter manufacturer may preset the ID of a bootable hard disk
drive. Most manufacturers use SCSI ID 0, although a few are configured
to SCSI ID 6.
Setting a SCSI ID for a device is accomplished using jumpers or switches
located on, or inside, the SCSI device. Typically, all internal SCSI hard disk
drives use jumpers to set their IDs. External devices usually (but not always)
have switches. Some SCSI devices have automatic ID and termination, using
SCAM.
CAUTION
Some external devices will offer a limited number of choices. This
lack of choices could cause problems when the chain is full. You
might then have to adjust other drive IDs to find a unique ID for
the new drive.
If you plan to utilize a SCSI drive as your C drive (this is required if you want
to boot from this drive), it must be configured as a bootable drive. You can do
this by either specifying the host adapter as the "bootable" SCSI ID or setting
the host adapter to emulate a standard AT-style controller.
Logical Unit Numbers
It is possible to have a single SCSI ID support more than one device. Logical
unit numbers (LUNs) can be used to provide a unique identifier for up to seven
subunits per ID number. These are used primarily in hard disk drive arrays to
create one large logical drive out of several smaller physical drives. LUNs
require highly specialized software and are most often found in network
servers running Novell NetWare, Windows NT, Windows 2000, or UNIX.
Termination
Whenever you send a signal through a wire, some of that signal will reflect
back up the wire, creating an echo. To terminate a device simply means to put
a terminating resistor on the ends of the wire. The purpose of this terminator
is to prevent the occurrence of this echo. Two kinds of termination are used in
SCSI technology: active and passive. Most older (and all SCSI-1) devices use
passive termination. Proper termination of a SCSI device requires special
consideration. Older hardware can be damaged by improper termination but,
more often, lack of proper termination will result in a boot failure or the failure
of the system to recognize a device that has been connected to the SCSI
chain.
On most devices within a computer, the appropriate termination is built–in. On
other devices, including SCSI chains and some network cables, termination
must be set during installation. The only absolute termination rule is that both
ends of the chain must be terminated and that devices that are not on either
end must not be terminated. Most SCSI devices come equipped with some
form of termination. For most internal products, jumpers can be set to enable
termination and connectors can be attached to cables that lead to one of the
two SCSI connectors on an external device. Internal Ultra-SCSI 80 and UltraSCSI 160 drives do not have termination options on the actual devices. A
termination block on the end of the cable handles their termination.
Most new SCSI host adapters are equipped with autotermination circuitry,
which polls the chain and sets the proper termination at their ends (or
middles). On older cards, you might have to set jumpers. Check the manual
for any SCSI device you are installing for instructions on how to set
termination and ID before powering it up.
Lesson Summary
The following points summarize the main elements of this lesson:
SCSI was introduced in 1979 as a system-independent means of mass
storage.
A SCSI chain is a series of devices that work through a host adapter.
SCSI chains can have up to 8 devices, including the host adapter (or 16,
depending on the configuration) connected together.
SCSI chains must be terminated on both ends.
SCSI is used with many different types of peripherals, including printers,
scanners, hard disk drives, and tape units.
Bus mastering is a method used by SCSI to transfer data independently of
the CPU.
RAID uses several SCSI hard disk drives to provide improved performance
and fault tolerance for data storage.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
CD-ROM and DVD Drives
CD-ROM data transfer rates are based on a factor of 150 KB per second.
Before a processor can access a CD-ROM drive, the proper drivers must
be loaded.
To run a CD-ROM drive from MS-DOS, the real-mode drivers must be
loaded.
CD recordable technology allows end users to create their own CD-ROM
disks using a variation of write-once, read many.
CD RW (read/write) takes CD recordable one step further with CD platters
that can incorporate write-many, read-many.
DVD is an extension of CD-ROM technology, allowing a much more
densely packed disk.
DVD can be used to store data, multi-media, and full-length motion
pictures with multiple soundtracks.
Advanced Hard Disk Drives
For many years, hard disk drives were limited to 528 MB.
There are four ways to overcome the 528-MB barrier: LBA, Enhanced
CHS translation, Fast ATA, and DMA transfer.
EIDE controllers and I/O cards support up to four EIDE drives including
hard disk drives, tape drives, CD-ROM drives, and removable disk drives.
SCSI Drives
SCSI chains can have up to 8 devices, including the host adapter (or 16,
depending on the configuration) connected together.
SCSI chains must be terminated at both ends.
Each device in a SCSI chain must have a unique ID.
RAID uses SCSI drives to provide improved data storage and fault
tolerance.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Name four methods of overcoming the 528-MB hard disk limitation.
2. How do multiple block reads speed up a computer?
3. How many devices can be installed on a SCSI chain?
4. What is the effect of improper termination on a SCSI chain or device?
5. Sometimes the SCSI device driver conflicts with other drivers. What steps
need to be taken to resolve the problem?
6. Describe three advantages of using a CD-ROM drive.
7. What are the four steps required to install a CD-ROM drive?
8. Is a 16X CD-ROM drive 16 times faster than a 1X? Why?
9. How would you determine which type of CD-ROM drive to install in a
computer?
10. Why would you use the MSCDEX.EXE real-mode driver with Windows 95?
11. Instead of using magnetic energy for storing data, a CD-ROM uses
___________________ technology.
12. Name some possible controller card combinations.
13. What software is required for a CD-ROM drive installation?
Answers
3 4
Chapter 11
The Display System
About This Chapter
Early personal computers employed text-based displays, offering green, white,
or amber characters against a black background. Today the average PC
monitor can provide life-like colors and reproduce images of near-photographic
quality. In some cases, more compact flat-panel displays have replaced bulky
monitors. This dramatic change is the result of radical improvements in
monitors and the display-adapter technology that drives them. This chapter
discusses how these devices work in unison to provide an acceptable display
for applications ranging from simple desktop productivity tools like word
processors to advanced graphics workstations that can create life-like
animations for big-screen movies.
Before You Begin
An understanding of the principles of memory, expansion bus types, and
expansion cards is essential. If you need a refresher course on these subjects,
review Chapter 7, "Memory," and Chapter 8, "Expansion Buses, Cables, and
Connectors."
3 4
Lesson 1: Monitors
In this lesson, we discuss today's most obvious and necessary computer output
device: the display screen. For most desktop users, this is a monitor. It is
important for the computer technician to understand the basics of how
monitors work and how they are adjusted. In many cases, a simple
modification can correct a problem; in others, the intervention of a specially
trained technician is required. This lesson focuses on traditional monitors,
which still have the lion's share of the display device market.
After this lesson, you will be able to
Identify the various types of monitors
Recognize the components of monitor resolution
Determine the amount of video memory your system requires
Troubleshoot common monitor problems
Estimated lesson time: 20 minutes
Basic Monitor Operation
A monitor operates fundamentally like a TV set, except that it is designed to
receive signals from a card in the PC, rather than a broadcast signal. A variety
of design factors and the features of a monitor's companion adapter card
influence the quality of a monitor's display.
CAUTION
Repairing the inside of monitors is a job more in the realm of a TV
repairman than a computer technician. Monitors generally carry
warnings that they contain no user-serviceable parts for good
reason. Although we discuss the inner workings of monitors in this
chapter, do not take this as an invitation to probe inside them
because of the high risk of serious electrical shock.
The CRT
The CRT (cathode-ray tube) is the main component of a traditional monitor.
The rear of the CRT holds a cylinder that contains one or more electron guns.
Most color monitors have three guns in back—one for each of the colors red,
green, and blue. This combination (usually referred to as RGB) allows the
visual production of all colors.
The wide end of the CRT is the display screen, which has a phosphor coating (a
substance that can emit light when hit with radiation). When active, the guns
beam a stream of charged electrons onto the phosphorus coating. When the
coating is hit with the right amount of energy, light is produced in a pattern of
very small dots. This same technology is used in X-ray imaging, oscilloscopes,
and other CRT devices. Similarly, monitors emit X-radiation. There is one dot
for each primary color (RGB), and the dots are grouped in patterns close
together. The name for a collection of all dots in a specific location is a pixel
(which stands for picture element).
Image Formation and Refresh Rates
The human eye perceives the collection of pixels painted at the front of a CRT
as a compound image, in much the same way as it interprets the pattern of ink
dots in a newspaper halftone as a photograph. The term persistence is used to
define how long the phosphors on the screen remain excited and emit light.
The image on the screen is not painted all at once. The stream is directed in
rows, usually starting in an upper left corner. A series of raster lines are drawn
down the face of the screen until the beam reaches the lower right, whereupon
the process starts over. The persistence rate (how long a given line is visible)
must hold for long enough to allow formation of a complete image, but not so
long that it blurs the dots painted in the next pass.
These raster passes take place very quickly. The time required to complete a
vertical pass is called the vertical refresh rate (VRR); the time required to pass
once from left to right is known as the horizontal refresh rate (HRR). Generally
speaking, faster is better. If the vertical rate is too slow, it can cause flicker,
which is not only annoying, but can lead to eye strain. The larger the CRT, the
faster the refresh rate must be to cover the entire area within the amount of
time needed to avoid flicker. At 640 × 480 resolution, the minimum refresh
rate is 60 Hz; at 1600 × 1200, the minimum rate is 85 Hz. Both the monitor
and the display adapter produce the refresh rate, shown in Figure 11.1.
Figure 11.1 Horizontal and vertical refresh rates
Early monitors had fixed refresh rates. In 1986, NEC introduced the first
multifrequency monitor that could automatically adjust the refresh rate to take
advantage of the highest rate supported by the display adapter of that time.
NEC used the term "MultiSync" to trademark name its line of multifrequency
monitors. Today, this feature is standard on most monitors.
CAUTION
Do not exceed the approved refresh rate for a monitor, even if the
adapter can produce a higher scan of the screen. The result will be
an unstable or unreadable image, which can damage a monitor
very quickly.
The direction and point of contact of the electron stream on the phosphor
display are determined by deflection coils coupled with a series of magnetic
fields generated by a ring of electromagnets placed around the narrow end of
the tube. This collection is called the yoke, because it forms a yoke around the
tube. Figure 11.2 shows a cathode-ray tube.
Figure 11.2 Cathode-ray tube
NOTE
The CRT-based monitor has been around for a long time; recently,
its successor, the liquid crystal display (LCD) monitor, commonly
found on laptop computers, has started to show up on desktops
(although its high price has limited its impact on the monitor
market).
Screen Resolution and Pitch
The term resolution refers to the degree of detail offered in the presentation of
an image. The method of measurement varies, based on the medium—
photographic lenses, films, and paper are measured using lines per inch,
whereas computer monitor manufacturers express resolution in pixels per
inch. The greater the number of pixels per inch, the smaller the detail that can
be displayed and, consequently, the sharper the picture.
Monitor resolution is usually expressed as a × b where a is the number of
horizontal pixels, and b is the number of vertical pixels. For example, 640 ×
480 means that the monitor resolution is 640 pixels horizontally by 480 pixels
vertically. Modern monitors usually offer a variety of resolutions with different
refresh rates. Price and quality should be compared at the maximum for both,
along with two other factors, dot pitch and color depth (the latter is covered in
the next lesson).
Dot pitch is a term used to define the diagonal distance between the two
closest dots of the same color, usually expressed in hundredths of millimeters
(see Figure 11.3). For example, you might see .25 dot pitch. Generally
speaking, the smaller the pitch, the greater the number of dots, and the
sharper the resulting image. The values for dot pitch are generally reflected in
the monitor's price, and they are getting smaller as manufacturing technology
improves. You should match the monitor's dot pitch and maximum resolution
numbers to the needs of the customer, and install a graphics display card that
will meet or exceed them.
NOTE
Do not confuse pixels with dots. A pixel is the smallest image unit
the computer is capable of printing or displaying. It is usually the
first number given in screen resolution: horizontal pixels ×
vertical raster lines. For example, 640 × 480 is the standard VGA
resolution of 640 pixels per line, 480 lines deep.
Figure 11.3 Color dots on a monitor
Other Considerations in Choosing Monitors
Cost and Picture Area
There is a direct link between the size of the picture tube and the cost of the
monitor. The CRT is the most expensive part of the monitor. Graphical user
interface (GUI) operating systems have increased the demand for bigger
screens, to allow for more working area so that users can have more
applications open at once or more working room for graphics.
Bandwidth
When referring to computer monitors, the term bandwidth is used to denote
the greatest number of times an electron gun can be turned on and off in 1
second. Bandwidth is a key design factor because it determines the maximum
vertical refresh rate of a monitor, measured in megahertz (MHz). Higher
numbers are better. The lower the resolution, the faster the bandwidth. When
comparing products, remember to measure bandwidth at the same resolution
for each product.
Interlacing
Interlacing refreshes the monitor by painting alternate rows on the screen and
then coming back and sweeping the sets of rows that were skipped the first
time around. This increases the effective refresh rate but can lead to eye
strain. Interlacing is found on less expensive monitors, and it should be
avoided unless achieving the very lowest initial cost is the client's key concern.
Power-Saving Features
Because they are the highest consumers of electrical current in the average
PC, most new monitors provide some level of power-saving technology.
Consequently, VESA (the Video Electronics Standards Association) has
established a standard set of power economy controls to reduce power use
when the monitor is idle. These are collectively referred to as DPMS (Display
Power Management Signaling) modes.
DPMS technology uses monitors to gauge activity levels of the display. If there
is no change in the data stream from the adapter, as set in either the BIOS
(basic input/output system) or operating system controls, the monitor is
switched to inactive status. The goal is to reduce power consumption while
minimizing the amount of time required to restore the display to full intensity
when needed. The following table lists DPMS stages, arranged in order from
most to least power used.
Monitor
Status
On
Video
Signal
Sent
Yes
Monitor
Activity
Level
Amount of
Power
Saved
Recovery Time to
Normal Display
Active
None
N/A
Standby No
Inactive
Fair
Minimal
Suspend Yes
Inactive
Good
Long
Off
Inactive
Excellent
Longest (virtually the
same as full power)
No
Frequently turning a monitor on and off places stress on the components.
DPMS reduces the need to use the mechanical switch to turn the device on or
off. You should advise clients without power-saving systems in place to turn on
the display only when it is first needed and to turn it off at the end of each
workday.
DPMS can be configured in one of three ways: using hardware, software, or a
combination of both. When configuring a system for a new monitor, check the
manufacturers' manuals for recommendations on appropriate settings and
setup instructions.
Tuning the Monitor's Display
In most cases, the monitor must be adjusted for a proper picture when the
screen resolution or refresh rate is changed or a new display card is added to
the system. The following table lists typical monitor adjustments.
Vertical
height
Allows adjustment of the top and bottom of
the image. Image height changes.
Vertical
center
Allows adjustment of the location of the
image between the top and bottom of the
active viewing area.
Adjusts the center of the image (vertically)
Pincushion to eliminate or reduce bowing in or out of
the display image.
Horizontal
width
Allows adjustment of the size of the image
on the horizontal axis.
Horizontal
center
Allows the image to be horizontally centered.
Keystone
Allows adjustment of the top and bottom
edge widths so that the image is square.
Available on newer, larger monitors.
Demagnetizes the CRT to prevent an
Degaussing electron beam from bleeding over to an
adjacent dot, causing shadowing and loss of
color control.
CAUTION
When using the degaussing button, hold it down for only one or
two seconds; longer use could harm the monitor.
Some monitors offer advanced adjustment screws that allow the user, without
opening the monitor shell, to tune the settings that are usually available only
with interior controls. Adjust these tools only if you understand the process
and after you have reviewed the instructions in the product's manual. Any
internal repairs or adjustments to the monitor that require opening the shell
should be left to technicians with the appropriate tools and training.
CAUTION
Working inside a monitor is dangerous. The high voltages inside a
monitor can cause sudden death or serious injury. It's important to
realize that monitors contain their high-voltage charge even when
they're not operating or even plugged in. A monitor can hold its
charge for days. Before you can work safely inside the monitor,
such energy must be discharged. Remember that this is often best
left to someone who specializes in repairing monitors.
Monitor Maintenance
Monitor care and troubleshooting are usually simple tasks. Here are some
general guidelines to follow:
Make sure the enclosure is properly ventilated. Covering the opening on
the case can lead to overheating. Dust the unit at regular intervals.
Clean the face of the CRT gently: Follow the instructions in the product
manual. In most cases, this means dusting the glass with a clean, soft
cloth. Do not use window cleaners that contain solvents on the unit.
Make sure that all driver settings are kept within the operating guidelines
of the product. Never operate at higher resolutions or refresh rates than
those specified by the vendor, and stay within the limits of the display
adapter.
Use any automatic energy-conservation features supported by the
hardware and operating system. Employ a screen saver on older models
that lack energy-saving features. If possible, do not turn the monitor on
and off more than twice a day.
When a monitor fails to operate or produces an improper image, do the
following:
1. Check all cables, including power and display.
2. Check the front panel controls. Make any appropriate minor
adjustments that are needed.
3. Check and, if needed, reinstall the display drivers. Make sure all
settings are within the required limits. Reinstall by returning to a
plain 16-color, VGA display mode and adding resolution; then
increase the refresh rate.
4. Try another display adapter. If the problem is still unresolved, try
another computer.
5. If the monitor still shows problems, refer to a specialist for further
tests.
Lesson Summary
The following points summarize the main elements of this lesson:
The CRT is the main component of a traditional monitor.
Price, screen size, resolution, and refresh rate are primary considerations
when purchasing a monitor.
Resolution is a combination of horizontal pixels, vertical lines, and the
refresh rate.
Color depth indicates the maximum number of colors that can be shown.
The higher the refresh rate, the more subtle the display will appear to the
viewer, and the less flicker will be present.
A CRT has very high voltage and should be serviced only by trained
personnel.
3 4
Lesson 2: Flat-Panel Displays
Flat-panel displays do the same job as CRT monitors but have some
fundamental differences that make them more suitable for some environments
than others. This lesson shows how they work, their advantages and
disadvantages, and the issues involved in adding them to a PC system and
maintaining them.
After this lesson, you will be able to
Understand how flat-panel displays differ from CRT systems
Know what is required to install a flat-panel display
Estimated lesson time: 20 minutes
Flat-Panel and CRT Displays Compared
Flat-panel displays (FPDs) are thin, bright display outputs that are gaining a
foothold on desktops as a replacement for traditional CRT monitors. The most
obvious benefit is the much smaller amount of desk space required, because
there is no big case housing the electron gun, nor a heavy glass front. Because
they don't rely on transitory phosphors to create an image, they are free from
flicker (and produce no radiation). FPDs are also two to three times brighter
than CRT screens. Since the screen is flat, this means that there is no
distorted image at the edge of the viewing area, as there is with curved CRT
monitors. FPDs are generally easier on the eyes and don't require a "warm-up"
period to reach full color saturation.
With all those advantages, it would seem that only cost (they are much more
expensive than CRT solutions) keeps them from sweeping the market. Not so.
All technology has its pluses and minuses, and FPDs are no exception.
Take viewing angle, for example. If several people look at a CRT screen at
angles up to 50 degrees off the center, they will all experience the same image
—unless glare from a bright light source is reflected in someone's eyes. FPDs
have limited optimal viewing angles, usually much narrower than CRTs.
Most FPDs also lack the range of resolutions of their CRT-based kin. To drive
them, you will need a digital graphics adapter that is tuned to that FPD. The
limited choice means an upgrade will usually require the purchase of a new
card, and the cost will often be greater than a similar card for a comparable
CRT monitor. The following table highlights the differences between FPD and
CRT technology.
Type of
Display
Cost
FPD
More expensive, few
manufacturers; less
expensive to operate due to
lower power consumption
Limited selection of display
Compatibility adapters, fewer supported
resolutions
Flicker-free operation at all
resolutions; better
CRT
Wider range of vendors,
lower initial cost; high cost
to operate due to higher
electrical power demands
Wide range of display
adapters and drivers for
most popular resolutions
No fall-off of image quality
at reasonable viewing
Ergonomics
Size
Emissions
brightness and contrast at
optimal viewing angles; no
noticeable distortion at
edges
angles; wider range of
resolutions to meet user's
needs and working
conditions
Smaller "footprint" on desk,
lighter weight
Larger for given screen size,
much heaver construction
Lower radio and virtually no
magnetic emissions
Electron gun and phosphors
create both RFI (radio
frequency interference) and
radiation
How Flat Panels Work
FPDs create an image made of pixels, just like their CRT counterparts, but they
use different technology to accomplish that task. Several different types of
FPDs are available today, varying in cost, image quality, and several other
factors that affect both suitability to different computing applications and user
acceptance.
Liquid Crystal Displays
Even the most computer-illiterate individuals probably have experience with
LCD technology. It is used for a wide variety of inexpensive applications, from
digital watches to children's toys, from pagers and cell phones to ATMs. LCDs
form an image by using transparent organic polymers sandwiched between a
pair of polarizing filters, with some form of back-lighting.
The filters are set at a 90-degree angle to each other. In an uncharged state
(no current applied), the crystals are aligned so that light can pass through the
top filter. When a current is added, the crystals align to the electric field,
blocking the transmission of light. Not all LCD panels are created equal. The
greater the twist angle, the higher the contrast and the more responsive the
display is to changes in current.
Color light-emitting diode (LED) displays have three adjoining cells, each
equipped with a different color filter: one red, one blue, and one green. This
allows a display that makes use of the RGB color system.
There are several different types of LCD displays, varying in quality of output
and cost. Passive-matrix displays (PMDs) are the simplest, and they have been
used in calculators and watches since 1970. PMDs are too slow for today's
demanding multimedia PCs.
Active-matrix displays use TFTs (thin film transitors; TFT also describes this
type of display) at each pixel to control each pixel's on_off state. TFT makes up
the majority of both laptop and desktop FPDs today. The image is formed by an
array of LCDs on a wire grid. The result is a faster response than the passive
array.
Emerging Flat-Panel Technologies
Electroluminescent Displays
Electroluminescent displays (ELDs) actually emit light, rather than simply
controlling the transmission of a back-light source. The light generation comes
from phosphors layered between front and back electrodes. There are both
passive- and active-matrix variations of ELDs, much like those in LED
technology. Right now most ELD products are found in technical applications
(medical and defense) as well as ATM machines. Vendors will have to
overcome problems in the quality of color and the higher power usage of ELDs
compared to existing PC screens for these displays to gain acceptance as an
alternative to CRT or TFT products.
Plasma Display Panels
Plasma display panels (PDPs) work much like the fluorescent lights found in
most offices by energizing an inert gas. Phosphor films are used to produce a
color image. This technology is used to manufacture very large FPDs. Like
fluorescent lights, PDPs are relatively inexpensive to produce, but lower
contrast and brightness, as well as higher relative power consumption, have
thus far limited their use for PC applications.
Installing and Maintaining FPDs
In most respects there are few differences between adding and using an FPD
and adding and using a traditional CRT monitor. Add the display card to the
computer if the existing one is not compatible. Attach the cables, load the
proper driver, then make any resolution and color adjustments needed for a
proper display. Finally, adjust the brightness and contrast to comfortable
levels.
You will need a compatible display card, the appropriate cables (power and
display, usually supplied with the product), and drivers for the operating
system involved. Be sure the drivers are available for the operating system
before promising to add an FPD for a customer. Older operating systems may
never have drivers, and some versions of new operating systems may not
have enough sales in the right market segments to warrant the added cost to
the vendor.
NOTE
Due to the need for special cables, multisystem switches that allow
one display to be used with several computers may not be
compatible. You will need to take extra care to ensure that the
placement of the case and the display are within reach of the
cables. Some FPDs are designed to sit next to the computer, and a
tower case on the other side of a desk may be too far away.
There is little involved in maintaining an FPD. Wipe the screen with a dry, soft
cloth (per vendor recommendations) if the unit becomes dusty. Never use any
commercial cleansers or fluids on or near the screen. The unit should be
plugged into a properly selected and maintained UPS (uninterruptible power
supply) or surge protector to ensure a clean and safe electrical current.
Lesson Summary
The following points summarize the main elements of this lesson:
There are several types of flat-panel displays.
Price, image quality, and compatibility are all factors when considering an
FPD for a system as opposed to a CRT monitor.
Resolution ranges are not as great for FPDs compared to CRTs.
Most FPD products will require a special digital graphics adapter.
Passive FPDs are too slow for today's multimedia PC environment.
3 4
Lesson 3: Display Adapters
A monitor or FPD device is only half of a computer's display system; it must be
matched to a display adapter (also commonly referred to as a graphics
adapter, video card, or video controller). This lesson discusses the different
types of display adapters and design issues that affect quality and
performance.
After this lesson, you will be able to
Identify the different types of display adapters
Understand display memory and how it affects quality and performance
Select the right card for a monitor
Estimated lesson time: 25 minutes
Evolution of the Display Adapter
The display adapter has gone through several major evolutions as the nature
of PC computing has changed from simple word processing and number
crunching to the graphics-intensive world of Microsoft Windows and
multimedia.
The First PC Display Cards
The two "official" video cards for the early 8088-based IBM personal computers
(the PC and XT) were matched to the limited capabilities of the early monitors.
The MDA (Monochrome Display Adapter) offered a simple text-based
monochrome display. This adapter produced an 80-character-wide row of text
at a resolution of 720 × 350 pixels. Shortly after that, the CGA
(Color/Graphics Adapter) card appeared, providing up to four "colors"
(actually, just different intensities of the monitor's active color: amber, green,
or white). In four-color mode, CGA provided a resolution of 320 × 200 pixels.
Using just two colors allowed a resolution of 640 × 200 pixels.
With the release of the EGA (Enhanced Graphics Adapter) card, the IBM PC AT
became the first PC with the actual capability to use color. This adapter was an
improved version of CGA, offering a top resolution of 640 × 350 with 16 colors
in text-only mode, and 640 × 200 with two colors in graphics mode. The EGA
also ushered in the era of video conflicts. It was not fully backward-compatible
with CGA and MDA, and some programs would display improperly or even lock
up the system. The MDA, CGA, and EGA cards all shared the same connection,
a 9-pin d-shell, male fitting.
The human eye can distinguish 256 shades of gray and about 17 million
variations of color in a scene, the minimum required to produce true
photographic realism on a screen. EGA did not even come close. Its aim was to
offer the ability to incorporate color in pie charts and other forms of business
graphics. Although the first graphics programs came about to make use of the
EGA's graphics capability, serious computer graphics had to wait for better
hardware.
Memory and the Arrival of the Display Coprocessor
A brief digression to explain pixel depth and video memory demands will help
you understand what follows. Both the MDA and CGA adapters were equipped
with 256 KB of dynamic RAM (DRAM). The amount of memory on a display
card determines the amount of color and resolution that it can image and send
to the monitor. As the desire for better graphics and color displays increased,
so did the complexity of graphics cards, and with them, memory requirements
and cost.
Remember that the image on the monitor is a collection of dots called pixels.
Each image placed on the screen requires that code be placed in the adapter's
memory to describe how to draw it using those dots and their position in the
grid. The MDA cards featured a lookup table for each character. For MDA
adapters, a code number for that symbol and each position on the grid was
stored in memory, and the card had a chip set that told it how to construct
each of those items in pixels. The MDA and CGA cards each had 256 KB of
memory, just enough to map the screen at their maximum resolution. That's
why the CGA card had two different modes: the more colors were used, the
more memory was required. When it displayed four colors instead of two, the
resolution had to drop.
The MDA card was a 1-bit device. In other words, each pixel used 1 bit, valued
either 0 or 1 to represent whether a given position on the screen (a pixel) was
on or off. To represent colors or shades of gray, a card must use memory to
describe color and intensity. This attribute of the display, measured in bits, is
known as color depth. Color depth multiplied by resolution (the number of
horizontal pixels multiplied by the number of vertical rows on the screen)
determines the amount of memory needed on a given display adapter.
The adapters that followed the EGA cards to market all offered more colors
and, very quickly thereafter, higher resolution. That, in turn, required more
processing. The MDA, CGA, and EGA cards all relied on the host computer's
CPU (central processing unit). Although that was sufficient in the days before
widespread use of graphical interfaces and lots of color, with the advent of the
GUI, all that changed.
The new generation of display cards started the practice of including their own
display coprocessors. Coprocessors, which have their own memory, are tuned
to handle tasks that would usually slow down the PC, and many display cards
use bus mastering to reduce the amount of traffic on the system bus and to
speed display performance. Video coprocessing is also called hardware
acceleration. This process uses one or more techniques to speed up the
drawing of the monitor image. For example, one or more screen elements can
be described without using calculations that have to determine the placement
of every pixel on the screen.
These new graphics chips were designed to do one thing: push pixels to the
screen as efficiently as possible. At first, the cards that used them were
expensive and often prone to memory conflicts with the host CPU. Their
growing popularity led to rapid advances in design. In the mid-1990s, a new
graphics card was introduced on the market almost every day, and a new
processor almost every ten days.
Today, high-performance graphics adapters are the norm. Although there is no
longer a mad rush to market, the graphics coprocessor is a key element of fast
Windows performance. Next, we return to our review of standards and see how
the industry progressed to today's world of high-speed, full-color computing.
The Advent of Advanced Display Systems
Graphic artists, engineering designers, and users who work with photo-realistic
images needed more than a coarse, 16-color display. To tap into this market,
which was employing $40,000 workstations, PC vendors needed more powerful
display systems. IBM offered a short-lived and very complicated engineering
display adapter, the Professional Graphics Adapter (PGA). It required three ISA
(Industry Standard Architecture) slots, and provided limited three-dimensional
manipulation and 60-frames-per-second animation of a series of images. It
was also very expensive and a dismal failure in the marketplace.
One reason for the demise of the PGA was the advent of the VGA (Video
Graphics Adapter) standard. All the preceding cards were digital devices, but
the VGA produced an analog signal. That required new cards, new monitors,
and a 15-pin female connector. Developers were then able to produce cards
that provided the user with up to 262,144 colors and resolutions up to 640 ×
480.
The VGA card quickly became commonplace for a PC display system, and the
race was on to produce cards with more colors, more resolution, and additional
features. VESA agreed on a standard list of display modes that extended VGA
into the high-resolution world of color and photographic quality we know
today, known as SVGA (Super Video Graphics Array). The SVGA set
specifications for resolution, refresh rates, and color depth for compatible
adapters. On Pentium and later PCs, an SVGA adapter is the minimum
standard for display systems. The lowest resolution needed for SVGA
compatibility is 640 × 480 with 256 colors, and most modern adapters usually
go far beyond that. The other standard SVGA resolutions are 800 × 600 and
1024 × 768. High-end systems with large monitors are sold at 1600 × 1200
resolution at high refresh rates.
High Color, True Color, Photo-Realism, and Multimedia
Displays
The SVGA specification for 256 shades of gray is one of the basic SVGA
specifications for true photographic reproduction of monochrome images; it's
the number of shades that the human eye expects in a grayscale photo. Color
requires the same number of shades for each color in the image to achieve the
same level of visual realism. To get 256 shades requires an 8-bit memory
address system inside the card (28 = 256). In the early days of SVGA, vendors
worked to increase color quality without significantly increasing cost.
In color mode, an 8-bit card can't display all the colors in a full-color picture,
so a lookup table is used to figure the closest match to a hue that can't be
represented directly. Although this method isn't ideal, it was, for several years,
state of the art on desktop PCs. Then, early in the era of the 80486 processor,
came the 16-bit SVGA card, which allowed approximately 64,000 colors. More
bits require more memory, more processing requirements, a larger lookup
table, and a higher cost. These cards were designed to be used with larger
monitors, 15 to 17 inches at 800 × 600 or 1024 × 768 resolution. The new
systems were too expensive for average users, but graphics professionals and
power users generated a large enough market to fuel development.
Short-Lived Standards
During the early days of VGA and SVGA, three other graphics-card standards
were introduced by IBM for the PS/2. Although they never gained significant
market share or full support among adapter developers, they did increase the
demand for higher resolution and faster performance. The following list
highlights these three standards and their role in the evolution of PC graphics
standards:
8514/A, a 256-color competitor to VGA, with some hardware acceleration
capability, offered 640 × 480 resolution in noninterlaced mode, and 1024
× 768 resolution at 43.3 Hz in interlaced mode.
The eXtended Graphics Array (XGA) offered a resolution of 1024 × 768 in
8-bit (256-color) mode, and 640 × 480 in 16-bit mode (high color). It
came with 1 MB of memory and limited bus mastering.
XGA/2 boosted the high-color mode to 1024 × 768 and increased the
available refresh rates.
True Color Arrives
The SVGA adapters were a stepping stone; the growing popularity of Microsoft
Windows and scanners pushed the demand for cards that could deliver
photographic-quality color. In the early 1990s, several manufacturers
introduced add-on cards that could be attached to SVGA cards to deliver 16.7
million colors. Soon after, stand-alone products that offered both SVGA
resolution and true-color operation arrived. These adapters, known as truecolor or 24-bit displays, come with coprocessors and large amounts of memory.
In true-color mode, they have 256 shades (8-bit) available for each of three
colors: red, green, and blue. By mixing them, the system can display 224
colors. Eight bits are used in each of the three color channels. Some monitors
use traditional 15-pin cables, and some use BNC (bayonet-Neill-Concelman)
cables, with a separate cable for each RGB color, and one each for vertical and
horizontal synchronization. The latter are found on many high-performance
systems.
True-color cards originally sold for $3,000 or so, but within two years, prices
dropped under $800. These cards are now available for $150 or less. To add
value, the better cards now have TV output ports that send an NTSC (National
Television Standards Committee) signal that can be used to record images
from the monitor onto a VCR or TV set. Multimedia cards are equipped with a
TV tuner, letting the owner view TV programs on the monitor or watch DVD
(digital video disc) movies on a PC. The dramatic cost reduction and added
features result from the mass production of the coprocessors—which reduced
their cost to the manufacturer—along with the decreasing cost of video
memory.
Video Memory
As mentioned earlier, the amount of memory on a display adapter is a major
factor in determining the screen resolution and color depth that the card can
manage. Just as with system RAM (random access memory), the video
memory must be able to operate at a speed that can keep up with the
processor and the demands of the system clock. If the display adapter is too
slow at updating the image on the monitor, the user is left waiting or is
presented with jerky mouse movements and keystrokes that appear in delayed
bursts rather than as typed.
Fast Page DRAM
Early video cards used fast page-mode RAM (FPM RAM), a series of chips that
were basically the same as the RAM used on the early PC's motherboard. This
memory form was fine for MDA and CGA cards, and even the 8514/A, but with
the higher resolution, increasing pixel depth, and faster refresh rates of VGA
displays and beyond, vendors sought improved memory models to get
maximum performance out of their video coprocessors.
Video RAM
Enter dual-ported memory in the form of video RAM (VRAM). It can read and
write to both of its input/output (I/O) ports at the same time. It allows the
processor to talk to the system bus and the monitor simultaneously: fast, but
very expensive. VRAM showed up in the best cards, but vendors wanted a lowcost option as well. Some vendors just used FPM RAM, leaving the user to
discover that, at high resolution, the display was too slow for efficient
operation. These cards did sell well in the low-end market, as they allowed the
budget-minded user to operate in low-color modes for most tasks, switching
only to higher color depth for projects that required high-color or true-color
mode. Users who regularly worked in high-color or true-color mode often
quickly considered an upgrade.
EDO DRAM
An alternate is EDO DRAM (extended data out DRAM), which can begin reading
a new set of instructions before the preceding set of instructions has been
completed. This is a common form of system DRAM that boosts performance to
about 15 percent above conventional DRAM.
WRAM
WRAM (window random access memory, unrelated to the Microsoft operating
system) is a high-speed variant of VRAM that costs less to produce and boosts
performance by about 20 percent beyond regular VRAM. VRAM and WRAM
have become the standard memory types for high-end display adapters.
Synchronous Graphics RAM
The midrange display market makes use of synchronous graphics RAM
(SGRAM). As the name implies, it is tuned to the graphics-card market,
offering faster transfers than DRAM, but not as fast as VRAM and WRAM.
MDRAM
Multibank DRAM (MDRAM) is the final stop on our tour of memory acronyms. It
uses interleaving (the dividing of video memory into 32-KB parts that can be
accessed concurrently) to allow faster memory I/O to the system without
expensive dual porting. It is also a more efficient type of chip that is practical
to produce in sizes smaller than a full megabyte. A vendor can save money by
just buying the amount needed to actually draw the screen. This saves about
1.75 MB per card for a resolution of 1024 × 768.
The following table lists the standard memory requirements for the most
common resolutions and pixel depths used today. As stated previously, keep in
mind that the minimum amount of memory for MDRAM is usually less than for
other types of RAM. Some graphics cards offer additional memory and even
incorporate different types of RAM on the same card. In such cases, some of
the memory might be used for features other than merely imaging the picture
to be sent to the CRT in pixels.
Screen
Resolution
8-Bit (256Color)
16-Bit (65-KB
Color)
24-Bit (16.7-Million
Color)
640 × 480
512 KB
1 MB
1 MB
800 × 600
512 KB
1 MB
2 MB
1024 × 768
1 MB
2 MB
4 MB
1280 × 1024
2 MB
4 MB
4 MB
1600 × 1200
2 MB
4 MB
6 MB
Display Drivers
Text-based adapters under MS-DOS didn't need software drivers to interface
between the operating system and the image on the screen. Windows, OS/2,
and other graphics-rich environments do need drivers. In addition, controls are
needed to adjust the refresh rate, resolution, and any special features the card
offers. Display drivers, a software layer that marries the card and monitor to
the operating environment, handle these needs.
When installing a new card or operating system for a client, be sure to check
the manufacturer's Web site for the latest display drivers. You will reduce the
likelihood of problems in using the new addition, and you will find that most
new cards incorporate setup routines that can make quick work of getting a
new display running.
Lesson Summary
The following points summarize the main elements of this lesson:
Display adapters have gone through significant changes since the first PCs
entered the marketplace.
SVGA is considered the standard for applications today. The increasing
use of graphical operating systems fueled the need for bigger monitors,
higher resolutions, and more colors.
The coprocessor is a key factor in graphics-adapter performance.
24-bit cards are required to offer photo-realistic color displays.
Memory is a limiting factor in resolution and color depth.
Drivers are the link between the display hardware and the operating
system.
The type and amount of memory have a direct impact on video
performance. Less memory means fewer colors, and slower memory types
mean poorer performance.
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Lesson 4: Choosing and Troubleshooting Display
Systems
Matching the components of the display system to the needs of the computer
owner is critical to user satisfaction when upgrading or purchasing a system.
Knowledge of the basic steps in troubleshooting a display is the key to making
a quick repair when a component fails to operate properly. In this lesson, we
set out the basic steps to follow in selecting the right class of display hardware
for a client, proper care, and troubleshooting common problems.
After this lesson, you will be able to
Understand the basic criteria used to advise a customer about displaysystem options
Troubleshoot common display problems
Estimated lesson time: 10 minutes
Choosing a Display System
Helping a user choose the right display is relatively simple, despite the variety
of monitors and adapters on the market. The display is the part of the system
the user interacts with and "sees" the most, and it is a major factor in overall
performance. Within limits, the buyer needs to get the best display possible.
One major consideration is the maximum viewable area. For users who will
work in only one program at a time, or who don't need high resolution, a basic
monitor should suffice. Graphics-intensive applications and multitasking call
for larger monitors with faster refresh rates, and display cards to match.
Users who will be using graphics-intensive applications designed for drawing
and painting or for CAD (computer-aided design) and games will prefer a fast
graphics adapter, usually with VRAM or WRAM and high resolution and refresh
rates.
Multimedia systems can benefit from cards that offer TV out (usually in the
form of an RCA jack that lets the signal be displayed on a regular TV set using
the NTSC format), TV tuner, and hardware DVD acceleration.
The usual trade-offs between cost and performance apply, but less so now than
in the days of $3,000 high-end cards. Today, a user can purchase a fast, highquality adapter for $250 to $300, and an adapter of acceptable speed with
true-color display for $150 without the extras and expensive memory types.
Consider offering an FPD, especially if the customer has limited desktop space.
Remember that the FPD may require the purchase of a special display adapter.
In recommending a display system, start with your customers' needs, followed
by their preferences, and match the two as closely as possible to the available
budget. Keep in mind that the display adapter is only part of the equation.
Cost can be contained by using a smaller monitor or by accepting slower
refresh rates. Cutting the cost excessively can leave clients with a display that
does not support the tasks they perform or that might lead to user eye strain
from the flicker that occurs at slower-than-acceptable refresh rates for the
selected resolution.
Troubleshooting Display Systems
When MDA cards were standard, technicians had few problems with display
systems. If the cable was properly attached and the monitor was working, the
user got a picture. Today, the wide range of card options and the mix of
resolutions, refresh rates, and operating systems mean that users require help
with displays more often.
In spite of the increasing complexity of display systems, most problems can be
traced to a few common sources: cables improperly connected or damaged,
lack of power, improper monitor adjustment, corrupt or incorrect drivers, and
memory conflicts with other components. The following checklist can help you
troubleshoot the common display problems you are likely to encounter:
Verify that both the power and monitor-display adapter cables are
properly attached. Failure to attach them properly can lead to no picture
at all or to an erratic image with incorrect colors. If the monitor cable has
been removed and reseated, bent pins could be the problem. Make sure
power is reaching both the PC and the monitor and that they are turned
on.
Make sure that the adapter is properly seated in the expansion slot.
Boot the system. If you get an image during the power-on self test
(POST) but the computer does not load the operating system, suspect
memory or driver problems. The same is true if the system repeatedly
hangs during Windows operation. Try working in safe mode. If that
succeeds, reinstall the drivers and use Device Manager in the Control
Panel System utility to resolve any hardware or memory conflicts. (From
Start, select Settings, click Control Panel, double-click System, and then
select the Device Manager tab.)
Reset the card to the 640 × 480 resolution in 16-color VGA mode at the
60-Hz refresh rate. If the card works in normal mode, in Windows, at
these settings, but fails at higher resolution, color depth, or refresh rates,
check the drivers and the capabilities of the display components.
CAUTION
Do not exceed the approved refresh rate for a monitor, even if the
adapter can produce a higher scan of the screen. The result will be
an unstable or unreadable image, which can damage a monitor
very quickly.
If all these enumerated attempts fail, try a different display adapter or monitor
or test the hardware set on a different PC to see if one of the components has
failed and requires repair or replacement. In most cases, an out-of-warranty
card is not worth repairing; a specialist should examine a monitor that has
failed.
Lesson Summary
The following points summarize the main elements of this lesson:
Choosing a new display system or upgrading components is a matter of
matching the user's needs to the available hardware within the budget
allowed.
Price is not the sole issue when buying a display system. The quality of a
display is a major factor in the performance and usability of the
computer.
PC display problems can cause a variety of symptoms on a system, from
screen distortion to failure of the machine to boot.
Using a step-by-step approach and walking through possible problemsolution combinations offers a quick way to resolve many display-related
difficulties.
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Chapter Summary
The following points summarize the key concepts in this chapter:
Displays
The CRT is the main component of most monitors. The slender end of the
cylinder contains an electron gun, and the larger end is the display
screen.
Resolution is a measurement of the detail of images produced by the
monitor. It is measured in dots or pixels per inch.
Flat-panel displays are becoming a viable alternative to CRT monitors.
Although they offer real advantages in some applications, drawbacks
include higher price and limited resolution options.
The monitor is the primary power consumer in a computer system.
A monitor can be dangerous and should never be worked on without
being discharged first. In fact, in most cases, you should leave monitor
repair to a trained professional.
Video Cards
The video card is the interface between the expansion bus and the
monitor.
The PGA, VGA, and SVGA monitors each use a 15-pin, three-row, female
DB connector.
Coprocessors are used to speed up graphics-intensive displays.
Video Memory
The amount of video memory on a display card determines the maximum
resolution and color depth that the video card can provide.
Several types of DRAM are used for video memory; VRAM and WRAM are
used for high-performance displays.
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Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Describe the three elements that make up one dot of color.
2. What is the advantage of interlacing? Is it worth doing?
3. Should a monitor be turned on and off or left on all day?
4. What is the "standard" type of video card used with today's computers?
5. What is the formula for calculating the required memory for a monitorvideo card combination?
6. What does CRT stand for?
7. What are HRR and VRR?
8. Define resolution.
9. What is bandwidth?
10. Why is it dangerous to open the monitor's cover?
11. Name four common sources of video problems.
12. Explain one similarity and one difference between VRAM and WRAM.
13. What is a raster?
14. What type of connector is used for an SVGA monitor?
15. Explain the advantages of a TFT active-matrix display over a passivematrix display.
Answers
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Chapter 12
Printers
About This Chapter
This chapter discusses one of the most important add-ons to the typical PC
(personal computer). After monitors, printers are the second most common
output devices.
Before You Begin
It is a good idea to familiarize yourself with parallel ports, covered in Chapter
8, "Expansion Buses, Cables, and Connectors," before studying this lesson.
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Lesson 1: Printers
Printers are considered standard PC components; they are often bundled with
computers and sold to consumers as part of a complete package. The most
common add-ons, printers are manufactured in several popular forms. Like
other devices, each type has unique advantages and disadvantages. This
lesson covers all types and aspects of printers.
After this lesson, you will be able to
List the various types of printers and their advantages and disadvantages
Possess a working knowledge of laser printers
Troubleshoot printer problems
Identify the differences between parallel and serial printers
Understand expansion cards and how to use them
Estimated lesson time: 45 minutes
Printer Basics
Printers have virtually replaced the typewriter in the contemporary office. The
simplest printers are designed for the bargain-seeking home user, and the
most complex are designed for production use, producing over 80 pages per
minute and offering features like collating, stapling, and duplexing (internal
two-sided printing).
When evaluating printers, you should keep the following issues in mind:
Printer resolution. Resolution is usually measured in dots per inch (dpi).
This indicates the number of vertical and horizontal dots that can be
printed. The higher the resolution, the better the print quality.
Speed. This is usually given in pages printed per minute, where the page
consists of plain text with 5 percent of the printable page covered in ink
or toner.
Graphics and printer-language support. If the device is used to print
graphics, it should support one or more of the popular printer languages,
such as Adobe PostScript and Hewlett Packard's LaserJet Printer Control
Language (PCL).
Paper capacity. The number and type of paper trays available, the
number of pages that can be placed in them, and the size of pages that
can be printed all vary widely among printers. Some smaller units hold as
few as 10 sheets, whereas high-volume network printers hold several
reams of different sizes. Some printers can also be set to automatically
choose which tray to use based on the type of paper best suited for a job.
Duty cycle. This is the number of sheets of paper the printer is rated to
print per month. It is based on a plain-text page with 5 percent coverage
and does not include graphics.
Printer memory. Laser printers that will be used to print complex
graphics and full-color images require larger amounts of memory than
those that print simple text only. In many cases, this memory can be
added as an option.
Cost of paper. Will a printer require special paper? Some printers must
use special paper to produce high-quality (photo-quality) images or even
good text. Some paper stocks are too porous for ink-jet printers and will
cause the ink to smear or distort, causing a blurred image or text.
Cost of consumables. When comparing the cost of various printers, be
sure to calculate and compare the total cost per page for printing, rather
than just the cost of a replacement ink or toner cartridge.
Common Printer Terms
You should familiarize yourself with these basic terms used with printer
communication:
ASCII (American Standard Code for Information Interchange). A
standard code representing characters as numbers, used by most
computers and printers.
Font. A collection of characters and numbers in a given size, usually
expressed in style name and size, and expressed in points (pts.)—for
example, Times Roman 10-pt. bold (one point equals 1/72 inch).
Although many people think that bold and italic are variations of the
same font, technically they are different fonts. Some printers are sold
with limited fonts, such as bold only or no-bold varieties of the typefaces.
LPT (line print terminal) port. Term that describes parallel printer
ports on a computer.
PCL. Hewlett-Packard's printer control language for printers.
PostScript. The most common page-description language (PDL). A
method of describing the contents of a page as scalable elements, rather
than bitmapped pixels on the page. The printer is sent a plain ASCII file
containing the PostScript program; the PostScript interpreter in the
printer makes the conversion from scale to bitmap at print time.
Resolution enhancement. Technology that improves the appearance of
images and other forms of graphics by using such techniques as modifying
tonal ranges, improving halftone placement, and smoothing the jagged
edges of curves.
Portrait. The vertical orientation of printing on a piece of paper so that
the text or image is printed across the 8.5-inch width of the paper.
Landscape. The horizontal orientation of printing on a piece of paper so
that the text or image is printed across the 11-inch width of the paper.
Duplexing. The ability to print on both sides of a page. This cuts
operating costs and allows users to create two-sided documents quickly.
Printer Ports
Although some printers make use of serial, SCSI (Small Computer System
Interface), and other interfaces to communicate with a PC, most today use the
standard parallel printer port or one of its bidirectional variations. Two other
common communication methods are the USB (universal serial bus), covered
in Chapter 8, "Expansion Buses, Cables, and Connectors," and a network
interface.
The standard parallel port uses cable with a 25-pin female connector on one
end and a Centronics-compatible D-Shell fitting on the other. You simply
connect the Centronics-compatible end of the printer cable to the printer and
attach the 25-pin plug to an LPT port on the computer. Although parallel ports
are relatively trouble-free, they have some disadvantages:
The data transfer rate is 150 KB. This is slow compared to network cards
and other high-speed interfaces.
Parallel communication consumes system resources because it relies on
the PC's system bus and CPU (central processing unit) for transport and
management.
There are no standards for parallel cables or ports. Although parallel port
configurations follow a few common practices, this form of communication
remains the source of compatibility problems.
Parallel cables usually have a maximum effective length of 10 feet. This
can be extended by using a booster device, but at an added cost.
Impact Printers
In the early days of PC printing, the most commons forms of printers were dotmatrix and daisy-wheel designs. Both these designs create an impression by
striking an inked ribbon with enough force to place ink on the page. In this,
they function very much like typewriters. Except for a few special cases,
impact printers (one is shown in Figure 12.1) have been replaced by ink and
laser technology.
Figure 12.1 Impact printer
Dot-Matrix Printers
A quick trip through a consumer electronics store might lead the average
person to believe the age of the dot-matrix printer is over. The home and
home office segments of the market are now the domain of the ink-jet and
low-cost laser products. Still, in business locations, where the ability to print
several copies at once is a driving factor, the loud and lowly dot-matrix still
rules. As a result, you must understand how they work and how to maintain
them.
Dot-matrix printers form characters as raster images on paper by pressing pins
onto an inked ribbon, which then is pressed onto paper. Dot-matrix printers
use an array of pins (commonly 9 or 24 pins) that are made of stiff wire. The
higher the number of pins, the more dots per square inch and the higher the
print quality. The pins are held in a print head that travels on a rail in front of
a roller that transports the paper. The pins are controlled by electromagnets;
dots are created when power is applied to selected electromagnets in the print
head, forcing the desired pin away from a magnet in the print head. The pins
strike an inked ribbon, which then strikes the paper. A character is formed as
the individual dots are struck. Each character produced by the print head is
made up of several rows and columns of dots (see Figure 12.2). Highresolution dot-matrix printers use more dots to form one character.
Figure 12.2 Dot-matrix letters formed from dots
Maintaining a dot-matrix printer is very simple.
Change the ribbon.
Keep the printer clean.
Keep the print head clean.
Replace the print head if it fails.
Troubleshooting a dot-matrix printer usually requires a reference manual.
There are so many printers on the market that no single guide will suffice to
help a computer technician troubleshoot all printer problems. If a manual for a
particular printer is unavailable, check the printer itself for instructions
(sometimes there are diagrams inside the printer). Usually, a thorough
inspection of the mechanical parts will uncover the problem. The following
table lists common problems encountered with dot-matrix printers and possible
causes.
Symptom
Possible Cause
Printer does not
function at all.
No power is getting to printer.
Fuse is blown.
Device does not print
although power is on.
Printer is not online.
Printer is out of paper.
Printer cable is disconnected.
Printer won't go online. Printer is out of paper. (Check connections.)
Paper slips around
platen.
Paper is not being gripped properly. (Adjust
paper-feed selector for size and type of paper.)
Head moves but does
not print.
Ribbon is not installed properly or is out of ink.
Head tears paper as it
moves.
Pins are not operating properly. (Check pins; if
any are frozen, the head needs to be replaced.)
Paper bunches up
around platen.
There is no reverse tension on paper.
Paper has "dimples."
Paper is misaligned or the tractor feed wheels
are not locked in place.
Paper/Error indicator
flashes continuously.
There is an overload condition.
Printout is doublespaced or there is no
spacing between lines.
Printer configuration switch is improperly set.
(Make sure it isn't set to output a carriage
return or linefeed after each line.)
Printer cannot print
ASCII characters above
code 127.
Printer configuration switch is improperly set.
Print mode cannot be
changed.
Printer configuration switch is improperly set.
Ink-Jet Printers
Run the Inkjet video located in the Demos folder on the CD accompanying this
book to view a presentation of ink-jet printers.
Ink-jet printers have replaced dot-matrix printers in the low-end market and
thermal wax printers (not covered in the exam) in the low-end color market.
Many computer manufacturers and large computer stores offer an ink-jet
printer as part of a computer system package deal.
Ink-jet printers spray ink onto paper to form images. They produce goodquality printing and—compared to dot-matrix and wax printers—they are
relatively fast. They also require little maintenance beyond cleaning and ink
cartridge replacement. Their ability to easily produce color as well as standard
black-and-white images makes them attractive.
IMPORTANT
When installing a new ink-jet cartridge or replacing the cartridge
on an existing ink-jet printer, follow the instructions carefully! The
cartridge is not just a simple ink container. It must be properly
pressurized, and there are sensors on the unit (small metal plates)
that must line up with contacts on the cartridge transport. Read
the product manual for details.
When recommending an ink-jet printer, consider the cost of printing as well as
the cost of the printer itself. Ink-jet cartridges are usually more expensive per
page than those for a laser printer.
You might find it cost-effective to equip an office with more than one kind of
printer. Many offices have a heavy-duty, high-speed, black-and-white laser
printer for text printing, an aging dot-matrix printer for forms and labels, and
a color ink-jet printer for graphics. It is also common to find several printers
available on a local office network.
If a printer fails to operate, the first step in determining the source of the
problem is to decide if the problem lies with the printer or with the computer.
The best place to start is at the printer, with a visual inspection. Look for
simple issues, like a tray out of paper or a paper jam. Most printers have
either a light-emitting diode (LED) panel or lights that warn of common
problems.
If visual inspection of the printer does not turn up an obvious fault, proceed to
the printer's self-test program. In most cases, you can initiate this routine by
holding down a specified combination of control keys on the printer (check the
owner's manual for diagnostic procedures) while you turn it on. If a test page
prints successfully, the problem is most likely associated with the computer,
the cabling, or the network. The following table lists some typical problems
encountered with ink-jet printers and possible causes.
Symptom
Possible Cause
Power is on but
device does not
print.
Printer is not online.
Printer is out of paper.
Printer won't go
online after user
has replaced ink
cartridge.
Cartridge is installed incorrectly.
Printer cable is disconnected.
Printer is plugged
in, but all
indicator lights
are off and the
printer appears to
be dead.
Check the drive mechanisms and motors for signs of
binding. They might need to be replaced.
Fuse is blown. (Check the power supply's fuse and
replace with one of the same type and rating, if
necessary.)
Print head does
not print.
Ink reservoirs are empty. (Check the ink supply and
replace the ink cartridge, as necessary.)
Paper does not
advance.
Paper-handling hardware is jammed. (Check the
Control Panel to confirm that the printer is online. If
so, you will need to inspect the paper-handling motor
and gear train. You can do this by setting the printer
offline and pressing the form-feed button.)
Laser Printers
Run the Laser video located in the Demos folder on the CD accompanying this
book to view a presentation of laser printers.
The laser printer has become the dominant form of computer output device,
with models ranging from personal, low-volume, desktop printers to
behemoths that fill half a room and serve hundreds of users, churning out
reams of pages every day.
All laser printers follow one basic engine design, similar to the one used in
most office copiers. They are nonimpact devices that precisely place a fine
plastic powder (the toner) on paper. Although they cost more to purchase than
most ink-jet printers, they are much cheaper to operate per page, and the
"ink" is permanent. (Most ink-jet images are, at best, water-resistant.)
Primary Components of a Laser Printer
A laser printer is a combination of mechanical and electronic components.
Although the internal workings of the printer generally are not a concern for
the average PC technician, you should be familiar with the parts and processes
involved in their operation.
Paper Transport
The paper path for laser printers ranges from a simple, straight path to
complicated turns in devices with options such as duplexers, mailboxes, and
finishing tools like collators and staplers. All these devices have the same goal:
to move the paper from a supply bin to the engine where the image is laid on
the paper and fixed to it, and then to a hopper for delivery to the user. Most
printers handle a set range of paper stocks and sizes in the normal paper path,
and a more extensive range (usually heavier paper or labels) that can be sent
though a second manual feed, one sheet at a time. When users fail to follow
the guidelines for the allowed stocks, paper jams often result.
Logic Circuits
Laser printers usually have a motherboard much like that of a PC, complete
with CPU, memory, BIOS (basic input/output system), and ROM (read-only
memory) modules containing printer languages and fonts. Advanced models
often employ a hard disk drive and its controller, a network adapter, a SCSI
host adapter, and secondary cards for finishing options. When upgrading a
printer, check for any updates to the BIOS, additional memory requirements
for new options, and firmware revisions.
User Interface
The basic laser printer often offers little more than a "power on" LED and a
second light to indicate an error condition. Advanced models have LED panels
with menus, control buttons, and an array of status LEDs.
Toner and Toner Cartridges
To reduce maintenance costs, laser printers use disposable cartridges and
other parts that need periodic replacement. The primary consumable is toner,
a very fine plastic powder bonded to iron particles. The printer cartridge also
holds the toner cylinder, and often the photosensitive drum. The cartridge
requires replacement when the level of toner is too low to produce a uniform,
dark print. Some "starter" cartridges shipped with a new printer print only 750
sheets or so, whereas high-capacity units can generate 12,000 or more pages.
Keep in mind that what constitutes a "page" is based on a 5 percent coverage
area, less than a standard letter and far below that of a page of graphics or
images.
Photosensitive Drum
The photosensitive drum is a key component that is usually part of the toner
cartridge. The drum is an aluminum cylinder coated with a photosensitive
compound and electrically charged. It captures the image to be printed on the
page and also attracts the toner to be placed on the page.
IMPORTANT
The drum should not be exposed to any more light than is
absolutely necessary. Such exposure will shorten its useful life.
Keep the surface free of fingerprints, dust, and scratches. If these
are present, they will cause imperfections on any prints made with
the drum. The best way to ensure a clean drum is to install it
quickly and carefully and leave it in place until it must be replaced.
The Laser
The laser beam paints the image of the printed page on the drum. Before the
laser is fired, the entire surface of the photosensitive drum and the paper are
given an electrical charge carried by a pair of fine wires.
Primary Corona
The primary corona charges the photosensitive particles on the surface of the
drum.
Transfer Corona
The transfer corona charges the surface of the paper just before it reaches the
toner area.
Fuser Rollers
The toner must be permanently attached to the paper to make the image
permanent. The fuser rollers—a heated roller and an opposing pressure roller
—fuse toner onto the page. The heated roller employs a nonstick coating to
keep the toner from sticking to it. The occasional cycling heard in many laser
printers is generated when the fuser rollers are advanced a quarter turn or so
to avoid becoming overheated.
Erase Lamp
The erase lamp bathes the drum in light to neutralize the electrical charge on
the drum, allowing any remaining particles to be removed before the next
print is made.
Power Supply
Laser printers use a great deal of power and so should not be connected to a
UPS (uninterruptible power supply) device. The high voltage requirements of
the imaging engine and heater will often trip a UPS. In addition to the motors
and laser print heads, the printer also has a low direct current (DC) voltage
converter as part of the power package for powering its motherboard, display
panel, and other more traditional electronic components.
Drivers and Software
Most laser printers ship with a variety of software that includes the basic
drivers that communicate with the operating system, diagnostic programs, and
advanced programs that allow full control of all options and real-time status
reporting. New advances in network laser printing allow print-management
tools and printing to work over the Internet. A user can send a print job to an
Internet site or manage a remote print job using a Web browser.
The Mechanics of Laser Printing
Now that you know the major parts of the printer, here's a quick survey of
how the laser printer works and the components needed to handle each task.
(Some of these tasks occur simultaneously in actual printing.)
Communicating
The following sequence occurs as computer-to-printer communication is
established:
1. The operating system sends a request to the printer and is informed that
the printer is online and ready to accept data.
2. The PC starts sending data.
3. During the printing process, the printer—if it is able to handle
bidirectional communications—informs the computer of any problems
encountered while handling the print job so the user can address the
complaint. These messages might include an out-of-paper condition,
paper jam, or low toner.
4. After the entire job has been sent, the printer acknowledges the receipt
of all data and waits for the next request.
Many printers can store more than one job, and network printers often have
hard disk drives that can hold common jobs to allow the printer to print
without being connected to a PC.
Warming Up
The printer might delay accepting the job or printing the first page while it
warms up its rollers and the imaging drum.
Raster Image Processing
The image (text and graphics) to be made is converted into a series of raster
lines that can be drawn much the same way as the image is formed on the
PC's monitor. The data is stored in memory, waiting for the send command.
Paper Feeding
The printer moves a sheet of paper from the proper tray onto a series of
rollers, through the imaging and fixing areas, and to the output hopper.
Drum Cleaning and Charging
Any residual toner from past jobs is scraped from the printer's photosensitive
drum. A fine wire (the primary corona) produces a negative electrical charge
across the entire face of the drum. The image is set in raster lines as a series
of fine dots on the drum.
Imaging the Drum
The information from the raster image processor is read from memory and
sent to the print engine one line at a time. The laser sets a positive charge in
the areas of the image to be filled with toner.
Transferring Toner to the Drum
A film of fine plastic powder is placed on the toner transfer roller, which is
turning close to the photosensitive drum. This toner is then attracted to the
positively charged areas of the drum.
Transferring Toner to the Paper
The corona wire places a positive electrical charge on the paper as it moves
close to the drum. The toner is attracted to the page, forming an image.
Fusing the Toner
The page passes through a pair of rollers. The roller on the side toward the
toner that has been placed on the page is heated just enough to melt the
plastic toner particles onto the page without smearing. The roller on the other
side supplies the needed pressure.
Finishing and Output
After the toner has been fused to the paper, the next step is usually to
transport the page to the output tray. However, if other options—such as a
duplexer or collator—are available, the page might be routed through a
separate path, based on the options for the current print job, and then sent to
the output tray. Figure 12.3 shows the process of laser printing.
Figure 12.3 The laser printing process
Laser Printer Resolution
The quality of a laser printer is directly related to its resolution, given in dpi.
Horizontal resolution is determined by how fine a line can be focused on the
drum by the laser (the number of dpi across the page); vertical resolution is
based on the increment by which the photosensitive drum is turned for each
pass of the raster line.
In most cases, resolution is given as a single number, indicating that both the
horizontal and vertical increments are the same. The first laser printers
provided 300 dpi resolution; printers today commonly provide 600 and 1200
dpi. The higher the number, the sharper the detail and the more memory
required to image the page. In general, the human eye cannot distinguish
between 600 dpi and 1200 dpi text on bond paper, but the higher resolution
does benefit images and drawings by providing a smoother transition between
tones and curved lines.
TIP
Many laser printers offer a "toner saver" setting that uses a lowerresolution draft mode, thereby extending the life of a toner
cartridge by placing less toner on each page.
Troubleshooting Laser Printer Problems
Properly installed laser printers are quite reliable when operated and
maintained within the guidelines set by the manufacturer. Still, given the
combination of mechanical parts, the variety of steps in printing, and the
innovative ways some users use the printer, problems do occur. The following
table lists a few prob-lems that can be encountered with laser printing and
their possible causes.
Symptom
Ghost
images
appear at
regular
intervals
on the
printed
page.
Possible Cause
Photosensitive drum is not fully discharged. Previous images
used too much toner, and the supply of charged toner is
either insufficient or not adequately charged to transfer to
the drum.
Light
Previous page(s) used too much toner; therefore, the drum
ghosting
could not be properly charged for the image (called
appears on
developer starvation).
pages.
Dark
ghosting
Drum is damaged.
appears on
pages.
Page is
completely
black.
Primary corona, laser scanning module, or main central
board has failed.
Random
black spots
Drum was improperly cleaned; residual particles remain on
or streaks
drum.
appear on
page.
Marks
appear on
every
page.
Printing is
too light
Drum is damaged and must be replaced.
(appears in Toner is low.
a columnlike
streak).
Memory
overflow
error.
Not enough RAM—printing resolution too high.
Characters
Print density is incorrect. (Adjust the darkness setting on the
are
toner cartridge.)
incomplete.
Mass of
melted
plastic is
spit out.
Wrong transparency material is used (see section on
transparency, later in this lesson).
Pages are
creased.
Paper type is incorrect.
Characters
are
warped,
overprinted, or
poorly
formed.
There is a problem with the paper or other media or with the
hardware. (For media, avoid paper that is too rough or too
smooth. Paper that is too rough interferes with fusing of
characters and their definition. If the paper is too smooth, it
can feed improperly, causing distorted or overwritten
characters. For hardware, run the self-test to check for
connectivity and configuration problems.)
After
clearing a
paper jam
from the
Printer has not reset. (Open and close the cover.)
tray,
printer still
indicates a
paper jam.
Paper
continues
to jam.
Problem with the pickup area, turning area, and registration
(alignment) area. (Look for worn parts or debris.)
Ghosting
The term ghosting is used to describe unwanted images that are produced on
the printed page at regular intervals. This usually occurs when the drum is not
fully discharging or is being saturated with excess toner. One remedy is to
print one or two totally black pages; this will pull the toner off the drum and
onto the paper. If the problem persists, try using a new toner cartridge (if the
toner is part of the cartridge assembly). If those steps fail, the printer will
require servicing by a trained technician who is able to adjust the internal
settings that regulate toner levels during printing.
Printing on Transparencies
When printing on transparencies, use only materials approved for laser
printers. Laser printers generate far more heat than other types of printers,
and using the wrong material can cause serious damage.
CAUTION
Check the printer documentation before printing transparencies
with a laser printer. Unauthorized materials could melt and
damage a laser printer's internal components. Be sure that the
media is placed in the proper tray, with the proper side facing up.
A mistake here can ruin the printer!
Hardware Problems
Most laser printers offer the ability to print a page or more of diagnostic and
configuration information. If you suspect a hardware problem, print these
sheets. Check for status lights, menu warnings, or error messages. The
manual should list steps to be taken in troubleshooting common problems that
are indicated by the printer's display. The variety of error codes that exist, the
result of different options on printers, even from the same vendor, makes a
detailed listing beyond the scope of this volume and beyond the skills required
for the exam. Refer to the printer's manual for details concerning codes for a
given printer.
Lesson Summary
The following points summarize the main elements of this lesson:
The three most common printers are dot-matrix, ink-jet, and laser
printers.
Computer technicians can expect to encounter printing problems
regularly.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Printers
Most printer problems can be resolved quickly by checking for paper jams,
expended consumables, or improper use.
The key components of a laser printer are the power supply,
photosensitive drum, eraser lamp, primary corona, laser, transfer corona,
and fuser.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Name the three most common types of printers and describe their
advantages and disadvantages.
2. The dot-matrix printer is an ____________ printer. Name at least one
advantage of this type of printer. Name at least one disadvantage.
3. What are the six steps of laser printing?
4. Which components are usually included in a laser printer's replaceable
toner cartridge? Why?
5. What causes black spots to appear on a document that has been printed
on a laser printer? How can this problem be resolved?
6. In addition to the cost of the printer, what other costs should be
considered when purchasing a printer?
Answers
3 4
Chapter 13
Portable Computers
About This Chapter
Portable computers, once a novelty, are now a part of everyday business life.
Portable computers work and act just like larger systems, except they are very
compact. In this chapter, we look at those elements that make a portable
computer unique.
Before You Begin
Although there are no prerequisites for this chapter, you should be familiar
with all aspects of the hardware presented in earlier chapters.
3 4
Lesson 1: Portable Computers
Portable computers are a growing part of everyday life, both for users and
technicians. In general, the A+ technician has a very limited role in repairing
these machines. Still, you must understand how to deal with minor problems
and answer user questions about proper operation and care.
After this lesson, you will be able to
Distinguish among the different categories of portable computers
Identify the unique components of portable systems
Define the unique problems of portable systems
Distinguish among the different types of computer cards designed for
portable computers
Estimated lesson time: 50 minutes
The category of portable computers includes laptop, notebook, and
subnotebook (palmtop) computers, as well as the newest categories, PDA
(personal digital assistant) and handheld computers.
Types of Portables
Portable computers are classified according to size and function. Today there
are three basic types of portable computers: laptops, notebooks, and
subnotebooks.
The first "portable" computers were often called "luggables." The size of a
portable sewing machine, they tipped the scales at 30 pounds. Equipped with a
small CRT (cathode-ray tube) display, they were actually a traditional PC in a
slightly smaller case.
The real change in portable computers came with the advent of the flat-panel
display, allowing the portable to take on the now-familiar slim design. Laptop
is the term used for the heavier version, usually offering most of the features
of a full-fledged PC but with a folding flat-panel display and integrated
keyboard. Notebooks are slender devices that often lack the full range of
storage as part of the normal configuration. PDAs, a special group of products
offering a subset of features including e-mail, schedule tracking, contact
records, and limited note taking and Web browsing, are beyond the scope of
this chapter.
Laptop Computers
With advancements in battery technology and the advent of functional, largescreen, liquid crystal displays (LCDs), the first truly portable computers,
referred to as laptops, were produced in the late 1980s. These units featured
integrated AT-compatible computer boards, including I/O (input/output) and
video controller functions. Laptops, as mentioned, usually feature a folding
LCD display and a built-in keyboard and pointing device. They also use an
external power supply and a removable, rechargeable battery. Today's laptops
have fairly large (2 GB or more) hard drives, a CD-ROM drive (or DVD drive),
and a floppy disk drive (often the latter two are interchangeable plug-ins).
When laptops originally appeared on the market, they were the smallest
portable computers made. Today, they are high-end machines that offer
features and performance comparable to a desktop system.
Notebook Computers
Advances in integrated circuit (IC) technology allowed the size of computer
components to be reduced even further, and, in the early to mid-1980s, the
notebook computer was born. Notebooks are roughly 8.75 inches deep × 11
inches wide × 2.25 inches thick, and designers are working to decrease the
size and power consumption of these units even further. The reduction in size
comes at a cost, however, and notebooks typically have smaller and less
capable displays and keyboards than laptops. A wide variety of specialty items
have appeared on the market designed to overcome some of the notebook's
shortcomings. Docking ports are one such item.
Docking Ports
Docking ports (also known as docking stations) are specialized cases into which
an entire notebook computer can be inserted. This allows the notebook to be
connected to desktop I/O devices such as full-sized keyboards, CRT monitors,
and network connections. At minimum, a docking station provides an
alternating current (AC) power source for the notebook. Docking stations are
highly proprietary items designed for use with specific computer models. They
are handy for the user who wants to maintain only one computer system and
avoid the necessity of transferring information between two systems. With a
docking port and a well-equipped notebook computer, it is possible to have the
best of both worlds.
It is not necessary to have a docking port to use a portable computer with a
full-sized keyboard, pointing device, and monitor. Most portables have
standard connectors for these peripherals. However, be aware that you might
have to connect the devices before booting up the computer.
Subnotebook (Palmtop) Computers
Even smaller than the notebook computers are subnotebook computers, also
known as palmtops or handhelds. These tiny systems are 7 inches wide × 4
inches deep × 1 inch high. Due to their size, they are rather limited in
function. Keyboards, for example, are too small to permit touch-typing. With
notebooks decreasing in cost and weight, palmtops have been losing market
share and popularity.
Computer Cards
To provide laptop and notebook computers with the same expandability
associated with desktop computers, the PCMCIA (Personal Computer Memory
Card International Association) established several standards for credit-cardsized expansion boards that fit into small slots on these smaller machines.
These expansion boards are now commonly referred to as PC Cards. The
PCMCIA standards have revolutionized mobile personal computers, providing
them with the ability to add memory expansion cards, network interface cards
(NICs), SCSI (Small Computer System Interface) devices, communication
hardware (for instance, modems and faxes), and many other devices that were
previously unavailable to laptop and notebook computer users.
Compatibility problems surfaced along with the development of the PC Card for
portable computers. To overcome these incompatibilities, PCMCIA standards
were created. The following table outlines the four PCMCIA types and their
guidelines.
Type
Standard Description
This original computer-card standard is now referred to as the
Type
Type I standard. These slots work only with memory expansion
I
cards. Type I cards are 3.3 mm thick.
Type II cards support most types of expansion devices (like
Type
communication hardware) or network adapters. Type II can
II
accommodate cards that are 5 mm thick.
Type III slots are primarily for computers with removable hard disk
Type
drives. This standard was introduced in 1992. They are 10.5 mm
III
thick; however, they are compatible with Type I and Type II cards.
Type Type IV slots are intended to be used with hard disk drives that
IV
are thicker than the 10.5 mm Type III slot.
The PC Card itself is usually sealed in a thin metal case. One end contains the
interface to the PC Card adapter (68 tiny pinholes); the other end might
contain a connector for a telephone line, a network, or another external
device.
PC Card is part of the Plug and Play standard, which means it allows you to
add components without first shutting off or rebooting the computer. In short,
PC Cards are not configured with jumper settings (because they don't have
any) but with software.
Portable Computer Hardware
Although many components in a portable computer are similar to those of a
desktop system, some components are very different. The major difference
between a portable system and desktop system is the display screen.
Displays
Portable computers have a flat LCD screen that is about .5 inch thick. The
display is typically the most expensive component in a portable system. Often
it is more economical to replace the entire computer than to replace the
screen. An LCD display is designed to operate at a specific resolution because
the size of the pixels on an LCD panel cannot be changed. On a desktop
system, by contrast, the signal output from the video adapter can change the
resolution on the monitor, thereby changing the number of pixels on the
screen. An LCD panel should be thought of as a grid ruled to a specific
resolution. Transistors control the color that is displayed by each pixel. The
two major types of LCD displays used in portable systems today (dual-scan and
active-matrix) are defined by their arrangement of transistors.
Dual-Scan Displays
The dual-scan display (also known as a passive-matrix display) consists of
transistors running down the x- and y-axis of the screen. The number of
transistors determines the screen's resolution. The two transistors that
intersect on the x- and y-axis control each pixel on the screen.
If a transistor fails, the entire line of pixels is disabled, leaving a black line
across the screen. There is no way to repair this problem except to replace the
display. The term dual-scan is derived from the fact that the processor redraws
half of the screen at a time, which speeds up the refresh rate a little.
Dual-scan displays are considered inferior to active-matrix screens because
they tend to be dimmer. For this reason, portable computers with this
technology are becoming rare. They work by modifying the properties of
reflected light rather than generating their own light. They are also more
prone to ghost images, and it is difficult for two people to see the screen at the
same time, because these displays can't be viewed well from an angle. The
standard size for this type of screen is 10.5 inches (measured diagonally) with
a resolution of 640 × 480. New systems are available with 12.1-inch and
larger displays that have a resolution of 800 × 600.
Active-Matrix Displays
Active-matrix displays are also known as TFTs (thin film transistors). They
differ from dual-scan screens because they have a transistor for every pixel on
the screen rather than just at the edges. Electrodes apply voltages at the
perimeter of the grid to address each pixel individually.
Because each pixel is powered individually, generating its own light and the
appropriate color, a much brighter and more vivid picture results. Creating
light instead of altering reflection provides a wider viewing angle, which allows
more than one viewer to see the screen at a time. The refreshes are faster and
the display lacks the fuzziness associated with the dual-scan systems.
Naturally, the cost of having 480,000 transistors instead of merely 1400 (on
an 800 × 600 screen) makes the active-matrix screen more expensive. It also
requires a lot more power and drains batteries faster. Failure of a transistor
causes individual "dead pixels," but this is far less noticeable than the black
line caused by a transistor failure of the dual-scan screen.
Larger screens and higher resolutions mimicking that of desktop models have
become the standard on high-end laptops. Many portable systems today also
include PCI (Peripheral Component Interconnect) bus video adapters. These
screens come very close to the quality of a desktop display, but lack some of
the fine controls available on fixed units.
Screen Resolution
An LCD display's resolution is determined as much by the screen hardware as
by the drivers and amount of installed video memory. Some machines with
less robust screens achieve resolutions of 1024 × 600 (and even more) by
using a virtual screen. This is a memory-swapping technique whereby a larger
display is held in video memory while the actual screen displays the portion
that fits into a 640 × 480 window. The cursor can be used to "pan" the image
so that the viewable desktop is within the physical limits of the actual display.
As in regular desktop systems, color depth is affected by video memory. To
operate any LCD display in 16-bit or 24-bit color mode, you must have
sufficient video memory available. Portables usually have video adapter
hardware permanently installed on the motherboard, which makes an upgrade
of the display features virtually impossible. Most portables allow connection to
an external monitor to increase video capabilities.
NOTE
LCD technology is not limited to portables. Large, flat-panel LCDtype displays are now available for desktop computers, although
they are quite expensive. (See Chapter 11, "The Display System,"
for more information.)
Processors
Computer CPU (central processing unit) manufacturers spend a great deal of
time and effort on designing chips specifically for the portable market. In
desktop systems, cooling fans housed inside the case dissipate CPU heat. There
is no room for this solution in a portable system, so manufacturers have
addressed this problem in the packaging of the chip itself.
Chip manufacturer Intel's solution to the size and heat problems is the Tape
Carrier Package. This method of packaging reduces the size, power
consumption, and heat generated by the chip. A Pentium mounted on a
motherboard using Tape Carrier Packaging is much smaller and lighter than
the pin grid array (PGA) used in desktop systems. The 49-mm square of the
PGA is reduced to 29 mm, the thickness to approximately 1 mm, and the
weight from 55 grams to less than 1 gram.
The Tape Carrier Packaging processor is bonded to a piece of polyamide film,
which is like photographic film, using tape automated bonding (TAB). This is
the same process used to attach electrical connections to LCD panels. The film
(called tape) is laminated with copper foil etched to form the leads that
connect the processor to the motherboard. When the leads are formed, they
are gold-plated to protect them against corrosion, bonded to the processor chip
itself, and then the entire assembly is coated with a protective resin.
After being tested, the tape is cut to the proper size and the ends are folded
into a "gull wing" shape that allows the leads to be soldered to the
motherboard while the processor is suspended slightly above it. A thermally
conductive paste is inserted between the processor chip and the motherboard,
allowing heat to be dissipated through a sink on the underside of the
motherboard, keeping it away from the soldered connections. Of course,
because Tape Carrier Packaging processors are soldered to the motherboard,
they usually cannot be upgraded.
Some manufacturers use standard PGA processors, sometimes accompanied by
fans. In addition to having a greatly reduced battery life, these systems can be
too hot to touch comfortably. Always check the exact model of processor that
is used in a system you intend to purchase, not just the processing speed. You
might not want to purchase a non-Tape Carrier Packaging processor for the
aforementioned reasons.
Voltage Reduction
Mobile Pentiums have operated at 3.3 volts from the days of the original 75MHz chip, but the newer and faster models have reduced the voltage to only
2.9 volts for internal operations, retaining the 3.3-volt interface with the
motherboard. This translates into a processor that uses as little as 60 percent
of the power of a desktop system.
Memory
As with desktop systems, adding memory is one of the most common upgrades
to portable computers. Unlike desktop computers, which offer only three basic
types of slots for additional RAM (random access memory), there are dozens of
different memory-chip configurations designed to squeeze memory upgrades
into the small cases of portable systems.
Some portables use memory cartridges that look a lot like PC Cards, but they
plug into a dedicated IC memory socket. Others use extender boards like
SIMMs (single inline memory modules) and DIMMs (dual inline memory
modules). In any case, it is strongly recommended that you only install
memory modules that have been designed for your system, and only in the
configurations recommended by the manufacturer. This does not necessarily
limit you to products made by your system's manufacturer, however, because
a number of companies manufacture upgrade modules for dozens of systems.
Portable computers use the same types of dynamic RAM (DRAM) and static
RAM (SRAM) as desktops and, thanks to advances in thermal management,
today's high-end portable systems usually include SRAM cache memory.
Hard Disk Drives
Except for its size and packaging, portable hard disk drive technology is similar
to desktops. EIDE (Enhanced Integrated Drive Electronics) drives are standard
in portable computers with the exception of the Macintosh computer, which
uses SCSI. Internal hard drives, depending on the size of the system, are
typically 12.5 mm or 19 mm tall, and use 2.5-inch platters. As with memory
modules, hard drives are also mounted in the system a little differently by
manufacturers; this can cause upgrade compatibility problems.
Some manufacturers use a caddy to hold the drive and make connections to
the system. This makes upgrading as simple as inserting a new hard disk drive
into the caddy and then mounting it in the system. Other systems require
purchase of a specifically designed drive, complete with the proper connections
built into it. Replacing the hard drive can be much easier in many portable
systems than in their desktop counterparts.
The result is that multiple users can share a single machine by simply
snapping in their own hard drives. However, because laptops are specialized
equipment, any servicing beyond batteries, hard drives, and memory is usually
left to specialists or the manufacturer.
The support provided by the system's BIOS (basic input/output system)
determines the upgradability of a system. Older systems, particularly those
manufactured before 1995, might offer only limited drive-size options. BIOS
chips made before EIDE hard disk drives became the standard can support a
maximum hard drive size of 528 MB. A flash BIOS upgrade might be available
for your system to provide additional drives. Another option for expanding
hard drive space is the PC Card hard drive. This device fits into a Type III PC
Card slot and can provide as much as 1-2 GB of additional space. External
drives are also available and can be connected using a PC Card SCSI host or
specialized parallel port drive interfaces—you can use any size SCSI drive you
choose without being limited by your system's BIOS.
Removable Media
Portable systems are now equipped with other types of storage media that can
provide access to large amounts of data. CD-ROM and Zip drives are now
available, as well as standard floppy disk drives. Just as in desktop
counterparts, CD-ROM is becoming standard on portables.
The swappable drive bay is increasing in popularity. This product allows the
user to switch one of several types of components in the unit. For example,
you might not need a floppy disk drive when traveling, so you can insert an
extra battery.
Keyboards
Portable keyboards are integrated into the one-piece unit and are therefore
very difficult to repair or replace. Unfortunately, the keypad is almost always
the first component to fail in a portable. The functionality and durability of the
keyboard should be an important concern when purchasing a portable system.
Today's portable keyboards are approaching the size and functionality of
desktop systems, thanks to the larger screens found on most systems. This has
created more space for manufacturers to utilize in the overall design.
Pointing Devices
Today's portable computers come with built-in pointing devices. Most of these
pointing devices are one of three types: trackball, trackpoint, or trackpad.
Trackball. This small ball (approximately .5 inch in diameter) is partially
embedded in the keyboard below the spacebar. The user's fingers
manipulate the ball. These devices are accurate and serviceable, but they
are unpopular because of their tendency to gather dirt and dust, which
dramatically reduces performance.
Trackpoint. IBM developed the trackpoint, which many manufacturers
install in their systems. It is a small, rubberized button (approximately
.25 inch in diameter) located above B and below G and H on the
keyboard. The user nudges it in any direction (rather like a tiny version
of a joystick) to move the cursor around the screen. It is convenient
because the user's hands don't need to leave the keyboard to manipulate
the trackpoint.
Trackpad. The trackpad (also known as the touchpad) is the most recent
development of the three. It is an electromagnetically sensitive pad
measuring about 1 inch × 2 inches located in the keyboard below the
spacebar. It responds to the movement of a finger across its surface to
move the cursor. Tapping the pad simulates mouse clicks (although
buttons are also provided). It is a truly innovative device, but does tend
to be overly sensitive to accidental touches and taps. It is also sensitive to
humidity, so moist fingers can cause unpredictable performance.
USB Ports
The addition of USB (universal serial bus) technology to portables has made it
much easier to add new devices or share them with other computers, like the
owner's desktop machine. The hot-swap capability, coupled with the wide
range of products (from printers and scanners to Zip drives and modems),
makes this a must-have for any new portable. Keep in mind that there are
PCMCIA USB cards on the market that can add the functionality to older
machines as well. (See Chapter 8, "Expansion Buses, Cables, and Connectors,"
for more information.)
Batteries
A great deal of technology has been developed to extend battery life and
improve power management in portable systems. However, battery life is still
one of the most significant complaints about portable systems. Even though
power management and batteries themselves have improved dramatically over
the last few years, the power needed to run faster processors and external
devices has increased, leaving battery life about the same. Actual battery life
depends as much on how the computer is used as it does on powermanagement technology. Simply put, the more you ask the computer to do,
the shorter the battery life. Today, battery life is still an issue with portable
system users. Most systems use one of three types of batteries.
Nickel Cadmium Batteries
The oldest of the three technologies, nickel cadmium (NiCad) batteries are
rarely used today. They have a short life and are sensitive to improper
charging and discharging. After being charged, NiCad batteries hold a charge
very well. How-ever, their life can be severely shortened if they are not fully
discharged before recharging or if they are overcharged.
Nickel Metal Hydride Batteries
Nickel metal hydride (NiMH) batteries have a longer life than NiCad batteries
(about 50 percent longer) and are less sensitive to improper charging and
discharging. They are also more expensive than NiCad batteries and don't hold
a charge as well when not used. They usually cannot be recharged as many
times. They are, however, used in most portable systems, especially those at
the lower end of the market.
Lithium Ion Batteries
Lithium ion batteries cannot be overcharged, hold a charge well when not in
use, and last longer than the other two types of batteries. They are also
proficient at handling the heavy-duty power requirements of today's higherend portables. Because they are the most expensive of the three battery
technologies, lithium ion batteries are usually found only in high-end systems.
Unfortunately, these batteries can be used only in systems specifically
designed for them.
CAUTION
Never install a lithium ion battery in a system designed for a
NiCad or NiMH battery. Doing so could result in a fire.
Buying a system with a lithium ion battery does not necessarily ensure a
longer battery life. Some manufacturers take the opportunity to make the
battery smaller because it is more powerful, thereby saving some space inside
the computer while delivering the same performance as a NiCad or NiMH
battery.
New Technology
Battery technology has trailed behind nearly all the other advances of the
portable system. A battery life of two hours is considered very good even when
a system's power-saving features are utilized. Some manufacturers are
designing systems that hold two batteries to try to overcome this limitation.
A fourth type of battery technology—the lithium polymer—has been in
development for several years, but it has not yet appeared on the market.
Lithium polymer batteries can be formed into thin, flat sheets and installed
behind the LCD panel. They provide approximately 40 percent more battery
life while adding far less weight to the system.
TIP
All battery types function best if they are completely discharged
before recharging. Even lithium ion batteries perform better and
last longer if they are discharged before being recharged. You can
also store charged batteries in the refrigerator to help them
maintain their charges longer.
Proper Battery Disposal
Many people give no thought to discarding exhausted batteries in the nearest
trash container, but you should take a more professional approach. Batteries
contain hazardous and environmentally detrimental materials. Be sure and
check your company policy and recommendations from the manufacturer
before disposing of any battery. Failure to do so is both poor practice and an
invitation for a fine.
Power Management
Some components in a computer system do not need to run continuously. The
purpose of power management is to conserve battery life by shutting down
these components when they're not needed.
Most portable computers include power-saver modes that suspend system
operations when the computers are not in use. Different manufacturers have
different names for their power-saver modes such as suspend, hibernate, or
conserve, but they all usually refer to two different states of power
conservation: One state continues to power the system's RAM, and the other
does not.
Generally, the suspend mode virtually shuts down the entire system after a
certain period of inactivity. However, power continues to be supplied to RAM,
and the system can be reawakened almost immediately.
The hibernate mode writes the entire contents of memory into a special swap
file and then shuts down the system. When reactivated, the file is read back to
memory. The hibernate mode takes a little longer to reactivate than the
suspend mode, but it conserves more battery life. In some systems, the swap
file used for the hibernate mode is located in a special partition of the hard
drive. If it is inadvertently destroyed, it might require a special utility from the
manufacturer to re-create it.
A document jointly developed by Intel and Microsoft, the Advanced Power
Management (APM) standard, has been, for the most part, responsible for
defining the interface (interaction) between the power-management policy
driver and the operating system. This interface is usually implemented in the
system BIOS.
Another standard currently under development by Intel, Microsoft, and Toshiba
is called the Advanced Configuration and Power Interface (ACPI). This standard
is designed to place the power-management functions under the control of the
operating system. As power-management techniques develop, it becomes
difficult for the BIOS to maintain the complex information states needed to run
the more advanced functions. Placing power management under the control of
the operating system allows applications to interact with the operating system
to let it know which of its activities are crucial and which can wait until the
next time the hard disk drive is activated.
Lesson Summary
The following points summarize the main elements of this lesson:
Portable computers are classified as laptops, notebooks, or palmtops.
PC Cards provide expandability to portable computers.
Type I PC Cards are used for memory; they are 3.3 mm thick.
Type II PC Cards are used for expansion devices; they are 5.0 mm thick.
Type III PC Cards are used for hard drives; they are 10.5 mm thick.
Display screens for portable computers are either dual-scan or activematrix.
Tape Carrier Packaging is used to make processors consume less energy
and put out less heat.
Good power management is the key to long battery life in a portable
computer.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Early "portable" computers were heavy and usually more worthy of the
term "luggable."
Today's laptops and notebooks have most of the features of a desktop
machine in a very compact package—but at a much higher cost.
A computer technician should know the four types of PC Cards and their
uses.
Batteries and power management are key factors to consider when
maintaining portable computers.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Name the three main types of portable computers.
2. What is a docking station?
3. What is the purpose of PC Cards?
4. Describe the different PC Card types.
5. How do you configure a computer card?
6. What are the two kinds of displays found on laptop computers?
7. Why is heat dissipation a concern in computer-chip technologies for
portable computers?
8. With the exception of Macintosh, what drives are standard in a portable
computer?
Answers
3 4
Chapter 14
Connectivity and Networking
About This Chapter
The ability to expand beyond the limit of a single computer in a single office
has extended the reach of the PC to global proportions. Two technologies have
driven this expansion: computer networking and the global network known as
the Internet. While we cover modems and simple Internet connections in
Chapter 15, "Telecommunications and the Internet," some of the basic
concepts of Internet addressing are covered in this chapter. (The Internet uses
the same protocol as many PC LANs.)
Before You Begin
Although there are no prerequisites for this chapter, you should be familiar
with all aspects of the hardware presented in earlier chapters.
3 4
Lesson 1: Networks
A network is defined as two or more computers linked together for the purpose
of communicating and sharing information and other resources. Most networks
are constructed around a cable connection that links the computers. This
connection permits the computers to talk (and listen) through a wire. More
recently, a number of wireless solutions have become available. Infrared ports,
Bluetooth radio links, and other protocols allow a variety of new devices to link
with PCs.
After this lesson, you will be able to
Define basic networking concepts and describe how a network functions
Configure and change network interface cards
Define basic Internet terms
Estimated lesson time: 40 minutes
Basic Requirements of a Network
In order for a network to function, three basic requirements must be met: The
network must provide connections, communications, and services.
Connections
Connections include the hardware (physical components) required to hook up
a computer to the network. Two terms are important to network connections:
The network medium. The network hardware that physically connects
one computer to another. This is the cable between the computers or a
wireless connection.
The network interface. The hardware that attaches a computer to the
network medium and acts as an interpreter between the computer and
the network. Attaching a computer to a network requires an add-in board
known as a network interface card (NIC).
Communications
Communications establish the rules concerning how computers talk and
understand each other. Because computers often run different software, to
communicate with each other they must speak a shared language. Without
shared communications, computers cannot exchange information, and they
remain isolated.
Services
A service defines those things a computer shares with the rest of the network.
For example, a computer can share a printer or specific directories or files.
Unless computers on the network are capable of sharing resources, they
remain isolated, even though physically connected.
Networking
Next we look at how the basic elements of connections, communications, and
services work together to make networks function properly.
The connections must operate so that any computer can send or receive
electrical signals (data) across the physical media that link them.
Communications must function so that when one computer sends a
message, the receiving computer can listen and understand the message.
Computers on a network must either provide a service to other computers
or make use of a service provided by other computers.
Local Area Networks
A LAN (local area network) is a network that covers a limited distance (usually
a single site or facility) and allows sharing of information and resources. A LAN
can be as simple as two connected computers or as complicated as a large site
connecting many computers. This type of network is very popular because it
allows individual computers to provide processing power and utilize their own
memory, while programs and data can be stored on any computer in the
network. Some older LANs also include configurations that rely totally on the
power of a mini- or mainframe computer (a server) to do all the work. In this
case, the workstations are no more than "dumb" terminals (a keyboard and a
monitor). With the increased power of today's PC, these types of networks are
rare.
The primary benefit of a LAN is its ability to share. The following table lists
some of the benefits of sharing the most common resources on a LAN.
Resource
Data
Benefit
The sharing of data files that reside in a common location
makes multiple-user access easier. Also, it's much easier to
maintain data integrity when there is a single, central
database. Large customer databases and accounting data are
ideal for a LAN system.
Sharing printers, for example, allows more than one user to
send jobs to a single printer. This is useful when there is
only one high-quality printer in an office and the entire office
needs to use it. It also allows one user to access multiple
Peripherals
printers, providing cost savings in hardware and redundant
resources in case one device fails. Other low-usage
peripherals, such as scanners and plotters, will be better
utilized.
Software
Sharing a single copy of an application can be cost-effective
(many software manufacturers provide site licenses—licenses
for multiple users on a server). It also allows easier
maintenance and upgrading.
Storage
Larger, faster disk systems can be used cost-effectively for
easy backups.
In addition to the ability to share resources, LANs offer many other benefits
that include:
Resilience. Regular backups of the entire system greatly reduce the risk
of data loss. Copying data to backup servers allows network operations to
continue in the event of a primary server failure.
Communication gateways. Low-cost access to fax and Internet
connections.
Electronic mail. Cost-effective and convenient communication
throughout the network.
Wide Area Networks
A wide area network (WAN) spans relatively large geographical areas.
Connections for these sites require the use of ordinary telephone lines, T1
lines, ISDN (Integrated Services Digital Network) lines, radio waves, cable, or
satellite links. WANs can be accessed through dial-up connections, using a
modem or leased-line direct connection. The leased-line method is more
expensive but can be cost-effective for transmission of high volumes of data.
Types of Networks
There are essentially two types of networks that differ in how information is
stored, how security is handled, and how the computers on the network
interact.
In a peer-to-peer network, each computer acts as either a server (sharing its
data or services with other computers) or a client (using data or services on
another computer), depending on the user's needs. Each user or workstation
establishes its own security and determines which resources are available to
other users. Typically these networks are limited in size (15–20 workstations).
Microsoft Windows for Workgroups, Windows 95, Windows 98, Windows Me,
Windows NT Workstation, Windows 2000, Novell's NetWare, UNIX, and Linux
are some software packages available for peer-to-peer networking.
A server network requires a central server (dedicated computer) to manage
access to all shared files and peripherals. This is a secure environment suitable
for most organizations. In this case, the server computer that runs the
network operating system (NOS) manages security and administers access to
resources. The client computer connects to the network and uses the available
resources. Among the most common server operating systems are Microsoft's
Windows NT Server 4, Windows 2000 Server, and Novell's NetWare. Prior to
the release of Windows NT, most dedicated servers worked only as hosts.
Windows NT allows the server to operate as an individual workstation as well.
More than one server can provide services on the network, but only one can
be responsible for the security and overall operation of the network.
Network Topology
LAN design is called topology, which describes the appearance or layout of a
network and how data flows through the network. There are three basic types
of topologies: star, bus, and ring. In the real world, you are likely to encounter
some hybrid combinations of these topologies, but for the A+ exam, we focus
only on these three.
NOTE
The illustrations that follow should not be used as exact wiring
diagrams but as sample network designs.
Star Topology
In a star network (see Figure 14.1), all devices are connected to a central
point called a hub. These hubs collect and distribute the flow of data within the
network. Signals from the sending computer go to the hub and are then
transmitted to all computers on the network. Large networks can feature
several hubs. A star network is easy to troubleshoot because all information
goes through the hub, making it easier to isolate problems.
Figure 14.1 Star topology
Bus Topology
In a bus network (see Figure 14.2), all devices are connected to a single linear
cable called a trunk (also known as a backbone or segment). Both ends of the
cable must be terminated (like a SCSI [Small Computer System Interface]
bus) to stop the signal from bouncing. Because a bus network does not have a
central point, it is more difficult to troubleshoot than a star network. A break
or problem at any point along the bus can cause the entire network to go
down.
NOTE
A bus network is often referred to as an Ethernet network.
Figure 14.2 Bus topology
Ring Topology
In a ring network (see Figure 14.3), all workstations and servers are
connected in a closed loop. There are no terminating ends; therefore, if one
computer fails, the entire network will go down. Each computer in the network
acts like a repeater and boosts the signal before sending it to the next station.
This type of network transmits data by passing a "token" around the network.
If the token is free of data, a computer waiting to send data grabs it, attaches
the data and the electronic address to the token, and sends it on its way.
When the token reaches its destination computer, the data is removed and the
token is sent on.
NOTE
This type of network is commonly called a token ring network.
Figure 14.3 Ring topology
Network Operating System
The NOS consists of a family of programs that run in networked computers.
Some programs provide the ability to share files, printers, and other devices
across the network. As previously mentioned, computers that share their
resources are called servers; computers that use the resources on other
computers are called clients. It is common to run client and server software on
the same computer. This enables you to access the resources on another
computer while coworkers make use of resources on your computer.
Networking software can be a special program added on to the computer, such
as Artisoft's LANtastic or Novell's NetWare, or it can be an integral part of an
operating system such as Microsoft's Windows 95, Windows 98, Windows Me,
Windows NT, or Windows 2000.
Network Interface Cards
NICs link a computer to the network cable system. They provide the physical
connection between the computer's expansion bus and the network cabling.
The low-powered digital signals that transmit data inside a computer are not
powerful enough to travel long distances. An NIC boosts these signals so they
can cross a network cable. The interface card also must change the form of
data from a wide parallel stream—coming in 8, 16, or 32 bits at a time—to a
narrow stream, moving 1 bit at a time in and out of the network port (parallel
to serial conversion; see Chapter 12, "Printers").
The NIC takes data from the computer, packages the data for transmission,
and acts as a gatekeeper to control access to the shared network cable.
Because the NIC functions as an interface between the computer and the
network cabling, it must serve two masters. Inside the computer, it moves
data to and from RAM (random access memory). Outside the computer, it
controls the flow of data in and out of the network cable system. Because the
computer is typically much faster than the network, the NIC must buffer the
data between the computer and cable. This means it must temporarily store
the data coming from the computer until it can place it on the network.
Installation of the NIC (see Figure 14.4) is the same as for any other
expansion card. It requires setup of the system resources: IRQ (interrupt
request), address, and software. Most cards today allow connection for either
thin Ethernet or UTP (unshielded twisted-pair) cabling. Thin Ethernet uses a
round BNC (bayonet-Neill-Concelman) connector, and UTP uses an RJ-45
connector (similar to a telephone jack).
Figure 14.4 Network interface card
Installing an NIC is just like installing any other expansion card. If you are
installing a Windows 95-compliant Plug and Play card in a Windows 95 or
Windows 98 machine, you'll simply need to physically install the card and boot
up the computer. The card will be detected and, more than likely, install itself.
You might only need to answer a few questions along the way. It requires a
little more work to install an NIC in an operating system that is not Plug and
Play-compliant. Installing network cards includes the following steps.
1. Be sure to document any changes that you make to the existing
computer. This will eliminate any confusion in the installation process and
provide future reference in case of problems.
2. Determine whether the card needs IRQ, direct memory access (DMA), or
address settings. Remember that you might have to configure these
manually, so be sure to check the card's documentation for default
settings and instructions for how to make any required changes.
3. Determine whether the necessary settings are available on the machine
on which they will be installed. If proper documentation is not available,
use diagnostic software such as Microsoft Diagnostics (MSD) to determine
settings. Check your AUTOEXEC.BAT, CONFIG.SYS, and SYSTEM.INI files;
they might give clues about which settings are already in use.
4. Turn off the machine and remove the cover. Be sure to take all
appropriate measures for protection against electrostatic discharge (ESD).
5. Set the NIC's jumpers or DIP (dual inline package) switches as necessary
and insert the card.
6. Turn on the machine and run the setup utility provided by the
manufacturer. If you are using Windows 95, Windows 98, Windows Me, or
Windows 2000, and the NIC is not Plug and Play, you can use the Add
New Hardware Wizard in the Control Panel to install the drivers and set
up the card. (Remember to document all settings.)
If you are replacing (upgrading) an existing NIC, follow the same steps as just
described, with one addition. Before removing the card, document all its
settings. Figure 14.5 shows an example of an NIC information card. You can
use these cards to create a file documenting the specifics of the cards in your
network.
Figure 14.5 Information card
IMPORTANT
An improperly configured NIC could prohibit network access. Check
your settings carefully.
Network Cabling
Most networks need cables. The three main types are twisted-pair cable,
coaxial cable, and fiberoptic cable (FDDI [Fiber Distributed Data Interface]).
Twisted-Pair Cable
Twisted-pair cable, shown in Figure 14.6, consists of two insulated strands of
copper wire twisted around each other to form a pair. One or more twisted
pairs are used in a twisted-pair cable. The purpose of twisting the wires is to
eliminate electrical interference from other wires and outside sources such as
motors. Twisting the wires cancels any electrical noise from the adjacent pair.
The more twists per linear foot, the greater the effect.
Twisted-pair wiring comes in two types: STP (shielded twisted pair) and UTP.
STP has a foil or wire braid wrapped around the individual wires of the pairs;
UTP does not. The STP cable uses a woven-copper braided jacket, which is a
higher-quality, more protective jacket than UTP.
Figure 14.6 Twisted-pair cable
Of the two types, UTP is more common. UTP cables can be divided further into
five categories:
Category 1. Traditional telephone cable. Carries voice but not data.
Category 2. Certified UTP for data transmission of up to 4 megabits per
second (Mbps). It has four twisted pairs.
Category 3. Certified UTP for data transmission of up to 10 Mbps. It has
four twisted pairs.
Category 4. Certified UTP for data transmission of up to 16 Mbps. It has
four twisted pairs.
Category 5. Certified for data transmission of up to 100 Mbps. It has four
twisted pairs of copper wire.
Category 6. Offers transmission speeds up to 155 Mbps.
Twisted-pair cable has several advantages over other types of cable (coaxial
and fiberoptic): It is readily available, easy to install, and inexpensive. Among
its disadvantages are its sensitivity to electromagnetic interference (EMI), its
susceptibility to eavesdropping, its lack of support for communication at
distances of greater than 100 feet, and its requirement of a hub (multiple
network connection point) if it is to be used with more than two computers.
Coaxial Cable
Coaxial cable (see Figure 14.7) is made of two conductors that share the same
axis; the center is a copper wire that is insulated by a plastic coating and then
wrapped with an outer conductor (usually a wire braid). This outer conductor
around the insulation serves as electrical shielding for the signal being carried
by the inner conductor. A tough insulating plastic tube outside the outer
conductor provides physical and electrical protection. At one time, coaxial
cable was the most widely used network cabling. However, with improvements
and the lower cost of twisted-pair cables, it has lost its popularity.
Figure 14.7 Coaxial cable
Coaxial cable is found in two types: thin (ThinNet) and thick (ThickNet). Of the
two, ThinNet is the easiest to use. It is about .25 inches in diameter, making it
flexible and easy to work with (it is similar to the material commonly used for
cable TV). ThinNet can carry a signal about 605 feet (185 meters) before
signal strength begins to suffer. ThickNet, on the other hand, is about .38
inches in diameter. This makes it a better conductor, and it can carry a signal
about 1640 feet (500 meters) before signal strength begins to suffer. The
disadvantage of ThickNet over ThinNet is that it is more difficult to work with.
The ThickNet version is also known as standard Ethernet cable.
When compared to twisted-pair cable, coaxial cable is the better choice even
though it costs more. It is a standard technology that resists rough treatment
and EMI. Although more resistant, it is still susceptible to EMI and
eavesdropping. Use coaxial cable if you need
A medium that can transmit voice, video, and data
To transmit data longer distances than less expensive cabling allows
A familiar technology that offers reasonable data security
A Mixed-Cable System
Many networks use both twisted-pair and coaxial cable. Twisted-pair cable is
used on a per-floor basis to run wires to individual workstations. Coaxial cable
is used to wire multiple floors together. You should also consider coaxial cable
for a small network because you can purchase prefabricated cables (with end
connectors installed) in various lengths.
Fiberoptic Cable
Fiberoptic cable (see Figure 14.8) is made of light-conducting glass or plastic
fibers. It can carry data signals in the form of modulated pulses of light. The
plastic-core cables are easier to install but do not carry signals as far as glasscore cables. Multiple fiber cores can be bundled in the center of the protective
tubing.
Figure 14.8 Fiberoptic cable
When both material and installation costs are taken into account, fiberoptic
cable can prove to be no more expensive than twisted-pair or coaxial cable.
Fiber has some advantages over copper wire: It is immune to EMI and
detection outside the cable and provides a reliable and secure transmission
media. It also supports very high bandwidths (the amount of information the
cable can carry), so it can handle thousands of times more data than twistedpair or coaxial cable.
Cable lengths can run from .25 to 2.0 kilometers depending on the fiberoptic
cable and network. If you need to network multiple buildings, this should be
the cable of choice. Fiberoptic cable systems require the use of fibercompatible NICs.
Specifying the Right Cable
To ensure trouble-free operation, network cabling must match the system
requirements. Cable specifications are based on three factors: speed,
bandwidth, and length. Cables are designated with names like 10Base5. Speed
is the first number in the identification, representing the maximum
transmission speed (bandwidth) in Mbps. This will be 1, 5, 10, or 100. The
second part of the identification is bandwidth. It is either base or broad,
depending on whether the cable is baseband or broadband. The last part of the
identification refers to the cable length or cable type. If the unit is a number, it
is the maximum length of the cable segments in hundreds of meters (1 meter
is approximately 3.3 feet). In some cases, it can refer to 50-meter increments
(1Base5 is five 50-meter increments, or 250 meters). In other cases, it
represents cable type: T (twisted-pair) or F (fiberoptic). The following table
shows the common types of cables and their specifications.
Name
Description
Type
Segment
Speed
10BaseT
Common; being phased out for
UTP
100BaseT
.5 to 100
meters
10
Mbps
10Base2
Ethernet ThinNet
Coaxial
185 meters
10
Mbps
10Base5
Thick Ethernet
Coaxial
500 meters
10
Mbps
100BaseT Common
Twisted- .5 to 100
pair
meters
100
Mbps
The preceding table covers the basic cable requirements for the A+ networking
objective; however, there are many other forms of network connections. For
example, you'll find microwave links; forms of radio; and, for small offices and
homes, power-line networks (whose NICs have connectors that plug into wall
sockets, allowing regular wiring to carry the signal), and telephone-line
networks that use standard phone jacks to plug into existing lines. These have
relatively short ranges (generally limited to one office or one floor of a
building).
LAN Communication
A LAN is similar to a telephone system with one party line—not everyone can
talk at the same time. The difference is that, with a LAN, the speed is so fast
that it fosters the perception that many transactions are taking place at the
same time. Just like a one-lane road, the heavier the traffic, the slower it
moves.
Ethernet
Ethernet uses a system known as CSMA/CD (Carrier Sense Multiple Access
with Collision Detection). It also uses the bus topology discussed earlier in this
lesson. The term carrier sense means that the network card listens to the
cable for a quiet period during which it can send messages. Multiple access
refers to the fact that more than one computer can be connected to the same
cable. Collision detection is the ability to detect whether messages have
collided in transit (in which case neither message will arrive at its destination
and both will be retransmitted).
Fast Ethernet was developed to meet the increasing demands on networks.
Fast Ethernet works on the same principles as the original Ethernet but
operates at 10 times the speed. Ethernet transmits at 10 Mbps, and Fast
Ethernet transmits at 100 Mbps.
Token Ring
As described earlier, a token ring network uses a token as the basis for
deciding who can communicate on the network. Token rings transmit at 4 or
16 Mbps.
Network Protocols
A network protocol is a set of rules that govern the way computers
communicate over a network. For computers using different software to
communicate, they must follow the same set of networking rules and
agreements, called protocols. A protocol is like a language; unless both
computers are speaking and listening in the same language, no communication
will take place.
Networking protocols are grouped according to their functions, such as sending
and receiving messages from the NIC, or talking to the computer hardware
and making it possible for applications to function in a network. Early
computer networks had manufacturer-unique inflexible hardware and strict
protocols. Today's protocols are designed to be open, which means they are
not vendor-, hardware-, or software-specific. Protocols are generically referred
to as protocol families or protocol suites because they tend to come in groups,
usually originating from specific vendors.
The following is a list of standard network protocols:
IPX/SPX (Internetwork Packet Exchange/Sequenced Packet
Exchange). The NetWare core protocol developed by Novell in the early
1980s.
NetBIOS/NetBEUI (Networked Basic Input/Output
System/NetBIOS Enhanced User Interface). A local area protocol
developed by IBM and refined by Microsoft; originally the native protocol
for LAN Manager and Windows NT. IBM developed NetBIOS as a way to
permit small groups of computers to share files and printers efficiently.
NetBIOS is the original edition; NetBEUI is an enhanced version for more
powerful networks based on 32-bit operating systems.
TCP/IP (Transmission Control Protocol/Internet Protocol). A set of
standard protocols and services. It was developed by the Department of
Defense beginning in the early 1970s as part of an effort to link
government computers. This project led to the development of the
Internet. Because TCP/IP is the foundation of the Internet, as well as the
most widely used networking protocol, it is a good choice for networks.
AppleTalk. A networking protocol utilized by Macintosh computers.
DLC (Data Link Control) protocol. The oldest protocol of this group.
IBM developed DLC to connect token-ring-based workstations to IBM
mainframe computers. Printer manufacturers have adopted the protocol
to connect remote printers to network print servers.
Depending on the operating systems and the function of the network you work
on, you will probably use more than one network protocol. It's important to get
and install LAN drivers that can switch between protocols as needed. The
aforementioned protocol information provides you with a rudimentary
understanding of basic network techniques and terminology. However,
networks are a very complicated subject, and you should obtain additional
training resources before installing a network on your own.
Extending a LAN
The previous section on network cables mentioned some limits to the length of
cables. The requirements of today's LANs will often exceed the capability of
these cables. The following table lists several devices that can be used to
extend a LAN network beyond its normal limits.
Devices
Description
The main purpose of a repeater is to extend the length of a
network beyond its normal cable lengths. A repeater works
like an amplifier to increase or boost the signal to allow
transmissions over longer distances. Repeaters are used to
Repeaters
connect network segments (groups of computers on the same
network). They can also be used to connect segments
composed of different media (for instance, a ThinNet segment
to a fiberoptic segment).
Bridges
Bridges work like repeaters, but offer additional advantages.
They can isolate network traffic or problems. Should any
problems occur within one segment, the bridge will isolate
that segment and not affect other segments on the network,
thereby reducing the load on the network as a whole. Bridges
can also link segments that are not alike (such as Ethernet
and token ring).
Routers
Routers provide interconnectivity between like and unlike
devices on the LAN and WAN. Routers work like bridges, but
can connect networks using different protocols. They are able
to select the best route from one network to another network
based on traffic load. Routers determine the flow of data
based on such factors as lowest cost, minimum delay,
minimum distance, and least congestion. Routers are
generally used to create a WAN and connect dissimilar
networks.
Gateways provide all the connectivity of, and even greater
functionality than, routers and bridges. A gateway usually
resides on a dedicated computer that acts as a translator
Gateways between two completely dissimilar systems or applications.
Because gateways are both translators and routers, they tend
to be slower than bridges or routers. Gateways also provide
access to special services such as e-mail or fax functions.
Maintaining and Troubleshooting Networks
Maintaining and troubleshooting networks differ according to the operating
system. Therefore, you will need to refer to the operating systems' manuals
for detailed troubleshooting procedures. A thorough understanding of network
troubleshooting is not a requirement of the A+ Certification program. (The
section that follows describes some advanced certification programs that focus
on networks.) As an A+ technician, you should be familiar with some generic
troubleshooting concepts as presented in the following table.
Situation
Probable Cause
Reduced
bandwidth
Called a bottleneck, this occurs when the network doesn't
handle as much data as usual. A bottleneck is some
constraint that limits the rate at which a task can be
completed. If a task uses the processor, network, and disk
resources, and spends more of its time transferring data to
and from the disk, you could have a memory bottleneck. A
memory bottleneck might require additional RAM.
Loss of data
If data transfers are incomplete or inaccurate, check to
ensure that all network cabling and connectors are intact.
Fragmentation (see Lesson 2 of Chapter 9, "Basic Disk
Slow loading Drives") occurs when the operating system saves, deletes,
of programs and moves information. You must defragment the drive. If
and files
slow loading persists even after defragmenting, check for
memory bottlenecks.
You must manage software distribution to ensure that
users are not loading unlicensed software and computer
viruses on the network. One way is to load only software
Unauthorized
from a centralized location or server and then remotely
software
copy it to local hard disk drives. Depending on the NOS,
you can use built-in tools or third-party software to made
this task easier than manual tracking.
Traffic
overloads
A hardware or software failure can bring a LAN to a halt,
or the failure can result in more data traffic than the
network is designed to handle. You might receive an error
message or you might not see any signs other than poor
network performance. You must have a system in place
that can monitor and manage network traffic. To resolve
this problem, you will need to reduce the traffic on the
LAN or expand its capabilities.
Common
mode
failures
Some LAN component failures affect other components.
This is known as mode a common failure. For example, the
on-board logic of an NIC might jumble the data format.
The NIC will hand the result to the NOS, which might not
detect the error. If the NOS puts that data into a file, the
file will become corrupt.
Network
security
violations
Entire books address the subject of network security alone.
Every operating system is different, and every customer
requires a different level of security. First determine the
customer's needs, and then find and read the appropriate
documentation.
Network Certification
This chapter is designed to give you a foundation in networks and a general
understanding of network design and applications. Technician certification is a
growing trend in the computer industry. The A+ Certification exam touches on
network terminology and design; however, some of the most popular
networking certification programs are available through Microsoft and other
NOS manufacturers. These companies offer many levels of certification; you
should consult manufacturer Web sites and community colleges for detailed
course contents. Let's take a look at some of the available programs.
Microsoft Certified Product Specialist
Microsoft Certified Product Specialist (MCPS) certification is designed for
advanced end users, computer service technicians, and network administrators
who want to demonstrate expertise with a particular Microsoft product, such as
Windows NT Server or Windows NT Workstation. It is also a first step toward
becoming a Microsoft Certified Systems Engineer (MCSE).
Microsoft Certified Systems Engineer
The MCSE certification is one of the most sought-after certifications in the
computer industry. Qualified MCSEs plan, implement, maintain, and support
information systems in a wide range of computing environments using the
Microsoft Windows NT Server and the Microsoft BackOffice integrated family of
server products. To become an MCSE, you must pass four core modules and
two elective exams. For a detailed outline of the MCSE certification track,
please visit http://www.microsoft.com/trainingandservices.
Certified Novell Administrator
The Certified Novell Administrator (CNA) certification is frequently the first
credential earned by NetWare career professionals. CNA training provides you
with the critical day-to-day maintenance and management skills you need to
survive in the world of Novell NetWare and IntranetWare. The CNA
certification is the first step to becoming a Certified Novell Engineer (CNE).
Certified Novell Engineer
The CNE certification is currently one of the most popular credentials in the
field of networking. It can give a tremendous boost to the career of any
serious networking professional. Novell's certification curriculum is 50 percent
industry-generic—as a CNE, you are qualified to support Novell-specific
products as well as non-Novell products.
Lesson Summary
The following points summarize the main elements of this lesson:
The three benefits provided by a network are connections,
communications, and services.
The three primary network topologies are bus, ring, and star.
NICs provide the connection between the computer and the network
cabling.
The three network cabling types are twisted-pair, coaxial, and fiberoptic.
Network cabling is designated by transmission speed, length, or type.
Network protocols provide the rules for network communications.
Networks can be extended with repeaters, bridges, routers, and gateways.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Networks
The benefits provided by a network are connections, communications, and
services.
There are two types of networks: server networks and peer-to-peer
networks.
A network topology describes the physical layout of the network. There
are three basic topologies: bus, star, and ring.
To function on a network, each computer must have an NIC and an NOS.
The three types of network cabling are twisted-pair, coaxial, and
fiberoptic.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Name the three basic elements required to create a network.
2. The primary benefit of a LAN is its ability to share resources. Name some
of the other benefits of networking.
3. What is the difference between a peer-to-peer and a server-based
network?
4. Name the three network topologies.
5. What type of cabling do thin Ethernet and UTP cabling use?
6. What is the function of a network interface card?
7. Name the three main types of network cabling. What are their
advantages?
8. What is the purpose of network protocols?
9. Describe the functions of a router, a bridge, and a gateway.
10. What is the most widely used network protocol?
11. What is the difference between a LAN and a WAN?
12. Your network is showing signs of reduced bandwidth. What is causing this
problem?
13. Besides A+ Certification, what are some of the other computer-related
certifications available?
Answers
3 4
Chapter 15
Telecommunications: Modems and the Internet
About This Chapter
The rapid advance of the Internet into modern life has made
telecommunications activity a key function of the personal computer both at
work and home. The laptop user relies on the modem to link the mobile
machine to e-mail and the online world. This chapter covers the use of
modems, the fundamentals of the Internet, and configuration of a PC for
accessing the World Wide Web.
Before You Begin
This chapter assumes basic familiarity with the Microsoft Windows user
interface and PC serial ports. Some experience using the Internet and
telecommunications is helpful, but not necessary.
3 4
Lesson 1: Modems
Once an expensive and complicated option, the modem is now an integral part
of the modern PC, thanks to the popularity of the Internet, faxes, and e-mail.
After this lesson, you will be able to
Define how modems transmit data
Define the difference between serial and parallel data transfer
Install a modem
Troubleshoot basic modem and communication problems
Set up and test a modem
Estimated lesson time: 45 minutes
Modem Basics
A modem is a peripheral device that enables computers to communicate with
each other over conventional telephone lines or cable lines, or even without
wires. The word modem comes from combining the words modulator and
demodulator. In radio parlance, to modulate a signal is to change the
frequency (FM) or amplitude (AM) of a carrier (fixed signal) by superimposing
a code (voice or other information) on top of the signal. The reverse is to
demodulate, to remove the fixed signal and have the superimposed code
remain. For many years, this has been an effective way to communicate over
long distances, using both wires and radio waves.
ISDN (Integrated Services Digital Network) devices offer a high-speed digital
alternative to modems. Terminal adapters (TAs) link the computer digitally to
the telephone line without the need for either complicated handshaking or
modulation conversion. This makes ISDN connections even faster (under
proper line conditions) than the simple bit transfer rating might imply. Most
ISDN products can also use two 64 K bits per second (bps) lines at once,
allowing transfers of up to 128 bps.
The following table defines some basic terms used with modem
communication.
Term
Definition
Baud rate
The number of events, or signal changes, that occur
in one second. It was used as an early
measurement of how fast a modem could send data,
because, at that time, modems transmitted data at
a speed equal to the baud rate (1 bit per cycle).
Today's high-speed modems use complex signals to
send more data; therefore, data transfer can exceed
baud rate. The baud rate is limited by the capability
of copper wires to transmit signals.
bps
Stands for bits per second—the speed at which a
modem transmits data. Typical rates are 14,400,
28,800, 33,600, and 56,600 bps. These numbers
represent the actual number of data bits that can be
transmitted per second.
Browser
Software used to explore sites on the World Wide
Web using HTTP (Hypertext Transfer Protocol).
Bulletin board
system (BBS)
Interactive software that offers the user the ability
to log on directly to a remote computer to post and
retrieve messages and to upload and download files.
Some BBSs offer the opportunity to chat live with
other members who are online at the same time.
The Internet has changed the very nature of BBS
software, replacing it with discussion boards.
Download
The act of transferring a file from a remote
computer (host) to a local computer (client). When
downloading, you are receiving a file.
DTMF
Stands for Dual Tone Multiple Frequency, the
technology behind the tones of a touch tone phone.
Internet
A worldwide, online network that links computers
by means of the TCP/ IP (Transmission Control
Protocol/Internet Protocol) protocol. (See TCP/ IP,
later in this table.)
Internet server
A computer and software combination that provides
a gateway and supporting services for linking other
computers to the Internet.
IP
Internet Protocol; the network protocols used to
define how data is transmitted on the Internet.
IP address
Internet Protocol address; a unique, 32-bit address
that identifies every network and host on the
Internet. (A host is the TCP/IP network interface
within the computer, not the computer itself; a
computer with more than one network interface
card [NIC] can have more than one IP address, one
for each card.)
ISDN
A digital telephone connection like a modem that
uses digital links and offers speeds about five times
that of an analog modem. The ISDN system is a
packet system that can also handle voice
communication.
ISP
Internet service provider; a company or server that
provides the connection gateway to the Internet.
Logging on
The process of sending the appropriate signals and
gaining access to a remote computer over a modem
or other remote connection.
Modem
A device for converting a computer's digital data
stream to and from an analog form so that it can be
sent over a telephone line.
Offline
Status of a computer that is not connected to
another device over a modem or other
telecommunications device.
Offline reader
A program designed to display e-mail messages or
other information that has been downloaded to one
computer from another.
Online
An active connection between two computers,
making possible the exchange of data.
POTS
Plain Old Telephone Service; a common term that
denotes the basic analog phone network as
compared to newer digital networks used for packet
transfer of data.
Protocol
A set of rules that govern the transfer and
verification of data between two or more systems.
Proxy server
A computer/modem/software combination that
manages Internet traffic to and from a LAN (local
area network). A proxy server can provide other
features, such as document caching and access
control.
Settings (modem)
Configuration required by the telecommunications
software for data to be transmitted. Usually 8 bits,
no parity, 1 stop bit (8-N-1) will work. Some BBSs
require special terminal emulation, a software
configuration that mimics the operation of
proprietary mainframe terminals like the VT100.
TCP/IP
Transmission Control Protocol/Internet Protocol; the
name given to a collection of protocols that were
designed for use on the large-scale, mixed-platform
environment that became the Internet.
Telecommunications
The ability to transmit data over telephone lines to
a remote computer. Often abbreviated as telecom.
An application that allows two computers to
Telecommunications communicate with each other. Both computers must
software
use compatible software for communication to take
place.
Upload
The ability to transfer a file from a local computer
to a remote computer. When uploading, you are
sending a file to another computer.
Webmaster
A person who manages a Web site on the Internet's
World Wide Web. The Webmaster's duties are
analogous to those of a BBS sysop.
Communication
Two basic problems arise from using modems to transmit data. The first
problem is that, as we saw in Chapter 4, "The Central Processing Unit,"
computers transfer data using 8, 16, or 32 parallel wires or buses, whereas
telephone systems use only two wires (see Figure 15.1). The second problem
is that telephone and radio systems use analog signals (based on waveforms),
and computers use digital signals, either on or off, as shown in Figure 15.2.
Figure 15.1 Serial and parallel communication
Figure 15.2 Analog and digital signals
A modem resolves both of these problems by acting as an analog-to-digital (AD) converter as well as a modulator/demodulator.
Serial/Parallel Conversion
Virtually all personal computers use a family of chips produced by National
Semiconductor to run serial ports. Known as UARTs (universal asynchronous
receiver-transmitters), these chips convert an 8-bit-wide parallel data path to
a 1-bit-wide serial path.
The UART has gone through several major changes during the PC era, and
there are many different types of UARTs with different functions. The following
table lists several of the more common ones.
Chip
Description
The original chip used in the IBM PC, the INS8250 operated at
speeds up to 56 kilobits per second (Kbps). The 8250A and
INS8250
8250B incorporated fixes for minor bugs in the original design,
but the 8250 series was unreliable at speeds over 9600 bps.
16450
Designed for 286-based PCs, the 16450 was the first UART that
reliably operated at 9600 bps and higher.
16550
The 16550 allowed use of more than one direct memory access
(DMA) channel to achieve improved throughput over the
16450.
16550A
An improved version of the 16550, the 16550A is the only
UART installed on today's computers. It adds support for first
in, first out (FIFO) communication. This is the only UART that
should be installed in current PCs or add-on cards that are used
to provide expansion-card-based COM ports.
Today, virtually all systems are equipped with UART devices fast enough for
the current range of modems and other telecommunications devices. That is
not true of all older systems. The newer versions of Windows are all very
adept at configuring modems for use with the Internet. DSL, ISDN, and cable
connections may require custom setup and configuration.
You can easily determine settings and, often, which UART chip is installed in a
computer by using the System Information utilities or Control Panel functions
that come with the various versions of Windows or the MSDs (Microsoft
Diagnostics) that are a part of DOS. Open the Communications Port (COM1)
Properties dialog box to review settings (see Figure 15.3).
Figure 15.3 Communications Port (COM1) Properties dialog box
Digital Communication
The movement of data from one computer to another over telephone lines is a
multistep process. The first step is conversion of the data from parallel to
serial form. The digital information must then be broken into uniquely marked
packets (this allows the receiving computer to distinguish one byte from
another).
Asynchronous Communication
Asynchronous communication is any data transmission that does not link the
two devices with a common data clock. This is useful because the length of
time between sending a packet and its receipt on the other end can vary
between the communicating devices. A signal called a start bit is sent at the
beginning of each segment, and a signal called a stop bit is sent at the end.
These let the receiving device note the boundaries (beginning and end) of a
transmission packet. Early PC modems were almost always asynchronous
devices operating at speeds of no more than 18,000 bps.
Synchronous Communication
Synchronous communication sends data blocks at strictly timed intervals that
are monitored at both ends. Modems operating at speeds up to 56 Kbps over
standard telephone audio lines are usually synchronous devices.
Communications Protocols are standard "languages" used to transmit data
between systems. They involve a wide range of methods for ensuring that the
data sent at one end is accepted at the other. The following is a summary of
how these protocols work.
1. Before a modem sends any data, a communication link must be
established. To do this, the modem sends a series of standardized bytes—
called sync bytes—to the device it is to communicate with.
2. The modem on the other end receives the sync bytes.
3. The receiving modem perceives that it is receiving sync byte data and
synchronizes with the incoming data.
4. After sending the sync bytes, the sending modem adds a start-of-text
(STX) character.
5. The data bytes are sent. The data in synchronous transmission is
processed in packets or in blocks of fixed length, depending on the
protocol used.
6. Each packet ends with an end-of-text (ETX) character and two errorchecking characters called CRC (cyclical redundancy check) characters or
BCCs (block check characters).
7. The receiver then responds with an ACK (acknowledgment character) if
the data is good, or an NAK (negative acknowledgment) if transmission
errors have occurred.
NOTE
In asynchronous communication, the receiving modem does not
respond—it just reads the data and acts on it—unless a timing
error is reported. In synchronous modes the receiving modem
must respond.
Parity
Asynchronous communication packets have an optional parity bit that is used
for error detection. The receiving port uses the parity bit to verify whether the
data is intact or has been corrupted. There are two types of parity:
Even parity. The sending computer counts the 1s in the data part of the
packet; if the number of 1s is even, the parity bit is 0—this makes the
total number of bits even. If the number of 1s in the data part of the
packet is odd, the parity bit is set to 1—again making the total number of
bits even. The receiving port counts the data bits and compares its
answer to the parity bit. If the two fail to match, an error is reported, and
a request to retransmit the packet is passed to the sending computer.
Odd parity. This works in exactly the same way as even parity, except
that the total number of bits must be odd.
The use of parity bits is optional. The quality of data transmission and
telephone lines has improved to the extent that parity bits are no longer
required. However, if data accuracy is critical or telephone-line quality is
questionable, use parity.
Hardware
Now that we've seen how modems send and receive data, we'll examine the
hardware involved.
Internal Modems
The entire modem and even its serial port can be accommodated on a single
expansion card. This configuration offers lower cost than that of an external
modem, but it is more prone to compatibility problems with either the onboard UART or the COM port IRQs (interrupt requests).
USB Modems
Most new PCs offer two universal serial bus (USB) ports, either of which can be
used to attach a modem. USB is a hot swap (the device can be added or
removed without powering down the PC), Plug and Play interface (see Chapter
8, "Expansion Buses, Cables, and Connectors") well suited to this task. To
install a modem this way, usually all that is required is to attach a USB cable
between the modem and PC, connect the phone-line cable between the modem
and a wall jack, and load the modem-driver software from the manufacturer's
configuration disk when prompted.
External Analog Modems
The original modems used a pair of cups to cradle a telephone handset over a
built-in speaker and microphone; in this way, the modem would send and
receive tones acoustically, and the telephone handset would relay the tones.
Today, the external modem is usually a rectangular box with a row of status
lights on the front, a speaker to give audible feedback, and a number of ports
on the back. Two of those ports are telephone jacks—one to connect to the
wall line and the other to pass the telephone signal to a phone for regular
voice conversations when the modem is not in data mode. A third port on the
back of the modem is a serial port using a standard 25-pin RS-232 connector
that passes data to and from a serial port on the PC.
ISDN Terminal Adapters
Until about 30 years ago, the North American telephone network was an
analog system connecting phones by means of a grid of copper wires. Today,
the long line sections (intercity telecom lines) are part of a packet-based,
digital switching system, but the final run from the local switch to most homes
is the aged copper-wire POTS line.
ISDN is an all-digital phone connection that uses special high-quality phone
lines to ensure clean, high-speed data transfers directly to the user's home or
business. B channels (bearer channels) carry both voice and data with a
maximum speed per channel of 64 Kbps. A companion D channel (data
channel) handles signaling at 16 Kbps (or 64 Kbps, depending on service
provided by the carrier).
NOTE
In the context of ISDN communications, K means 1000; in other
computing contexts, K means 1024.
ISDN connections do not make use of a modem. Instead, a terminal adapter
(TA) serves as the interface for both computers and analog phones served in a
location. Most small business and residential customers make use of a TA that
has a 25-pin serial connection to attach to a computer serial port. It also
provides analog telephone connections for two lines.
ISDN is more complicated to install than a modem and should be set up using
the help of a vendor or the local telephone company. After installation, ISDN
functions like a high-speed modem, offering not only faster data transfers, but
faster connections to remote ISDN providers such as ISPs. Because each TA
unit is completely digital, there is no testing of the nature of the remote
source by the hardware to establish the maximum connection rate (as with a
modem), and links are typically established in less than 3 seconds.
The RS-232 Port
External modems and TAs communicate with their host computers by means of
an RS-232 communications port. The EIA (Electronic Industries Association)
developed the RS-232 standard for low-speed data communication; the
standard defines a series of signals that are sent between two
telecommunications devices to indicate line and transmission status. The
following table shows the most common signals.
Signal
Definition
CTS
Clear To Send
DCD
Data Carrier Detected
DSR
Data Set Ready
DTR
Data Terminal Ready
RI
Ring Indicator
RTS
Request To Send
RTSRD
Request To Send/Receive Data
RS-232 Cables
RS-232 connections can make use of either 25-pin or 9-pin connectors. On
many PCs, the end attaching to a modem or TA has a 25-pin connector,
whereas the PC has a 9-pin connector. The following table presents the layout
and signals for both.
Description
Protective
Ground
Transmitted
Pin Outs
on 9-Pin
Cable
—
Signal
25-Pin
Cable
—
Direction
—
DTE (Data Terminal
Data
3
TD
Equipment)→DCE (Data
Communications Equipment)
Received
Data
2
RD
DCE→DTE
Request To
Send
7
RTS
DTE→DCE
Clear To
Send
8
CTS
DCE→DTE
Data Set
Ready
6
DSR
DCE→DTE
Signal
Ground
(Common)
5
—
—
Data Carrier
1
Detected
DCD
DCE→DTE
Data
Terminal
Ready
4
DTR
DTE→DCE
Ring
Indicator
9
RI
DCE→DTE
Data Signal
Rate
Detector
—
DSRD
DCE↔DTE
Telephone-Line Basics for Modems
Modem connections to the telephone service are made using two wires (ring
and tip) that are used in a standard telephone jack. The wires are named for
the plug wires used in the original telephone lines by which telephone
operators would manually connect two telephones at the phone company
switchboard. There are two versions of the telephone jack:
Half-duplex. The RJ-11 has only two wires, which make up one line.
Therefore, only one signal can be sent or received at a time.
Full-duplex. The RJ-12 uses four wires to make up two lines; it can be
used to simultaneously send and receive.
Multifunction Modems
Most modems offer some form of fax capability, along with software that adds
functions beyond the average, small, stand-alone fax machine. Such a modem
is usually labeled a fax modem. They can store faxes, both incoming and
outgoing, for reference or online reading. Most allow direct faxing of a
document from a word processor, generally by using the print command to
send the pages to the modem, where they are converted on the fly to the
bitmap form used to send and receive fax transmissions. Many programs let
you automatically attach a predesigned cover sheet with each fax.
Another addition to the basic data out/data in modem is voice mail. Here, the
PC and telephone work just like an answering machine. If the phone rings and
the modem does not detect either a data or fax tone, it switches modes and
streams a recorded message (the outgoing message). The caller can be
prompted to record a message for the owner, and in some cases the modem
will even forward a pager call or fax with the message contents.
Modem Installation
With the advent of Plug and Play technology; Windows 98, Windows Me, and
Windows 2000; and the growing popularity of the USB port, installing a
modem has become a generally simple process. Summaries of the general
installation process for both internal and external modems follow.
NOTE
A good technician always reviews the product documentation
before setting up a modem to ensure proper operation and the
inclusion of all desired features.
Internal Modem Expansion Card
As with installing any card or internal board, remember to take the proper
precautions against electrostatic discharge (ESD), and, of course, back up your
data before you open the computer case. Follow these steps:
1. Check and document the current IRQ settings and I/O (input/output)
addresses in the computer. Make a note of available IRQs and addresses.
2. Configure IRQ and I/O settings for non–Plug and Play–compliant systems:
Set the modem to an unused COM port and IRQ.
3. Install the board. Physically install the board in an available expansion
bus slot.
4. Install any software. Follow the software setup routine and, if needed, fill
in the modem settings and any dial-up connections the user requests for
Internet access or for logging on to a remote system. To avoid generating
any security concerns, do not ask for or accept account passwords. Show
the user how to set that part of the connection personally.
For older machines running Windows 3.x or MS-DOS and non-Internet
connections under Windows 95 and later versions, additional work might
be required. Here is a sample of how this part of a typical Windows 3.x
SYSTEM.INI file might look:
[386enh]
COM3Irq=5
COM3Base=03E8
5. Set up the command set. Any software that will access the modem must
know the correct command set to use for that modem. This means
identifying the type of modem so the software will use the correct AT
commands. When all else fails, try using a Hayes-compatible modem
setting.
6. Document your work. Write down all the new settings and changes.
External Modem
External modems are easier to install than internal modems because they do
not run the risk of conflicting COM ports.
1. Connect to a COM port. Choose either COM1 or COM2. Be sure to confirm
that the COM port you are using is assigned to the connector on the
computer. If the computer is using a serial mouse, that will be using one
of the COM ports, too, and this sets up a potential conflict. You can also
use COM3 or COM4 if they are properly installed and configured.
2. Plug in the cabling. Connect the modem to its power source and to the
computer. You will also have to connect a telephone line (RJ-11) from the
wall jack to the modem.
3. Configure the software to select the required COM port and the type of
modem (command set) used by the specific modem installed if the
operating system or installer does not identify the settings properly.
Modem Speeds
When installing and using a modem, the primary factor you should consider is
speed. The multimedia World Wide Web requires far more speed than the
simple data transfers of just a few years ago. Modem speed is measured in
baud and bps.
Baud Rate
As mentioned earlier, baud rate refers to how fast a modem can transmit data.
Technically, the baud is the number of voltage or frequency changes that can
be made in one second. When a modem is working at 2400 baud, this means
that the basic carrier frequency has 2400 cycles per second. Due to
restrictions imposed by the physics of the wiring, a dial-up phone line can go
up to 2400 cycles, a baud rate of 2400.
If each cycle is one bit, the fastest rate at which data can be transmitted is
2400 bps. However, by using different types of modulation, more than one bit
can be transmitted per cycle. Earlier modems used the baud rate to measure
their speed (see Figure 15.4).
Figure 15.4 Baud
Bits per Second
The actual modem speed, or rate, at which data is transmitted is measured in
bps. If a modem modulates one bit for each baud cycle, then the modem speed
is 2400 bps. If a 2400-baud modem modulates two bits for one cycle of time,
the modem is said to have a speed of 4800 bps (not a baud rate of 4800). If
four bits are modulated with one cycle of time, then a modem speed of 9600
bps is achieved.
NOTE
Do not confuse baud with bps.
Modem speed standards are designated by the CCITT (Comité Consultatif
International Télégraphique et Téléphonique), an international body that
develops fax and modem standards. The CCITT is now a branch of the
International Telecommunication Union—Telecommunication Standardization
Sector (ITU-T). The following table lists the standard rates designated by the
CCITT.
CCITT Term
Bps
V.21
300
V.22
1200
V.22bis
2400
V.23
1200 bps in one direction and 75 bps in the other
V.29
9600
V.32
4800 and 9600
V.32bis
14,400
V.32fast
28,800
V.34
28,800
V.42bis
38,400
V.90
56,600
NOTE
The term bis refers to the second revision of the standard.
Fax Speeds
Faxes are transmitted using one of several variations of an international
standard. These standards are divided into four groups.
Groups 1 and 2
Groups 1 and 2 are based on 300-baud communication rates. They pertain to
analog devices and do not include a modem. Group 1 transmits one page in 6
minutes. Group 2 transmits one page in 3 minutes.
Group 3
Group 3 is for digital equipment and can use the same modem for data and
fax. Not all modems in this group are compatible. Group 3 is comprised of
several subclasses, as shown in the following table.
CCITT Term
Bps
V.21 Channel 2
300
V.27 Turbo
4800
V.29
9600
V.17
14,400
Group 4
Group 4 allows the highest resolution of output to date (400 by 400, up to
1200 dots per inch [dpi]). These speeds are for use with digital telephone
circuits, ISDN, or leased lines.
Information Transfer Protocols
Communication relies on protocols. To ensure clear and clean communication
without any errors, the device on each end must follow a very strict set of
rules. If either device violates any of the rules, the communication will fail.
This set of rules is called the FTP (File Transfer Protocol).
All the necessary protocols should be included with the software that came
with the modem. After communication is established with the host (usually the
computer that receives the call), it can be asked what type of protocol to use.
The call initiator can then select the matching protocol before starting a file
transfer. Both computers must use the same protocol. There are five basic
protocols used by modems.
ASCII
This protocol uses the standard ASCII (American Standard Code for
Information Interchange) character set, just like typing directly from a
keyboard. ASCII protocol has no error-checking or compression features. It is
simple, uncomplicated, and is used with simple character-based data. It is not
a good protocol for transferring program files.
Xmodem
Xmodem is the next level of protocol. Xmodem includes error detection, which
makes it more suitable for transferring program files. It transfers 128-byte
blocks of data and one checksum (error-checking) character. The receiving
computer calculates a new checksum and compares it to the one transmitted.
If they are the same, the receiving computer transmits an ACK. If they are
different, it sends back an NAK, and the transmitting computer then
retransmits the data block. The protocol uses parity error checking, which is
not perfect. If two errors were to occur—that is, if the first error were to
change the parity bit, and the second error were to change it back to its
original state—the second would cancel the first, and no error would be
reported. The result can be a corrupted file or random characters on the
display.
Ymodem
Ymodem is faster than Xmodem. Ymodem transfers data in 1024-byte blocks;
therefore, less time is required to verify data with ACKs and NAKs.
Zmodem
Zmodem shares all the features found in Xmodem and Ymodem protocols. It
also adds a few new features, including crash recovery, automatic
downloading, and a streaming file transfer method. This is the protocol of
choice for most situations.
Kermit
The Kermit protocol is rarely used today. It was the first of the synchronous
protocols for uploading and downloading data to and from a mainframe
computer.
Handshaking
Did you ever wonder what all the noise that occurs when analog modems or
fax machines begin to communicate means? The devices are handshaking, or
negotiating, the rules (protocols) of communication. Because all modems and
computers are not exactly the same, there must be some way for the two
machines to determine how to communicate. That is what happens in that
short burst of information between the two modems: Decisions are made about
what transmission speed to use (the fastest speed of the slowest device), how
the data will be packaged, and which device will control the transfer. If both
machines cannot satisfy any of the parameters, the negotiations will fail and
both parties will disconnect.
TIP
If you experience communication difficulty between two modems,
be sure that you have not limited one of them to parameters that
the other is unable to meet. For example, if one modem has a
minimum speed restriction imposed by the software, it might need
to be changed before it can communicate with other modems.
Connections between a sending device (sometimes referred to as DCE) and a
receiving device (DTE) are called handshaking signals. They ensure that each
sending and receiving device is in sync with the other. The flow control of data
between modems is handled by the modems themselves. However, the local
flow control between modem and COM port can be set by the user. There are
two types of flow control:
Hardware flow control. This takes advantage of some of the extra wires
in the serial connection between the modem and the COM port. These
wires are used to let the other device know that the DCE is ready to send
or receive data. The wires are named RTS and CTS. Hardware
handshaking is sometimes referred to as RTS/CTS.
Software flow control. This uses special characters known as XON and
XOFF to let the other device know that the DCE is starting to send data or
that the data transmission is finished. Software handshaking is slower
and not as dependable as hardware handshaking. Only some very old
modems use software handshaking. If given a choice, always use
hardware flow control.
Modem Standards
As with every other communication device, standards are needed to ensure
that both sides speak the same "language." Modems have their own set of
standardized communication conventions.
Error Detection
Some modems offer various forms of hardware error detection and correction.
Such features usually require matching firmware in the modems at both ends.
Data Compression
Data compression is a means of shrinking files into smaller packets, resulting
in faster connections and lower space requirements on the host and client
machine for storage. Some modems can perform on-the-fly data compression;
both modems must be able to understand the compression for it to work. Onthe-fly compression significantly enhances the amount of data sent between
modems during a given time period. There are now a variety of industry
standards for data compression, based in part on the work done by various
Internet-related committees.
Communication Standards
There were no standards during the early days of modem communication. The
only way to ensure data transmission was to place identical modems at the
sending and receiving ends of the transmission. Compatibility was a great
concern, and proprietary modems were the norm.
Today, modems comply with several standards. There are two sources for
these standards:
Manufacturers have placed specifications of their modem functions in the
public domain. These specifications can now be copied and used by any
manufacturer. If enough manufacturers use a specification, it becomes a
standard on its own merits.
Standards committees are formed when there is enough interest
expressed by users, vendors, or regulatory committees to develop a set of
rules for a class of data or modems.
The following material details the standards that evolved with
telecommunications. Most of these are obsolete to the average user since the
advent of faster devices, alternatives to modems, and the Internet.
Early Bell Standards
Bell Telephone produced the first generally accepted modem standards (103
and 212A); they developed out of the market-dominant position of the
telephone company in telecommunications. To compete, other vendors offered
products that would recognize the Bell command set. This scenario occurred
more than once with subsequent standards.
CCITT Standards
The CCITT modem standards are commonly known as Vdot standards because
each is named using the letter V followed by a decimal point and a number.
The Vdot standards set out detailed requirements for the use of various
modem speeds, incorporation of data-compression schemes, and error
correction.
MNP Standards
The MNP (Microcom Networking Protocol—named for Microcom, the company
that developed them) set forth a series of error-correction methods.
Error-Detection and Data-Compression Protocols
In addition to speed standards, some CCITT standards include error-detection
and data-compression protocols. The following table shows the standards that
include error detection.
Standard Baud
Bps
Type
Comments
V.42
2400 2400 and up Error correction
MNP 1-4
2400 2400 and up Error correction
V.42bis
2400 9600/38.4K
Data compression V.42 must be present.
MNP 5
N/A
Both
N/A
56-Kbps Modems
Telephone lines are capable of carrying 56 Kbps of data; however, conversion
from analog to digital signals and back comes with a price: a speed limit of
33.6 Kbps. Because many telephone systems are now digital, it is possible to
transmit, in some instances, at a full 56 Kbps in one direction. The return
data, however, is still limited to 33.6 Kbps. For these reasons, it is unlikely
that you can achieve a full data transfer rate with a 56-Kbps modem. To
achieve the best performance, the following conditions must be met:
Digital-to-analog conversion should be limited so that it takes place only
once within the network. Each conversion slows the communication
process.
The host must be connected digitally.
Both modems must support the 56-Kbps technology.
Originally, there were three 56-Kbps modem standards: K56flex, x2, and V.90.
Unfortunately, these standards were not compatible at 56 Kbps, so to achieve
the highest possible speed, both modems needed to use the same standard.
Several companies developed the K56flex standard, and U.S. Robotics
developed the x2 standard. Currently, the V.90 standard has replaced both the
K56flex and the x2, and most 56-Kbps modems can be upgraded to this
standard. If you have a 56-Kbps modem and want to upgrade to V.90, check
the manufacturer's Web site for instructions and download the appropriate
software.
Modem Commands
Just like the early computers that needed MS-DOS commands to tell them
what to do, modems also need commands. Programmers also needed a
standard command set to incorporate the use of modems into their software.
Unfortunately, there are no true standard command sets for modems because
manufacturers are free to create their own. There is, however, one set of
commands that has been accepted as a de facto standard. Most modems today
are Hayes-compatible. In the early 1980s, Hayes developed the AT command
set.
These commands are very useful as diagnostic tools for today's computer
professional. To use these commands, make sure the communication software
is loaded and the computer is in terminal mode. Unless the modem is set up to
autoconnect (online mode), it will be in command mode and ready to accept AT
commands. The following table lists some of the more useful AT commands
used by computer professionals.
Command
Function
AT
Lets you know that your modem is plugged in and turned on.
The mode should respond with OK.
ATE1
Echoes the command on the screen.
ATE0
Turns off the echo to the screen. Some modems will not run
correctly when the echo is on.
ATH
Takes the telephone off the hook. Should elicit a reply of OK
or 0 from the modem, or a dial tone and an OH indicator if
it's an external modem.
ATM1
Turns the speaker on for the dial tone. ATL0 is the lowest
volume and ATL2 is medium volume.
ATM0
Turns the speaker off.
ATD
Takes the phone off the hook and dials a number if one is
included with the command (for example, ATDT555-2222).
The second T is for tone; substitute P for a pulse phone.
Include a W (ATDTW) to instruct it to wait for a dial tone
before dialing. Include a comma anywhere after the
command to instruct it to pause before continuing to dial.
ATQ0
Enables result codes. A troubleshooting aid. Type ATV1 prior
to this command and you will get back verbose result codes
(OK-BUSY-CONNECT 2400,9600-COMPRESSION:V.42bis).
ATQ1
Disables result codes.
ATH, ATH0 Hangs up the modem.
ATX
This resets your modem to a predefined state. You can
configure your own reset state. If it wasn't set previously, it
can be reset to the factory's default setting.
Troubleshooting
It can be very frustrating when a modem does not function as expected.
However, you can follow these simple guidelines to determine whether the
modem is really broken or something else is the culprit.
Possible Cause
Possible Solution
New hardware
was added to the
computer and
Check for IRQ and I/O conflicts.
now the modem
doesn't work.
New software
was added to the
computer and
now the modem
doesn't work.
Check for IRQ and I/O conflicts. Cards that were
configured for software can be inadvertently changed
by corrupted software or by the installation of new
software.
The software
says there is no
modem.
Make sure the software is checking the correct port.
Reconfigure or reinstall the software (there might be a
corrupt driver).
Modem works
sporadically.
Try another modem type.
Check the phone lines.
Modem does not
hang up the
phone line.
A power surge (often caused by a lightning strike) can
cause this problem. If manual disconnect and
reconnect allows the modem to disconnect, but it does
not automatically drop the connection in the future,
replace or repair the modem.
Lesson Summary
The following points summarize the main elements of this lesson:
Modems convert parallel digital data to and from serial analog data.
Modem speeds are based on bps.
CCITT (now ITU-T) establishes standards for modem communication.
AT commands are used to manually communicate with and test a modem.
Modems can be installed internally or externally.
The primary modem problem is IRQ conflicts.
Modems and ISDN TAs do similar things but are not the same kind of
device.
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Lesson 2: The Internet and Web Browsers
Once the domain of academics and defense contractors, the Internet is now a
part of everyday life. Browsing for news, chatting with online friends, and
exchanging e-mail are common PC activities for young and old.
After this lesson, you will be able to
Define how the Internet works
Define basic Internet-related terms
Install and configure a browser
Set up an Internet account
Estimated lesson time: 45 minutes
The Internet
The Internet, commonly known as "the Net," is the most extensive WAN (wide
area network) in the world—a network of networks working together. This
relatively new communication technology has begun to affect our lives as
significantly as television and the telephone. When most people talk about
using the Internet, they talk about which Web sites they have visited or people
they have met online.
Most LANs make use of passwords and other forms of security, but the Internet
is one of the most open networks in the world. Some common Internet uses
include communication; locating lost friends and family; researching
information for school or work; and locating businesses, products, or services
(such as travel). The Internet can be a valuable resource for virtually anything
and everything.
Although detailed knowledge of the inner workings of the Internet is not a
requirement of the A+ Certification Exam, you will find questions on the exam
on various aspects of its use. In addition, knowing how to find drivers and
technical information on vendor Web sites can save time and effort in
providing customers with updates and repairs.
Internet Basics
The Internet is really a collection of services. Let's take a look at the most
important services and the major concepts behind them.
The World Wide Web
When people say they are "surfing" the Net, they are probably visiting the
collection of hyperlinked Web sites known as the World Wide Web ("the Web"
or WWW). These Web sites are located around the world, and their numbers
continue to grow by the thousands every day. Each Web site within the Web
has a unique address called a URL (Uniform Resource Locator).
NOTE
The Web is not the Internet; it is only part of the Internet.
Although it is currently the largest, most popular, and fastestgrowing part of the Internet, it represents only a fraction of the
Internet services available that include FTP, Gopher, and Telnet.
Web Sites
The Web is a network of host sites that can be accessed for information. Most
pages provide information to clients using the Hypertext Transfer Protocol
(HTTP— this is the http:// seen in the full address line in a browser).
Pages can be hyperlinked so that, when a user clicks on a text string or image
that has been coded as a link, they are shown the contents of the linked page.
All Web pages use some derivative of SGML (Standard Generalized Markup
Language) to code pages so the browser can "read" the instructions on how to
display and link material on the pages. A committee of government and
industry experts in networking, information systems, and publishing designed
this standard.
A loose form of an SGML application, Hypertext Markup Language (HTML) was
designed to tag the content of Web pages. If you choose to view the source
code of a Web page in your browser, you can see the markup that tells what
each portion of the page is, if it has hyperlinks, and any special information on
how to display it.
Some purists lament how open the design of HTML is, but that openness allows
for additional plug-ins that let browsers handle animation, sound, streaming
video, and other enhancements to the Web experience.
Browsers
A browser is the most common Internet application for the end user. The two
most popular are Microsoft Internet Explorer and Netscape Navigator. These
programs "open" Web pages for viewing, can access and download remote files
using FTP, and perform other routine online tasks. Figure 15.5 shows a
browser in action viewing the Microsoft Web site.
Figure 15.5 Surfing the Web with Microsoft Internet Explorer
Electronic Mail
Electronic mail, usually known as e-mail, is the most commonly used function
of the Internet, allowing users to send and receive messages (and files)
electronically to and from millions of people all over the world. Electronic
mailing lists allow users to join group discussions with people who share their
interests. Like regular mail (now often called snail mail), e-mail is also sent to
an address (a virtual one).
To make use of e-mail, one must have access to an e-mail server, an account
on that server, and a program to send and receive messages. Microsoft
Windows includes Microsoft Outlook Express as an e-mail client. Several
others, like Eudora and Hotmail, are available online. You can also find several
products either as stand-alone software or bundled (as in Office 2000) as
commercial software products in stores. Virtually all ISPs offer e-mail as part
of their packages, and free accounts are available as well.
To set up an account, you will need to know the address information for both
the inbound and outbound mail servers (obtained from the provider), as well
as the account address (usually in the form of
mailto:[email protected]). The account will have a password that can
usually be stored so the user does not have to enter it each time mail is sent
or received. Check with the vendor and program documentation for detailed
information on setting up specific programs to handle e-mail and connecting to
an ISP. (Windows 95 and 98 and Windows Me all include an Internet
Connection Wizard that makes it easy to connect to the Internet by prompting
you for all of this information.)
NOTE
When setting up programs like Microsoft Outlook, be sure to ask
the client if and how often he or she wants mail checked. If the
client does not have a permanent connection to the Internet,
charges may be made based on the connect time. Checking
frequently for e-mail may add to ISP billings.
FTP
FTP is a special application used for uploading and downloading files to and
from the Internet. Programs like Win-FTP and Cute_FTP offer an easy-to-use
interface for moving files to a remote computer and are popular with
Webmasters. Most new browsers support downloading files via FTP
automatically.
TCP/IP
TCP/IP is the language (network protocol) used by computers to talk to each
other over the Net. TCP/IP has also become a common protocol for LANs.
Regardless of which operating system or software you use, your commands
travel through the Internet in TCP/IP format. The services of the Internet and
the Web could not be provided without TCP/IP.
IP Address
Each machine on a network is given a unique 32-bit address. These addresses
are normally expressed in decimal values of 4 bytes, separated with periods—
for example, 127.0.0.1. Each position can have up to 256 values, from 0 to
255. Without a unique address, there would be conflicts and chaos. It
designates the location of its assigned device (usually an NIC) on the network.
ISPs
ISPs furnish the connection between dial-up (modem) users and the Internet.
Although some are big names with millions of users, there are many more that
serve local areas with both dial-up and hosting plans.
URLs
As mentioned, the URL is the Web's address system. To access a Web site, the
user must enter the designated URL on the network. Each URL begins with the
character sequence http://. The letters HTTP are an acronym for the Hypertext Transfer Protocol, which identifies the Web site as an address. The rest of
the URL is the name of the site. For example, Microsoft's URL is
http://www.microsoft.com. (Because it is universal, it is seldom necessary to
first type the characters "http://" when typing a URL in a browser; most
engines take it for granted.)
Domain
An Internet domain is a site with a common general interest or purpose, often
run by a single firm or institution. The domain suffix gives a general idea of
the site's purpose: .com for businesses, or .edu for educational institutions.
The following table lists common Internet domains.
Domain
Description
.com
Commercial organizations
.net
Internet core networks (also used by some Internet-related
enterprises)
.edu
Educational institutions
.org
Nonprofit organizations
.gov
U.S. government nonmilitary institutions
.mil
U.S. government armed services
.xx
Two-letter country code (for example, .ca for Canada, .de for
Germany)
NOTE
There are several new extensions being added to Web domain
names, and the above list is not intended to be a complete listing.
DNS
DNS (Domain Name System) is the hierarchical naming system used for
identifying domain names on the Internet and on private TCP/IP networks.
DNS maps DNS domain names to IP addresses, and vice versa. This allows
users, computers, and applications to query the DNS to specify remote systems
by their domain names rather than by IP addresses.
DNS Server
A DNS server is a computer that does the job of matching names and
addresses in the DNS system.
Getting Connected
These days, many computer professionals are involved in getting their clients
online. Before actually setting up the system, you need to determine just how
the computer will access the Internet. Once that was as simple as choosing a
modem. Today that job has become a bit more complicated with the advent of
faster alternatives to POTS. If the customer is planning to use ISDN, then you
will need an ISDN TA. DSL (Digital Subscriber Line) satellite and cable
connections will also require special hardware. Some connections, such as DSL
and cable, may be "always on," meaning that the computer is constantly
connected (when the computer is on). Most modem and ISDN customers make
use of dial-in service, and a connection is only active when the user opens an
application that accesses the Internet. One practice that is becoming more
common is adding a firewall between a computer and the Internet to improve
security. A firewall may be another computer or a stand-alone device that acts
as a gateway to the Internet, monitoring incoming traffic. It can help prevent
the introduction of a virus or attempts to "hack" into the protected system or
network. Firewalls have long been employed in network environments.
Most people use a dial-up connection to the Internet via independent ISPs that
provide local community-based service to users, but popular national ISPs such
as The Microsoft Network (MSN) are useful if you travel because many of them
have toll-free numbers for dial-up access or many local numbers throughout
the country. Local ISPs are appropriate for customers who are looking for a
cost- effective company that offers local (including technical) support.
You also need to consider which browser(s) to set up to "surf" the Internet.
Most ISPs (especially local ones) provide only the connection or gateway to the
Internet. Others provide their own browser software package. Most ISPs allow
you to use your choice of browsers. Some local and national ISPs provide
startup software that includes their recommended browser, as well as FTP tools
and other Internet utilities. From time to time, Web surfers will encounter
pages that work well only with a specific browser or with a specific plug-in like
a Flash! player. In this case, it might be necessary to install additional
software or more than one browser.
Using Ping
Anyone installing or troubleshooting an Internet connection should be familiar
with using the ping (Packet Internet Groper) application. This utility lets you
test the connection between devices using the TCP/IP protocol. When you use
ping, it sends a request to a specific IP address and reports whether the target
is present and how long it takes to get a reply. Figure 15.6 shows ping in
action.
Figure 15.6 Using ping to test TCP/IP connections
Under Windows this program can be run in a DOS window accessed by typing
command in the Run dialog box. The syntax is ping -switches address. For
example, entering ping -t 12.12.122.255 would search for and ping TCP/IP
address 12.12.122.255 until you press Ctrl+C to end the action because you
set the -t switch. The following table shows the switches for the ping
command.
Switch
Function
-a
Resolves addresses to host names.
-f
Sets a "Don't Fragment" flag in outgoing packets.
-i
<TTL>
Specifies the Time to Live for outgoing packets.
-j
<hostlist>
Loose source routing along host-list.
-k
<hostlist>
Strict source routing along host-list.
-l
<size>
Sends packets to the size set in the brackets.
-n
Sets the number of echo requests to the value given within the
<count> brackets.
-r
Records the route for count hops.
<count>
-s
Time stamp for count hops.
<count>
-t
Pings the specified address until stopped. You can view
statistics and then continue pinging by pressing Ctrl+Break.
Stop completely without statistics by pressing Ctrl+C.
-v
<TOS>
Specifies type of service.
-w
Sets the length of the wait periods (in milliseconds) for a
response before showing a timeout error. You may need to set
this if the host is slow in responding.
Lesson Summary
The following points summarize the main elements of this lesson:
The Internet is a vast collection of network servers.
The most active portion of the Internet for the average user is the Web.
The Internet offers a variety of services, and most can be accessed
through a browser.
Most users make use of a dial-up connection provided by an ISP to access
the Internet.
The Internet uses the TCP/IP protocol and DNS to route traffic.
Ping is a useful program for checking TCP/IP connections.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Modems convert parallel digital data to and from serial analog data.
Modem speeds are based on bps.
CCITT (now ITU-T) establishes standards for modem communication.
AT commands are used to manually communicate with and test a modem.
Modems can be installed internally or externally.
The primary modem problem is IRQ conflicts.
The Internet is a vast ad-hoc computer network.
The most active portion of the Internet for the average user is the Web,
but many other services are available as well.
The Internet gateway most people use is a dial-up connection and a
browser.
The Internet uses the TCP/IP protocol and DNS to route traffic.
Any technician who services an Internet connection should understand
how to use the ping utility to check TCP/IP connections.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. What is the purpose of a modem?
2. Which AT command is used to take the phone off the hook?
3. What is the difference between baud and bps?
4. What is the name of the chip that converts data from parallel to serial?
5. Name three transfer protocols.
6. What is Zmodem? What are its advantages over other protocols?
7. Define handshaking.
8. What are AT commands and how can a computer technician use them?
9. Explain the difference between half-duplex and full-duplex. What makes
them different? Where or when is each used?
10. What is the difference between synchronous and asynchronous
communication?
11. Why are fax standards different from modem standards?
12. Describe the Internet.
13. What is needed to set up an e-mail account?
14. What is a browser?
15. What does HTTP stand for?
16. What is the ping command used for?
17. What is a DNS server?
18. What is an ISP?
Answers
3 4
Chapter 16
Operating System Fundamentals
About This Chapter
In this chapter, we shift our attention from the realm of hardware to the
software that lets us put the computer to work. There are literally thousands
of software packages on the market, ranging from productivity tools like word
processors to simple reminder note functions, but the most fundamental type
of software is the operating system.
The operating system provides access to fundamental system services and
allows you to configure hardware features. It is responsible for setting up file
systems and making use of drivers for display adapters, SCSI (Small Computer
System Interface) cards, mouse and keyboard devices, printers, and scanners.
Understanding how to effectively use an operating system is a fundamental
skill for any computer technician.
Before You Begin
You should have already read the material on CPUs (central processing units),
memory, and hard drive operations, and be familiar with the POST (Power On
Self Test) performed every time the computer is turned on. Basic familiarity
with Microsoft Windows is recommended; intermediate or expert-level
experience is not required. You should be able to perform the basic tasks of
navigating the Windows interface, working with files and folders, using a
mouse, and using applications like a word processor. Understanding the
command prompt is also helpful, but not required.
3 4
Lesson 1: Operating System Basics
All operating systems share certain basic features and elements.
Understanding the inner workings of operating systems is a fundamental job
skill for any technician. In this lesson, we examine the development of DOS
and the evolution of Windows. We also discuss the basic capabilities operating
systems must provide to make full use of system hardware components.
After this lesson, you will be able to
Define an operating system
Explain the fundamental roles the operating system plays in computer
operations
Understand the development of the PC-based operating environment from
early DOS to modern Windows systems
Estimated lesson time: 35 minutes
The Software Core
Virtually all the time spent working with a computer is spent in the realm of
the operating system. With the exception of a few moments after we turn the
machine on, every keystroke, every mouse click, and every interaction with
peripheral devices is recorded and processed by the operating system. Without
it, we would be unable to use any other programs. Most users pay very little
attention to the operating system, but computer technicians need to be able to
work with it effectively to keep the PC running safely and efficiently. All
operating systems share certain basic components and features. The following
sections describe these key components, their functions, and some basic
considerations in their design and use.
User Interface
The user interface is one of the most important, yet underappreciated, parts of
any operating system. A correctly designed interface allows the user to
interact with the computer, accessing its power without having to learn
complicated control methods. Today, the Windows-based environment, making
use of a mouse, a keyboard, drop-down menus, and scrolling content areas, is
the dominant form of user interface.
The majority of Windows-based programs share many of the same commands
for functions like adding and moving text and printing, opening, and saving
files. This common approach saves time and effort, allowing both programmers
and end users to concentrate on the task at hand rather than telling the
computer what they want.
File System Management
The operating system is responsible for creating and maintaining files, placing
them on storage media, reorganizing them, ensuring their integrity, and
erasing them as needed. The design of the operating system determines the
naming convention for files. For example, MS-DOS originally limited the name
of a file to eight characters with a three-character extension following a period
to denote the file type.
Device Management
The operating system does not automatically know the nature of the computer
components that exist on the system. To control hard drives, accept display
information from graphics adapters, or communicate with printers and other
peripheral devices, the operating system must be enabled with drivers and
command sequences.
The operating system needs to provide methods for preparing storage media,
like floppy and hard drives, and to work with its file system. It controls all the
machine's hardware and its functions, tracking the status of communications
ports, printer ports, and remote devices like Iomega Zip drives or printers;
providing memory management; interacting with any TSR (terminate-andstay-resident) programs; and maintaining the integrity of its own operation.
Boot and Installation Routines
Most operating systems are loaded as software. They must include boot
sequence code that can be accessed during system startup so that they can be
loaded into memory and made functional when the computer is turned on.
They must be provided with installation routines as well as troubleshooting
and recovery techniques for reinstallation in the event components become
corrupted during use.
Error-Handling Capability
Problems ranging from severe damage to simple user error can cause a system
to become unstable. A well-designed operating system will be able to detect
such problems, display error messages to alert the user, and provide the
ability to recover without significant loss of data or corruption of the operating
system.
Housekeeping Utilities
A complete operating system includes software routines for defragmenting
hard drives, scanning for viruses, and performing other housekeeping chores
that keep the system running at optimal performance.
Networking Capability
The earliest PC operating systems were designed as single-user environments,
but the increasing popularity of workgroup computing and the Internet has
made built-in support for networking protocols and a collection of
interoperability tools part of any modern operating system.
A Short History of MS-DOS
The newest versions of Windows are advanced operating systems that build on
more than two decades of PC software development, beginning with DOS.
There were other operating systems in use during the first days of the PC era,
such as CP/M, but the original IBM PC, released in 1981, shipped with an
operating system called DOS (disk operating system). It was by far the
dominant operating system until it was supplanted by Window 3.1 in 1992,
and later by 32-bit versions of Windows, like Windows 95 and Windows NT.
Today all popular versions of Windows are 32-bit operating systems.
The modern computer professional must be familiar with MS-DOS because
many concepts and conventions used in Windows stem from its predecessor.
Several fundamental diagnostic routines require knowledge of user command
prompt interaction that will be part of your activities as a computer technician.
These include installing a new operating system, formatting a new hard drive,
checking for low-level hardware problems, and repairing damage from viruses.
In Lesson 2 we examine and work with these programs and the command
prompt interface.
There were once many variations of DOS, some with proprietary labels, but
today, most references to DOS are synonymous with MS-DOS. The following
table provides a thumbnail overview of the history of MS-DOS, showing the
development of features as each new version was released. You can use this
information to get a general picture of the development of the PC operating
system as it matured.
Version Introduced
Features
1.0
August
1981
Distributed on one floppy disk (required 8 KB of
RAM [random access memory]).
1.1
May 1982
Added support for 320-KB double-sided disks.
2.0
Introduced support for hard disks, directories,
March 1983 background printing, and the ability to add device
drivers.
3.0
August
1984
3.1
March 1985 Added networks and file sharing.
3.2
January
1986
Increased support for hard disks larger than 10
megabytes (MB) and 1.2-MB floppy disks.
Included support for 3.5-inch floppy disks.
3.3
April 1987
Added new commands and international support.
4.0
February
1988
Added support for hard disks greater than 32 MB,
the MEM command, and MS-DOS Shell.
5.0
May 1991
Added memory management tools, help, undelete,
unformat, and task swapping. This was the last
version to come with a printed manual.
6.0
Included new features such as MEMMAKER,
multiple boot configurations, Windows Unformat
and Undelete, virus protection, and backup.
March 1993 MEMMAKER is a utility used to modify the systems
CONFIG.SYS and AUTOEXEC.BAT files so that
device drivers and memory-resident programs
take up less conventional memory space.
6.2
October
1993
Included ScanDisk, Microsoft Diagnostics (MSD)
utilities, and enhanced diagnostics.
December
1995
The end of DOS as a stand-alone product. It was
relegated to command-level environments
included with Microsoft Windows 95 and later
editions.
7.0
Understanding DOS
All versions of DOS had several things in common. First, they were built for a
specific class of CPU and computer: The original version of DOS was designed
to provide operating system services for the original IBM PC. That machine
shipped with either one or two floppy drives and had a port for a cassette drive
in the back. The original release of the PC did not include support for adding a
hard drive to the system. As Intel processors increased in power and as the PC
became a more advanced platform, DOS was extended to take advantage of
the new features and capabilities.
In spite of improvements with each new version, MS-DOS was never able to
overcome critical limitations. DOS was designed to work as a stand-alone
operating system, lacking any native networking support. The need to
maintain backward compatibility with early Intel processors forced DOS
developers to contend with the severe memory limitations left over from the
original 8080 design.
In fact, DOS always had the ability to keep within the hardware limits of the
basic PC of its day. That meant a very low memory overhead and a simple user
interface that assumed no more than the most basic display system. All
versions used a command-line user interface and required few files present on
the system to run basic services. The command prompt was a standard part of
PC life during the days of DOS for those who did not use Windows (and very
few people did until the release of Windows 3.1). The user interface involved
simply typing an appropriate command following the prompt in the proper
syntax and pressing Enter.
The command prompt could vary, but the most common form was C:\>
(usually known as the C prompt), where the letter stood for the active drive
and a flashing cursor line indicated that the system was ready to accept a
command. Technicians and power users working on Windows-based systems
still need to be comfortable with the DOS command prompt. As you will see in
Lesson 2, using this prompt is still a fundamental requirement in setting up a
new system or hard drive.
DOS Boot Sequence and Files
MS-DOS includes three core programs that are required to make a drive or
floppy disk bootable and load the operating system into memory:
IO.SYS. The interface between the hardware and the operating system
code
MSDOS.SYS. The main operating system code
COMMAND.COM. The interface between the user and the operating
system code
These three files can be seen as layers, each taking an area of responsibility.
Virtually all operating systems work this way. Because MS-DOS is a relatively
simple operating system, examining its approach provides insights into how
more complicated operating systems function.
IO.SYS can be considered the lowest layer, acting as an intermediary between
the various hardware components and the software environment. MSDOS.SYS
is the middle layer. It not only provides key logic but also basic commands for
opening and closing files, navigating the file system, and other common tasks.
COMMAND.COM provides support for the operating system's direct interaction
with the user, accepting commands and performing the necessary steps for
execution.
Although these three core files would make a system operational, MS-DOS had
limitations. One of the great advantages in the PC design is its open
architecture. No two computers have to be exactly alike, so supporting these
variations means having custom device drivers, memory configurations, and
some way of recognizing and managing exactly what is on each system.
Microsoft developers came up with a simple solution: MS-DOS used two
optional startup files to process custom commands required by the user,
hardware devices, or applications. These files were the following:
CONFIG.SYS. Loads extra hardware and device drivers not built into
IO.SYS
AUTOEXEC.BAT. Loads TSR programs selected by the user and sets up
environment variables such as TEMP and PATH
Windows uses a boot process that is quite similar to DOS (we look at it later),
and some versions can actually use the AUTOEXEC.BAT and CONFIG.SYS files.
Booting the system is a term that originated in the early days of computer
operations, coming from the saying "pulling yourself up by the bootstraps."
Here is a summary of the steps involved and how the core files described work.
1. When power is first applied to the system, the computer performs the
POST, a series of self-checks stored in permanent read-only memory. The
POST code includes instructions that cause the machine to locate and
invoke an operating system if it exists.
2. The ROM BIOS (read-only memory basic input/output system) on the
motherboard looks for an operating system. It checks for the presence of
IO.SYS and MSDOS.SYS. The locations to be checked are defined in the
CMOS (complementary metal-oxide semiconductor) and usually involve
first searching the A (floppy disk) drive and then the C drive.
3. The operating system processes the CONFIG.SYS file (if present on the
boot drive). CONFIG.SYS contains information to configure the system
environment, including special memory management overlays and
hardware drivers.
4. COMMAND.COM is loaded.
5. The operating system processes the AUTOEXEC.BAT file (if present).
AUTOEXEC.BAT loads programs and user-defined settings.
6. If no programs (such as Windows) are invoked by AUTOEXEC.BAT,
COMMAND.COM presents the active-drive prompt and waits for a
command.
The process of starting from a no-power condition is called a cold boot.
Occasionally, a system might require a reset—for instance, when the computer
locks up or runs out of memory. Resetting can be accomplished without
turning off the computer by pressing the Ctrl, Alt, and Del keys at the same
time. This is called a warm boot.
The DOS File System
In MS-DOS, the file was the primary unit of data storage on the computer,
allowing the system to distinguish what represented a single collection of
information from another. Files were organized into directories. File and
directory names were up to eight characters long and files could have a threeletter extension following a period. Names were not case-sensitive, and,
internally, the system made no distinction between uppercase and lowercase
characters in naming conventions. When operating in DOS mode, the same
restrictions apply.
Most DOS users quickly came to understand the basic naming conventions of
the operating system. Several extensions were universally used and a number
of others gained wide acceptance. These naming conventions have carried over
into the Windows environment. The following table presents several
extensions that all computer technicians should be able to recognize and use.
Extension
File Type
Used For/Meaning
.exe
Program/application
Executable files.
files
.com
Program files
Command files.
.sys
System files
To define and configure options.
.bat
Batch files
A text file that can be run to execute a
series of commands or launch programs.
DOS offered a series of options that
could be used to perform a wide variety
of tasks automatically.
.txt
Text files
Plain ASCII (American Standard Code
for Information Interchange) data.
.doc
Document files
Word processing file text with
formatting.
.drv
Driver files
Software that configures a hardware
device.
We return to the command prompt and the programs, functions, and
techniques that migrated into the modern Windows operating systems in
Lesson 2. Next, we explore how Windows came to replace DOS and dominate
the PC market.
The Evolution of Microsoft Windows
Early editions of Microsoft Windows (through Windows 3.x) were not really
complete operating systems, but rather operating environments that used MSDOS as a foundation. Windows was developed to make the computer more
developer- and user-friendly by providing a common GUI (graphical user
interface) that could be shared by all compatible programs. The GUI uses
icons, toolbars, standard menus, and common device drivers to simplify
application development and minimize the time it takes a user to learn a new
product. The addition of the mouse and enhanced graphics displays extended
the reach of the PC into the desktop publishing, education, and graphic arts
markets once dominated by specialized workstations and the Apple Macintosh.
Windows Version 1.0 was released in 1985, providing a graphical interface and
little else. Version 2.0 followed in 1987, and it was popular in the engineering,
design, and graphics and desktop publishing communities. It wasn't until the
release of Windows 3.1 in 1992 that this operating environment became
popular.
This jump in popularity could be attributed to an increasing software base with
applications that overwhelmed the features in the MS-DOS environment:
faster graphics cards and improved memory management. The final, most
well-known, and most used 16-bit version of Windows was Windows 3.11,
released in the fall of 1993.
Microsoft Windows 95 took its name from the year of its release. With it,
Microsoft changed more than the naming convention; it changed Windows into
a full-fledged 32-bit operating system.
All applications written to meet current Windows standards provide a common
user interface, including the following components:
The menu system offers the same basic commands for file, print, copy,
and save operations.
Selecting text or objects with the pointing device or keystroke commands
is done in a consistent manner.
Clicking and dragging mouse functions are the same.
The sides of most application areas provide scroll bars for displaying text
and graphics not currently visible in the window.
Windows can be overlapped and resized to make the best use of the
screen area.
Data can be cut and pasted among applications, and data held in one file
can be accessed and used by another program.
This common approach shortens the user's learning curve for unfamiliar
applications. On a programming level, application developers have access to a
toolbox of Windows routines, so they do not have to reinvent the wheel every
time they want to invoke a menu or dialog box.
The multitasking capability of Windows allows the user to have more than one
application open and switch among them, even cutting and pasting data from
one open window to another. DOS was designed to run on 8086 class
machines, with a conventional memory limit of 640 KB of RAM. Windows
overcomes this restriction by implementing new modes of memory utilization.
You should be familiar with how these modes operate for the exam.
Operating Modes
Early PC operating systems were designed for 8088 processors. As more
powerful CPUs became available, the limits of the 8-bit operating environment
hindered the development of programs and devices that could make use of
more powerful PCs. With the release of 80286 processors, the CPU was able to
address more than 1 MB of RAM, thus breaking the DOS barrier. However, the
market was still dominated by MS-DOS–based programs that worked within
this limit. The release of Windows solved this problem by allowing a CPU to
operate in several modes—thus accommodating both the old and new worlds—
and fostering a whole new market for memory managers to help overcome
configuration hurdles.
Real Mode
The original purpose of Windows was to provide an MS-DOS—based GUI. The
first versions did not include memory-management functions and did not
multitask. They were designed only for starting programs and managing files
while operating within the MS-DOS limit of 1 MB of RAM. Later versions moved
outside the 1-MB limit but continued to support this MS-DOS mode until
Windows 3.1 appeared.
This MS-DOS mode, called real mode, is now virtually obsolete. However, some
older MS-DOS applications and hardware still require the use of real mode.
Support of real-mode applications and hardware is part of downward
compatibility. Even in the Windows 95 and Microsoft Windows 98
environments, you will encounter terms, such as real-mode driver, which refer
to operating at this level.
NOTE
If any real-mode drivers are loaded in 32-bit versions of Windows,
the system will be forced into compatibility mode. This will slow
down the machine and limit memory utilization. In general, you
should stay in 32-bit mode.
Standard Mode
Windows 2.0 broke free of the MS-DOS 1-MB barrier by making use of the
286-level protected mode of operation. Protected mode Windows could address
up to 16 MB of RAM. Although MS-DOS programs could run only in the first
megabyte of memory, specialized programs were written that would run in
(and only in) the extended memory controlled by Windows. The term protected
mode refers to the use of protected memory. (Standard mode is run with the
processor in protected mode.) Along with Windows protected mode came the
now-famous General Protection Fault (GPF). Encountering this error generally
means that some portion of the Windows protected mode has been violated
(for example, the program is trying to write data outside the portion of
memory allocated to it).
Microsoft expanded the concept behind Windows by adding support for
standardized graphics, fonts, I/O (input/output) devices, and memory
mapping. Together these elements are known as resources, with Windows
acting as a resource manager. In the MS-DOS environment, application
developers handled these tasks themselves. Because Windows has these
resources built in, it is an easy environment in which to write programs. By
breaking the MS-DOS barrier (engaging 286 protected mode), Windows
running in standard mode takes control of many of the hardware functions.
This means that programs do not have to write the code directly to control
devices; instead they ask Windows to use them.
MS-DOS programs can run only under Windows in real mode. Running 286
protected mode worked well for the special programs, but once in protected
mode, it was not possible to return to real mode without resetting the CPU
(only the CPU—not the computer). The MS-DOS program would unload when
the user switched back to Windows. These versions (1.0 and 2.0) of Windows
could run only one MS-DOS program at a time.
Windows Runtime Version
Certain applications (like Aldus PageMaker) could be purchased with a runtime
version of Windows. This allowed a program that required a Windows
environment to run on a computer that did not have the full version of
Windows installed.
386 Enhanced Mode
Introduced with the Intel 80386 CPU, the 386 protected mode allowed
addressing up to 4 gigabytes (GB) of memory, supported virtual memory, and
allowed multiple MS-DOS programs to run simultaneously. Beginning with
Windows for Workgroups 3.11, only 386 enhanced mode operation allowed for
use of the operating system's features. Real mode was still used in a limited
way for advanced diagnostics and development, but this method of operation
restricts the system's performance dramatically.
Windows Resource Management
As mentioned, Windows is a resource manager, and it treats everything in the
computer as a resource. Resources include memory, video, serial ports, and
sound. All resources are presented to Windows through device drivers, files
that establish communications between a device and the operating system.
Applications are resource consumers that must request access to any resource
using standardized subroutines called the application programming interface
(API). Another file called a dynamic-link library (DLL) can address the Windows
core directly. These small files store subroutines that either come with the
compiler that created the application or are created by the programmer. DLL
files always end with the extension .dll. Loss or corruption of DLL files will
cause an application to lock up or be prevented from loading.
NOTE
Some programs come with custom versions of DLLs that overwrite
the standard DLL of the same name. If a problem occurs after
loading a new application, installing a repair update of Windows
might correct the problem, but this can also render the new
program useless. In such cases, you will need to consult with the
program vendor or check the Microsoft Knowledge Base at
http://search.support.microsoft.com/kb/c.asp for more information
on a fix.
When a program starts, it loads a small piece called a stub in conventional
memory. This stub makes a request to the operating system for RAM (usually
through a file named KRNL386.EXE), which then allocates the amount of RAM
as long as it is available. This area of RAM is known as a segment, and its
location is stored in a heap. Once loaded, a program can ask for resources as
required. As long as there are resources available, Windows will provide them.
RAM is the most important resource that Windows must manage. Windows
provides a way to gain memory when there is none using virtual memory, the
ability to make something other than RAM chips hold data. Windows can create
a special file (called a swap file) on the hard disk drive to act as a "virtual"
RAM chip. Although this allows Windows to access additional resources, the
hard drive is much slower than actual RAM. To compensate for this difference
in speed, Windows prioritizes programs and caches the less frequently used
ones to the slower hard drive, thus allowing the most active program to use
the speedier RAM chips.
To get around the problem of resetting the CPU to run an MS-DOS program,
later versions of Windows have the ability to run what is known as virtual
8086 mode, an extension of 386 protected mode that allows for the creation of
virtual 8086 machines. A virtual 8086 machine is a segment of RAM that
operates as if it is an 8086 computer. Windows will run itself in one virtual
machine (VM) and allocate another VM to an MS-DOS program. Using several
VMs, Windows can overcome the limitations of running only one MS-DOS
program at a time.
Windows for Workgroups 3.11
Microsoft Windows for Workgroups was an upgrade to Windows 3.1. It works
and runs like Windows 3.1 with a few enhancements, such as better
networking capabilities for sharing files and printers. It also includes two utility
programs: Schedule+ and Mail Service.
Windows 95, Windows 98, and Windows Me
Unlike earlier versions of Windows, Windows 95 became a true operating
system in its own right. In addition, Windows 95 ushered in the era of Plug
and Play technology, which allows the operating system to detect new
hardware automatically. These versions of Windows overcome the limits of
DOS and the 640-KB memory limits, can easily be networked, make use of the
Internet, and are aimed at the home and general office markets. Windows Me
is the most recent mass-market edition of the Windows 9x family and offers
improved reliability and recovery, enhanced Plug and Play support, and
extended multimedia capability.
Windows NT
In 1993, Microsoft released another operating system aimed primarily at the
professional scientific, engineering, and design markets. When it was first
introduced, Microsoft Windows NT was used in relatively simple network
installations. Over several revisions, it has been enhanced to support the
needs of corporations ranging in size from small to large and, more recently,
the needs of the Internet and intranets.
Windows NT Workstation is aimed at the technical and professional user, while
the Server editions are designed for robust networking. Both provide high
security levels not available in other Windows operating systems. There are
several versions of Windows NT, ranging from 3.0 through 4.0. In addition,
there are Service Packs, which provide inline fixes that do not change the
version number. Windows NT provides three levels of operating systems in
each of the later versions:
Professional (replaces Workstation). A powerful, robust operating
system with limited networking to allow the professional user to share
printers and files.
Server. A complete LAN (local area network) host with a variety of
sophisticated features for managing users and access to printers, files,
RAID (redundant array of independent disks) installations, and other
shared resources.
Advanced Server. The enterprise edition includes all the tools in the
Server edition, as well as additional tools for complex network
environments.
Windows 2000
Microsoft Windows 2000 is the replacement for Windows NT, adding Plug and
Play support, better multimedia tools, and advanced Internet support. Like
Windows NT, it comes in three versions: Professional (replaces Workstation),
Server, and Advanced Server. It dramatically improves Plug and Play support,
multimedia capabilities, and management and networking tools.
NOTE
Be careful when upgrading to Windows NT or Windows 2000. They
are not merely more powerful versions of Windows 98, but more
robust, completely new environments. Not all applications and
hardware are compatible with them. Be sure to consider all the
advantages and disadvantages before making the decision to
upgrade. Check the Microsoft Web site at
http://www.microsoft.com for the latest version of the
compatibility list.
Lesson Summary
The following points summarize the main elements of this lesson:
An operating system provides the interface between hardware and user.
MS-DOS was one of the first operating systems and was, for a long time,
widely accepted as the standard.
MS-DOS had some major limitations, especially in memory handling and
user interface design.
Early versions of Windows were operating environments that ran on top
of MS-DOS.
There are three files that make up the core operating system of MS-DOS:
IO.SYS, MSDOS.SYS, and COMMAND.COM.
Windows has progressed into a variety of products that offer full access to
the features and power of the modern PC, as well as easy networking and
a common platform for application design using a standard GUI.
Windows still uses several DOS programs and the command prompt for
several key operations.
3 4
Lesson 2: The Command Prompt and DOS Mode
Operations
The command prompt was the familiar PC user interface during the days of
DOS. It still plays an important role in the life of a technician, even in the
Windows era. This lesson covers the key skills needed to use it effectively.
After this lesson, you will be able to
Explain the role of the command-line interface
Be familiar with key DOS terms
Use the primary command prompt applications
Understand the functions of CONFIG.SYS and AUTOEXEC.BAT
Estimated lesson time: 60 minutes
Lesson 1 presented the basics of operating systems—what they are and what
they do. It also provided a summary of the development of mainstream PCbased operating systems: MS-DOS and Windows. This lesson takes us one step
further, into the realm of configuring an operating system and using core
applications to maintain the system and investigate its performance using
command-line applications and tools. It is not intended to be a complete
course in command-line operations or all the fine points of the applications
that are available from it. Both are well beyond the scope of this book.
NOTE
Bookstores and computer and software stores offer books that
describe the various software operating systems. A reference book
for each operating system that you work with is a necessary
component of a computer technician's library. Microsoft also offers
comprehensive documentation on its products, including updates,
troubleshooting issues, and so on, as subscription programs.
The COMMAND Command
MS-DOS, like UNIX, used a command-line or text-based user interface. This
means that the user must memorize and type commands to interact with the
operating system—not exactly a user-friendly operating system, and part of
the reason for the popularity of Windows and its graphical interface. The latest
versions of the Windows operating system still incorporate a limited version of
DOS, which can be either used as a stand-alone environment or run within a
window.
There are some advantages to the simpler text-based interface. It requires no
fancy drivers; the display functions are built right into the system hardware.
Running in DOS mode eliminates the need for 32-bit drivers and high memory
management. That makes it an excellent tool when troubleshooting an ailing
PC. When Windows fails, using the command line (often referred to as going
into MS-DOS mode) is often the best way to access any recoverable data and
begin the repair process. Computer professionals should know how to use and
navigate in the DOS environment.
NOTE
During the course of this lesson, you are encouraged to actually
try using the command line and running many of the examples.
For that reason, we recommend reading this chapter in front of a
PC. We assume you are using some version of Windows when we
walk through an exercise. Keep in mind that some of these actions
can alter the system, so be sure you understand any cautions
given in the text and how the command will operate.
In Lesson 1, we looked at the three core files necessary to load MS-DOS on a
system. COMMAND.COM contains the code that provides the actual user
interface. By running this command under Windows, you open up a DOS
session. You can do that now (regardless of the version of Windows you are
using) by going to the Start menu, selecting Run, and typing command. A
DOS window should open on your desktop with an active prompt.
Type the command mem. You can use uppercase, lowercase, or mixed case;
DOS commands are not case-sensitive. The result should look somewhat like
the example in Figure 16.1, an illustration that shows how the command
interface works.
Figure 16.1 The command prompt and MEM application
The basic concept of command interface operation is quite simple. You type in
a command, and when you press Enter, the operating system loads and
executes the command. That's exactly what happens, as shown in Figure 16.1.
The information displayed on the screen shows the memory usage of the
current system configuration. It was obtained by the memory command
MEM.COM. Once the program has executed, the prompt with a blinking cursor
reappears. It shows where characters will appear when you type them and
indicates that the system is ready to accept a command.
You can modify the appearance and information presented by the command
prompt in several ways to meet your personal preferences and needs. Working
with this feature will help you understand how the command interface works
and make you more familiar with using it. If you have access to a computer,
you should have it running Windows with a DOS session window open. If you
are running DOS, you should have an active command prompt with flashing
cursor displayed. (The instructions that follow assume that you are working at
the computer.) Provide the information displayed on the screen, if you can, to
make it easy to follow along.
Working with the Prompt
Type the command PROMPT /? or HELP PROMPT, then press Enter (the
syntax varies with the version of Windows or DOS; it's OK to try one and then
the other). Commands are shown here in uppercase to make them stand out,
but you can type them in uppercase, lowercase, or any combination, as DOS is
not case-sensitive. After executing the command, something similar to the
following information should be displayed on your screen (the exact
information will vary with the version of DOS being used):
C:\>help prompt
Changes the command prompt.
PROMPT [text]
text
Specifies a new command prompt.
Prompt can be made up of normal characters and the following special cod
$D
Current date
$G
> (greater-than sign)
$N
Current drive
$P
Current drive and path
$S
(space)
$T
Current time
Press any key to continue . . .
We used the DOS HELP command to find out how to use the PROMPT
command. HELP is an internal command, meaning the user doesn't have to
know exactly where it resides; it is always available when the user has a
prompt. The listing generated when the program executed started by
explaining what the command does. The rather terse reply shows how this
command can be used to customize how the prompt appears and the
information it provides. The next line shows the syntax that must be used to
actually enter the command. In this case, it is the command followed by the
desired text that is to be the new prompt. Do not enter the brackets when you
actually use the command.
The listings given later show some of the special options that can be added to
the text string. The final line in the preceding example, Press any key to
continue, tells you that more information on the command is still coming but
cannot fit on the screen. You must press a key to display the rest of the
information before the system will return an active prompt because the
program has not finished executing.
To show you exactly how this command works and make you comfortable with
the syntax used at the command line, we will experiment a bit. In the
command line type
prompt This is the prompt with the time$S$t$g
then press Enter. Your screen should look similar to the following example:
C:\>prompt This is the prompt with the time$S$t$g
This is the prompt with the time 9:32:22.43>
Here is what happened: The PROMPT command (the first word you typed)
executed when you pressed Enter. The program replaced the exiting prompt
with the text and options you selected. The first word is capitalized because it
was that way in the text string you typed, and DOS will take literally any
character you type and make it part of the new prompt. The $S adds a space,
the $t looks up and enters the current system time every time the prompt
appears, and the $g produces the > symbol.
Try a few more strings, maybe your name with the date, and so on. Once you
feel you understand how the command and the syntax work, change the
prompt by typing the command prompt$P$G (which will give a prompt that
looks like C:\>, where C is the active drive letter), and move on to the next
part of the lesson.
Internal and External Commands
External commands are programs that exist as separate files. To use them you
must already be in the directory where the file exists, or tell the system
exactly where to find the file by typing in the complete path to its location. You
should be familiar with external commands because they are also common to
the Windows environment. DOS mode provides several external programs and
commands.
In Windows, you also have access to a variety of useful applications and
system utilities, such as Windows Explorer, Notepad, System Information, and
the Control Panel. DOS mode has its own collection of management tools—the
internal commands—that are built into the operating system. These include
DIR, the directory command, which displays a list of the files and
subdirectories for the location in which it was requested; COPY, which allows
you to make a copy of a file and move it to another location; and MEM, used
earlier in the chapter, which provides a breakdown of memory use on your
computer. Internal commands can be tied to the command prompt warning
about where the file resides on the system. The following table lists examples
of commonly used internal MS-DOS commands.
NOTE
Keep in mind that the exact options and operation of MS-DOS and
DOS mode under Windows will vary from version to version.
Command
Function
CHDIR or
CD
Changes the directory (for example, cd\word would take you
to the Word subdirectory).
CHKDSK
Examines the file allocation table (FAT) and directory
structure on a drive, checking for errors and inconsistencies
that can keep you from accessing a file. It also locates lost
clusters and can convert them into files for later deletion. It
can also reclaim wasted space.
CLS
Clears the screen.
COPY
Copies files or disks. To copy all files from the myfiles
subdirectory to the A (floppy) drive, the command would be
copy c:\myfiles\*.* a: Note that an asterisk (*) designates a
wild card in DOS. In this case, you are copying all files with
all extensions to the floppy drive.
DATE
Changes the system date.
DEL
Deletes files (for example, c:\del MYFILE.TXT).
DIR
Lists a directory of files.
DIR /P
Views directories one page at a time. This allows you to view
a subset of the directories when you cant see all of the files
on a single screen. (Directories can be quite long.)
DIR /W
Displays wide format in columns: Only the filename is listed,
not size, date, or time.
DIR /W /P
Displays large directories in columns one page at a time.
Compares two disks. The syntax is: a:\ diskcomp a: b: or
DISKCOMP diskcomp a: a: (the computer will prompt you to insert the
second disk to be compared).
MKDIR or
MD
Makes a directory.
PROMPT
Changes the appearance of the cursor.
RENAME
or REN
Renames a file.
RMDIR or
RD
Deletes a directory. This works only if the directory is empty
of all files, including hidden ones.
TIME
Changes the system time.
TYPE
Displays (types) a text file.
VER
Displays the version of MS-DOS in use.
The following table lists examples of commonly used external MS-DOS
commands.
Command
Function
DISKCOPY
Makes a copy of a complete disk. Requires that both the
source and the destination disk have the same format.
EDIT
Invokes the text editor program. This program is useful for
making changes to text files, such as editing CONFIG.SYS
and AUTOEXEC.BAT.
FORMAT
Prepares a disk for receiving files. Places a root directory on
the disk.
FORMAT
/S
Formats a disk as a system disk.
UNDELETE
Sometimes recovers a deleted file; works only if the disk has
not been modified since the file was deleted.
XCOPY
Copies the contents of one disk to another disk. Does not
require both disks to have the same format. (Note that it will
not copy hidden files unless you use the /h switch.)
Command mode is a good bit different from Windows, in which you can click
(or double-click) on an icon to launch a program. In DOS mode, you have to
know the name of the program you want to run and the directory where the
program resides. There is very little information on the screen, and navigation
is much different from within Windows. To use the command interface
effectively, you must understand the concept of path and the syntax for
entering commands and navigating the file system.
DOS Mode Navigation and File Management
The DOS file system uses a tree structure for its directories, which is based on
a concept of root and branches. The primary volume on a drive is called the
root; it can contain both files and directories. Each directory creates another
branch, which can also contain files and directories. A nested directory is a
subdirectory of the level above it.
Strictly speaking, all directories in the DOS environment are actually
subdirectories of the root directory and must be named. The root directory
does not have a name; it is created when you set up the partition(s) on the
drive, and it is represented by a backslash (\). A fully qualified path is the
entire listing of directories from the root to the file. Look at the status bar in
Figure 16.1. D:\WINNT\System32\COMMAND.COM is the full path to the
COMMAND.COM file. System32 is a subdirectory of WINNT, which is a
subdirectory of the root of the D drive.
The best way to become familiar with directory structure under DOS is to
actually work with it. Because DIR is a system-level command, you don't have
to provide the full path to it. Open up a command window, if you do not
already have one open on your desktop. Type dir, and then press Enter. The
result should be similar to the one shown here, which has been edited as an
example.
C:\WINNT>dir
Volume in drive C has no label.
Volume Serial Number is 7CF4-ED00
Directory of C:\WINNT
12/07/2000 06:13a
<DIR>
.
12/07/2000 06:13a
<DIR>
..
09/06/2000 01:45p
16,214 Active Setup Log.txt
02/22/2000 03:47p
161 mmdet.log
12/07/1999 07:00a
50,960 NOTEPAD.EXE
12/09/2000 08:18a
<DIR>
system32
12/07/1999 07:00a
44,816 twain_32.dll
09/02/2000 07:05a
262 wcx_ftp.ini
97 File(s)
4,665,353 bytes
31 Dir(s) 13,901,348,864 bytes free
C:\WINNT>_
DIR provides a wealth of information if you know how to read it. The first two
lines identify the drive for which the directory was requested, and the third
gives the actual location involved. The actual listing of the files is presented as
a table with four columns. The leftmost column shows the date on which the
file was created; the second column gives the system time at which it was
written to disk. The third column indicates if the item is a subdirectory (which
is, in reality, a file that holds other files), and the fourth column provides the
file size and the name of the file. The final two lines display the total number
of files in the directory and their aggregate size in bytes, followed by the total
number of subdirectories on the drive and the number of subdirectories with
the total amount of free space on the drive.
NOTE
DOS does not support Windows long filenames. Some files may
appear truncated, with something like a ~1 used to show the fact
that the filename is actually different—for example, longna~1.doc.
Also be aware that different versions of Windows and MS-DOS will
have listings that may vary from the ones shown in this lesson.
Notice the first two directory listings. Their names seem to be made up of dots.
They are not actually directories but placeholders for navigation. The best way
to see how they work and get practice with DOS mode file operations is to
create a directory and file, then navigate a bit. To do so, perform the following
steps:
1. Change to the C drive, if you are not already logged on to this drive, by
typing C: at the command prompt.
2. Type in cd .. until the prompt shows that you are in the root directory of
the C drive with the prompt C:\>.
3. Next, create a directory named Test. Type md test. MD is the Make
Directory internal command, and test is the name we are giving it. So the
syntax is md [new directory name].
4. Use the DIR command and make sure the new directory is there. Now
type DIR test. The result should look like this:
C:\>dir test
Volume in drive C has no label.
Volume Serial Number
Directory of C:\test
12/09/2000 10:04a
<DIR>
12/09/2000 10:04a
<DIR>
is 7CF4-ED00
.
..
0 File(s)
0 bytes
2 Dir(s) 13,883,142,144 bytes free
C:\>
The DIR command gave the contents of Test because you asked it to by
following the command with the name of the directory.
5. Now change into that directory by typing CD test. CD is the Change
Directory internal command.
6. Type DIR and press Enter. You should get the same listing as the Test
directory in the active location.
The PATH Command
Understanding the DOS concept of path and how to use the command of the
same name is critical to command-line navigation and running applications in
DOS mode. The best way to understand it is by using it. The PATH command
displays or sets a search path for executable files. Here is the syntax for using
PATH:
PATH [[drive:]path[;...][;%PATH%]
PATH ;
Type PATH without parameters to display the current path. Including
%PATH% in the new path setting causes the old path to be appended to the
new setting. PATH ; clears all search path settings and directs the system to
search only in the current directory. The best way to become familiar with the
PATH command is to use it. At a DOS prompt, simply type path. Doing so on a
computer running Windows 2000 Workstation produces the following result:
C:\>path
PATH=C:\WINNT\system32;C:\WINNT;C:\WINNT\System32\Wbem;C:\PROGRA~1\RESOU
Your result will vary based on the way your system is configured. Any
programs in any of the listed directories can be run from any location on the
machine. Any other programs can only be run in their own native directories
or be activated by typing in the full path before the program name. Listings
with the ~ as part of the name, like RESOUR~1, are truncated. The name has
been shortened because DOS mode does not support the long filenames used
in newer versions of Windows. Experiment with the PATH command until you
are comfortable with it, and then move on to the next exercise.
TIP
Use the PATH command to set the active path to include the drive
and directories of any programs you are troubleshooting in
command mode. That lets you run them without changing to that
location or typing the full path. Once the machine is rebooted, the
path will return to its default setting.
Creating a Batch File
To create a new file in your test directory using the COPY command, perform
the following steps:
1. Have a DOS window open. Make sure you are still in the test directory
with the DIR command by making sure the prompt reads C:\TEST>. (If
not, type CD \Test.)
2. Type the following at the command prompt:
copy con newfile.bat
ver
mem
^Z
The ^Z at the end of the list is made by pressing Ctrl while you press Z.
This writes the file to disk. Be sure to press Enter after each line to make
the line breaks. After you type ^Z, press Enter. The system should
respond with:
1 file(s) copied
3. Repeat the DIR command. You should see the test file in the directory of
C:\Test:
12/10/2000
12/10/2000
12/10/2000
07:22a
<DIR>
.
07:22a
<DIR>
..
07:23a
38 newfile.bat
1 File(s)
38 bytes
2 Dir(s) 14,077,116,416 bytes free
4. Now type newfile, then press Enter. You should see the batch file you
just created run, showing first the version of Windows being used and
then the system memory configuration.
5. Type CLS (another internal command) at the prompt; the screen output
will clear and you should be back at the C:> in the test directory
(C:\Test>).
In this exercise, you created a file by typing commands in a plain ASCII file
and giving it the name NEWFILE.BAT. A batch file is a program that will run a
series of existing commands or applications when you enter its name at the
DOS prompt.
Renaming a File
By now, you should be getting comfortable with the command prompt. There
are some additional skills you should have before taking the exam. One of
these is the simple act of renaming the file. The test file we just created
doesn't really explain what it does and it is a bit long. To rename a file,
perform the following steps:
1. Type Rename newfile.bat vm.bat at the command prompt, then press
Enter.
2. As soon as you press Enter, the name of the file should be changed. You
can test this by simply typing vm.bat at the DOS prompt.
The syntax of the rename command should be obvious by now. (You can
also use the shortened ren.) Enter the RENAME command followed by the
original filename, then the new filename. Next, do a little navigation.
3. At the command prompt type CD.. As explained earlier, the directory
listing with the two dots is a placeholder for navigation purposes. You use
it to move up one level in the directory structure.
4. The prompt should now show that you are in the root directory of the
drive. Try running the new file by typing vm.bat. Because you are no
longer in the directory that contains the file and the operating system
does not find it, you should see an error message listing somewhat like
this one:
C:\>vm.bat
vm.bat is not recognized as an internal or external command,
operable program or batch file.
C:\>
The exact wording of the error message will vary based on the versions of
DOS and Windows you are using. Earlier versions will simply show "File
not found." DOS was never known for verbose help or error messages.
5. To run a program or use a file that is not in the current directory, you
must provide the full path to the location of the file when you issue the
command. In this case, you can run your batch file by pointing the
operating system to the test directory like this: C:\test\vm.bat. First
provide the drive letter, then use back slashes (\) to tell a system to
move down into subdirectories, and finally give the full filename.
6. Try it, then clear the screen with the CLS command.
7. Now move back into the test directory, erase the test file, and remove the
new directory to leave your system in the same condition it was in when
you started this exercise. Once again, use the CD command to move into
another directory. Type the following:
cd \test
erase vm.bat
cd..
rd test
dir
When you give the ERASE VM.BAT command, depending on the version of
DOS you are using, you may be prompted to confirm your command. Just
press Y to confirm the operation and continue.
Now run a final directory command to check and make sure that the
action has been completed. The directory should not be in the listing.
Using Edit
At times you may need to edit text files like AUTOEXEC.BAT, CONFIG.SYS,
SYSTEM.INI, or other primary configuration files in DOS mode. You could use
the COPY command techniques employed earlier, but there is an easier way.
All versions of DOS and Windows that you are likely to encounter include a
text editor called Edit that you can use to create and modify text files. Figure
16.2 shows Edit open in a DOS window.
Figure 16.2 Edit, the DOS mode text editor
Any computer technician should be able to operate a basic word processor and
should find Edit quite familiar to use. Because of that, we won't dwell on its
finer points. There are a few things that you should be aware of, however, if
you are not used to the DOS environment:
If the path to the file you wish to edit is not defined, you will have to
enter it to run Edit and display the file you wish to edit.
Unless you have a mouse driver for DOS mode installed in
AUTOEXEC.BAT (or as part of native DOS operation), you will not have
mouse support in Edit. Press Alt plus the first letter of the menu desired
to open a menu, then the cursor keys and Enter to select and use a
function.
We work with additional DOS commands in the next lesson and in Chapter 17,
"Introducing and Installing Microsoft Windows," Chapter 18, "Running
Microsoft Windows," and Chapter 19, "Maintaining the Modern Computer," in
conjunction with very important troubleshooting techniques. The following
table presents a quick reference of some of the important terms and concepts
you should be familiar with when working in DOS mode, as well as for the A+
certification exam. Some items are a review of the previous discussion; some
expand on the material just presented and will be used as we continue.
Term
Description
Backslash
(\)
A symbol used to separate each directory level, for instance
C:\Windows\Utilities. For this reason, it is a reserved
character and cannot be used as part of a filename.
The ability of the operating system to distinguish between
uppercase and lowercase letters. MS-DOS commands are not
Case
case-sensitive. Traditionally, MS-DOS commands have been
sensitivity represented in documentation as uppercase. You can type
MS-DOS commands in either uppercase or lowercase (they
are shown in this book as uppercase).
Cursor
Anytime you are entering data, whether in an application or
in an MS-DOS command, the cursor (usually a small flashing
line) indicates the place where the next character will be
inserted. It is a good idea to always know where your cursor
is.
Default
drive
Each drive in a computer has its own letter designation. The
default drive is the active drive. Unless otherwise specified,
any commands act on the default drive. The current default
drive is indicated by the MS-DOS prompt. For example, if you
want to see a directory (the command is DIR) of files on the A
drive and the default drive is C, you need to type DIR A:.
Otherwise, you will see a directory of the C drive.
Directory
Directoriesknown as folders in the Windows and Macintosh
environmentsare locations for storing files. Every disk
contains a main directory known as the root directory. Below
the root directory is a hierarchical structure of other
subdirectories.
DOS
prompt
The DOS prompt usually displays the active drive letter (for
instance, C) and directory. This indicates that the operating
system is ready to accept the next command. (The prompt is
user-changeable.)
Drive
pointers
DOS assigns letters to each drive during the boot process.
You can type a command and press Enter to execute it. If you
Entering
make a mistake, correct it by using the Backspace or Del
commands keys. Use Esc to start a command again. Press F3 to repeat a
command.
Error
Brief technical messages that are displayed when an error
messages
occurs.
A filename is made up of three parts—a name of up to eight
Filenames characters, a period, and an extension of up to three
(also
characters. The name can include any number, character, or
filespecs) the following symbols (reserved characters): _ ( ) ~ ! % $ &
#. You cannot use spaces in MS-DOS filenames.
Greater
than (>)
This symbol is used to indicate that a command can be
redirected to an output device. For example, to redirect the
directory command to a printer, type DIR > LPT1.
Path
The address to a file. The path consists of the drive name, the
location of the file in the directory structure, and the
filename (for example, C:\Mystuff\MYFILE.DOC).
Prompt
The command promptuser interface provided by
COMMAND.COM to signal to the user that the computer is
ready to receive input (for example, C:\> or A:\>).
Switches
Many MS-DOS commands can be used with a switch (/
followed by a letter) to invoke special functions. Because no
comprehensive MS-DOS manuals are available as part of the
shipping product for versions later than MS-DOS 5, when you
follow a command with a space and /, a list of parameters and
switches available for that command is displayed.
Syntax
Syntax is the arrangement and interrelationship of words in
phrases and sentences. In computer jargon, it is the correct
format in which to type a command. In MS-DOS, every letter,
number, and space has a value. The most common problem
when typing MS-DOS commands is adding or leaving out a
letter or character. Simple typing mistakes are the most
common cause for Bad command or filename errors.
Wildcards
These can be used to expand a search for a file with the DIR
command, and allow the user to locate files of a similar type
or name. The question mark (?) matches any character in a
specified position, and the asterisk (*) matches any number
of characters up to the end of the filename or extension. For
example, to search for files beginning with the letter A, the
command would be DIR A*.* or A?????.* (the second
command would find a file that starts with the letter A and
any other five characters).
Working with CONFIG.SYS and AUTOEXEC.BAT
As mentioned in Lesson 1, the CONFIG.SYS and AUTOEXEC.BAT files can be
used during the boot process to execute commands and load legacy drivers in
many versions of Windows (although their use diminished beginning with
Windows 95). The CONFIG.SYS file is run first. It sets up and configures the
computer's user-defined hardware components. The AUTOEXEC.BAT file
executes commands and loads TSR programs.
NOTE
TSRs were very popular during the heyday of MS-DOS and were
often used to adjust how the operating system used memory. If
these programs improperly adjust the system memory stack or
cause a conflict, they can cause a variety of difficult to isolate
problems. The problem gets worse if more than one program is
being used. In the Windows environment, you should generally
stay away from using TSRs unless they are absolutely necessary.
We cover their operation with different versions of Windows in
Chapter 17, "Introducing and Installing Microsoft Windows," and
troubleshooting in Chapter 18, "Running Microsoft Windows."
CONFIG.SYS Commands
The following table lists several CONFIG.SYS settings and their functions. Keep
in mind that not all settings are available (or recommended) in all versions of
Windows.
Setting
Function
BUFFERS
Allocates reserved memory for transferring information to
and from the hard disk.
COUNTRY
Enables MS-DOS to use country conventions for times,
dates, and currency. Example:
COUNTRY=044,437,C:\DOS\COUNTRY.SYS. (You do not
need to use this in the United States unless you wish to
use an alternate convention.)
DEVICE
Loads a device driver into memory. Example:
DEVICE=C:\DOS\EMM386.EXE
DEVICEHIGH Loads a device driver into upper memory.
DOS
Loads part of MS-DOS into upper memory area. Example:
DOS=HIGH, UMB
FCBS
Specifies the number of file control blocks (FCBs) that MSDOS can have open at the same time.
FILES
Specifies the number of files that MS-DOS can hold open
concurrently. Example: FILES=60
INSTALL
Loads a memory-resident program. Example:
INSTALL=C:\DOS\SHARE.EXE/F:500 /L:500
LASTDRIVE
Specifies the maximum number of drives the computer can
access. Example: LASTDRIVE=Z
MOUSE.SYS
Loads a mouse driver.
NUMLOCK
Specifies whether the Num Lock key is on or off when MSDOS starts.
SHELL
Specifies the name and location of the command
interpreter. The interpreter converts the typed command to
an action. The default for MS-DOS is COMMAND.COM.
SWITCHES
Specifies special options in MS-DOS. The /n switch will
disable the use of the F5 and F8 keys to bypass startup
commands (used for security).
Here is a sample CONFIG.SYS listing:
DEVICE=C:\WINDOWS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE NOEMS
DOS=HIGH, UMB
BUFFERS=20
FILES=80
FCBS=4,0
LASTDRIVE=Z
DEVICE=C:\CDROM\NEC2.SYS /D:MSCD001 /V
AUTOEXEC.BAT Commands
The following table lists several commands that are often used in an
AUTOEXEC.BAT file.
Setting
Function
ECHO
Displays commands as they are executed. ECHO OFF
suppresses the display of commands as they are executed.
PAUSE
Stops the execution of AUTOEXEC.BAT and displays the
message Strike any key to continue.
PATH
Defines the search path for program commands.
SET
Displays, sets, or removes MS-DOS environment variables.
SMARTDRV
Provides disk caching.
KEYB
Configures a keyboard for a specific language.
SHARE
Starts the Share program, which will install the file sharing
and locking capabilities.
DOSKEY
Loads the DOSKEY program. You can use the DOSKEY
program to view, edit, and carry out MS-DOS commands
that you have used previously.
MOUSE.EXE Loads a mouse driver.
PROMPT
Sets the display of the command prompt.
Here is a sample AUTOEXEC.BAT listing:
@ECHO OFF
PATH C:\DOS;C:\WINDOWS;C:\
DOSKEY
SMARTDRV
UNDELETE /LOAD
VSAFE
MSAV
TIP
Here are a couple of useful tricks to try when working with
CONFIG.SYS and AUTOEXEC.BAT. If you want the computer to
ignore a command line, type REM before that statement. For
example, REM MOUSE.EXE would tell the computer to ignore that
line, and the MOUSE.EXE file would not be loaded. Before editing
existing CONFIG.SYS or AUTOEXEC.BAT files, copy them to a
different directory or make a copy of each, but with an .old
extension to the filename (AUTOEXEC.OLD and CONFIG.OLD). This
way, you will have the current configuration data at hand if
something goes amiss.
Lesson Summary
The following points summarize the main elements of this lesson:
DOS mode programs offer tools for working with a Windows system that
is not properly loading the user interface or 32-bit modes and cannot be
repaired using safe mode.
DOS mode is still used for performing low-level disk operations like
partitioning hard drives and running some virus test and recovery
programs.
A+ technicians should know how to navigate in DOS mode and perform
basic file operations.
CONFIG.SYS and AUTOEXEC.BAT are two files that allow custom settings
during the boot phase but are not fully supported (or even recommended)
with some 32-bit versions of Windows.
3 4
Lesson 3: File Systems
One of the most important roles that an operating system plays in computer
operations is defining and managing the file system. This lesson examines the
major file systems in use today. In configuring a system or performing a new
upgrade, it is often necessary to choose the appropriate file system for best
performance, full access to operating system features, system security, data
reliability, and compatibility.
After this lesson, you will be able to
Explain the differences among the major file systems used on today's PCs
Understand why different types of media (magnetic, CD-ROM, and so on)
have different file systems and attributes
Understand how to choose which file system to use on a new hard drive
or floppy disk
Understand file attributes and how they are used
Estimated lesson time: 40 minutes
File System Basics
The file system is a component of the operating system that acts as an
interface with hardware storage devices, and organizes data on them in a form
that can be used by the system and applications. It is not unusual to have
several file systems on a modern PC. Part of the reason for this is that
different types of storage media often require different types of formatting or
translation because of the amount of storage media involved or for compliance
with a standard. For example, the size of a hard disk will limit which file
system it can use, and CD-ROM devices are manufactured with a specific file
system already in place.
The file system defines many things including file naming conventions, file
size, and, in some cases, the capacities of the storage products themselves. In
the case of products like CD-ROMs, digital video discs (DVDs), and Zip drives,
the manufacturer or a standards committee defines the capacities.
Magnetic media like floppy drives and hard disks employ several different
types of file systems, depending on the operating system on the target
computer. Choosing the right operating system is an important step during the
installation or upgrade process.
Key Terms
The following table provides definitions for key words that are necessary to
understand the operation of file systems. Most should already be familiar from
earlier lessons, but a quick review is in order.
Term
Definition
Block
A set of contiguous bits that make up a definable quantity of
information on storage media.
Boot disk
A system device (usually a hard drive, floppy drive, or CDROM drive) that is used to start a computer. Usually, but not
always, this device also contains the operating system code.
Boot
sector
The sector on a disk containing a small amount of information
that defines the devices layout, identifies the file system, and
allows the drive to be declared a boot device.
Cluster
The number of disk sectors that can be treated as a single
object by the operating system.
A hard disk or system that has been configured so that it can
operate using more than a single operating system or file
system.
A method of encoding data, usually to prevent unauthorized
Encryption use, in a form that can be read only by using the decoding
mechanism.
Dual boot
End-of-file This is the last bit of information contained in the file. In the
(EOF)
preceding lesson, when you created a batch file, the Ctrl+Z
marker
character was the EOF marker.
File
Data collected and stored as a single unit on some form of
mass storage medium.
FAT
The linked list system used to track disk space currently in
use. This was the fundamental method used by early DOS
operating systems, and is still available today in several
formats.
File
format
The way the file content is formatted for individual files
within a file system.
File
handle
An integer value set by the file system to denote an open file.
File
locking
A feature in a network file system that allows an individual
file to be locked so that two instances cannot be open for
modification at the same time.
Filename
The identifier used to label the individual file for use by the
operating system or user. Different file systems have
different naming convenions, allowed lengths, and reserve
characters that cannot be used in naming a file.
Folder
The equivalent of a directory that is used to hold a collection
of files in the Windows file system.
Format
The act or program used to prepare a disk for use by a file
system. Also referred to as a high-level format, it requires
that the hardware already be prepared with a low-level
format and be partitioned. This usually involves dividing the
media into a series of tracks and sectors.
Low-level
format
An initial preparation of a hard disk used to prepare the
media for partitioning and high-level formatting by a file
system. Low-level formatting is usually performed using
firmware or software provided by the drive or disk controller
manufacturer.
Master
boot
record
A specific sector on the first partition of the drive containing
executable code and information about the operation of the
start process for a given operating system.
Partition
table
Indicates the logical structure (partitions) of a hard disk.
Partitions are used to divide a large physical drive into
smaller virtual sections. Each section can then be described
as a logical drive and have its own individual drive letter. The
partition table is kept in the same location as the master boot
record.
Primary
partition
The key partition on a hard disk. Most systems only have one
primary partition, which holds the boot sector and operating
system. This volume is usually designated the C drive.
Sector
The smallest storage unit on a disk.
Track
A series of sectors residing on a disk and arranged so that
they lie at the same horizontal distance from the center of
the disk.
Volume
A physical or virtual drive designated on a storage system.
Comparing and Choosing File Systems
There are several file systems commonly used on today's PCs. For most end
users, the operating system of choice is Microsoft Windows, of which several
varieties are available, including Windows 95, Windows 98, Windows Me,
Windows NT, and Windows 2000. All offer two or more options for choosing a
file system. As an A+ technician, you will be expected to help users select the
right operating system, install an appropriate file system, and explain the
differences among them. The actual choice of which file system to use can
involve several factors, as follows:
Is the computer's storage system to be dedicated to a single operating
environment, or will the machine be used for two or more operating
systems?
How many hard drives will be installed on the system?
What are the sizes of the drives to be used on the system?
How large are the expected partitions on the hard drives?
Will the user need to make use of any legacy applications that will not
support one of the newer file systems?
Is the owner interested in using advanced file system features only
offered on newer file systems?
Are there security considerations that require the use of a file system
that provides additional controls over access to directories and files?
FAT-Based File Systems
All modern PCs can use a FAT-based file system. This is a very simple form of
file system, named for the fact that it organizes files by listing them in a table.
A backup copy is maintained, and both are kept in the root directory of the
primary partition. The FAT file system was originally developed for floppy
disks, and all versions of Windows still use FAT for that purpose.
There are three basic varieties of the FAT file system in use today. All start
with the letters FAT, followed by numbers designating the number of bits
required for a single FAT entry. For example, the floppy drive version known
as FAT12 uses a 12-bit table. FAT16 was introduced with MS-DOS 3.0 to
enable support for large drives. FAT32 is the preferred file system for Windows
95 and later versions and supports long filenames.
FAT-based file systems are quite popular and perhaps the most widely used
PC-based file system. Reasons for their popularity include ease of installation,
a wide range of management tools, and compatibility with a wide range of
operating systems including all versions of Microsoft Windows, OS/2, and
many PC versions of UNIX.
FAT16 and FAT32 Compared and Contrasted
Deciding to use FAT and choosing which version to use was simple in the past.
In the days of MS-DOS, FAT16 was just about the only option. FAT32
complicated matters. It offers several enhancements but lacks some of the
broad compatibility of its earlier sibling.
The following table compares the various features of FAT16 with FAT32.
FAT16
Widest range of compatibility with
operating systems, supported by
all versions of DOS, Windows 95,
Windows 98, Windows NT,
Windows 2000 and several
versions of Unix.
FAT32
Limited compatibility with operating
systems.FAT32 for Windows 95
OSR2 (Operating System Release 2)
and Windows 98 are only compatible
with those operating systems.
MS-DOS bootable floppy can be
Cannot use a DOS or Windows 95
used to boot a problem system and
(other than OSR2) disk to boot and
access all files on a viable FAT16
access files on the hard drive.
hard drive.
Small system footprint offers
performance advantages on
volume smaller than 250 MB.
FAT32 allocates disk space more
efficiently than FAT16, allowing the
system to make more efficient use of
disk space. It often allows storing of
much more data compared to FAT16.
Requires manual intervention to
make use of the backup copy of
the FAT if the original becomes
corrupted.
Can automatically employ a backup
copy of a volume's FAT if the master
copy becomes corrupt.
No backup provided of the boot
sector.If the boot sector becomes
corrupt, all data on the volume
may be lost.
Provides automatic backup of the
boot sector, providing a way to
possibly recover the volume in the
event of a boot sector failure.
Individual volume size cannot
exceed 2 GB and still maintain full
compatibility with all supported
operating systems.
Supports drives up to 2 terabytes
(TB) in size; largest volume size is
32 GB.
No version of the FAT file system provides built-in security or data
compression methods.
Offers much better performance if
the system must use real-mode
MS-DOS or Windows 98 operating
in safe mode.
Smaller cluster size can result in
faster load times for applications and
large data files.
Dual boot of DOS and Windows,
Windows NT, and Windows 98 is
possible with FAT16
Dual boot with non-FAT32-supported
operating systems is not supported.
FAT16 is limited in the length of
file names to the 8.3 convention of FAT32 supports long filenames of up
an eight-character name with a
to 255 characters with the ability to
three-character extension and no
use spaces.
spaces
FAT16 volumes can be converted to FAT32 using the Drive Converter
Wizard. Once done, the drive cannot be returned to FAT16 operation.
The NTFS File System
With the advent of Windows NT, Microsoft introduced the NTFS (NT file
system). Like FAT32, it supports long filenames and the use of spaces in
names. Unlike FAT, NTFS is optimized for multiuser environments. It provides
an extra level of file security, and is more reliable than previous file systems.
This technology was improved with the release of Windows 2000. As with the
advances in the FAT system, there are some minor incompatibilities among
versions due to the changes needed to allow for improved features. As a
result, not all file system operations available in the Windows 2000 version of
NTFS can be used when accessed by systems running Windows NT. Microsoft
recommends using the new version of NTFS on all machines running Windows
2000 unless there is some overriding reason to use an alternate file system.
The following lists detail the advantages and disadvantages of the NTFS file
system.
In the Plus Column
NTFS supports very large volumes up to 2 TB in size.
It maintains a log that can be used to recover and repair a volume's
content in the event of a system failure.
The root folder volume can hold an unlimited number of files.
NTFS employs a B-tree file structure resulting in faster file access. B-tree
data structures are often used in database applications, allowing the
system to quickly trace a record or file using a branching algorithm.
The advanced compression systems available on NTFS volumes allow
users to compact individual files and folders and still read them while they
are compressed.
Both folders and files can be set with security levels that define who can
access them, the level of access permitted, and whether or not the file
can be accessed over any network. You can set security levels for
individual users, groups of users, or all users on the system.
An administrator can set disk quotas limiting the amount of space that an
individual user can use for personal files.
In the Minus Column
NTFS volumes are not directly accessible under MS-DOS, Windows 95, or
Windows 98.
NTFS volumes cannot be used as a primary partition for dual boot system
configurations with those operating systems.
For volumes smaller than 400 MB that consist mainly of small files, the
additional overhead required for NTFS features may result in slower
performance than under a FAT file system.
File System Size Limitations
Different file systems are available on PCs developed during different points in
hardware development. As a result, their capabilities relative to hard disk size
mirror the increasing capacity of the hardware at the time the operating
system was released. The following table shows the supported volume size and
default cluster size for the various operating systems. Keep in mind that under
FAT, drives smaller than 16 MB are created using the FAT12 mode. Another
consideration is that MS-DOS, Windows 95, and Windows 98 cannot access
FAT16 volumes larger than 2 GB.
Volume Range
FAT16
FAT32
NTFS
7 MB–16 MB
2 KB
Not supported
512 bytes
17 MB–32 MB
512 bytes
Not supported
512 bytes
33 MB–64 MB
1 KB
512 bytes
512 bytes
65 MB–128 MB
2 KB
1 KB
512 bytes
129 MB–256 MB
4 KB
2 KB
512 bytes
257 MB–512 MB
8 KB
4 KB
512 bytes
513 MB–1024 MB
16 KB
4 KB
4 KB
1025 MB–2 GB
32 KB
4 KB
4 KB
2 GB–4 GB
Not supported
4 KB
4 KB
4 GB–8 GB
Not supported
4 KB
4 KB
8 GB–16 GB
Not supported
8 KB
4 KB
16 GB–32 GB
Not supported
16 KB
4 KB
32 GB–2 TB
Not supported
Not supported
4 KB
As you can see from the data here, the size of the volume to be formatted and
used has a direct bearing on which operating systems are available.
File System Security
Maintaining the security of files on an operating system is another
consideration when choosing a file system. Generally speaking, NTFS offers
significant security advantages over other PC-based file systems. FAT offers
the advantage of less overhead plus greater OS compatibility and may be
better suited when advanced security mechanisms are not needed.
File Attributes on FAT File Systems
FAT was developed without any direct consideration of multiple users on the
system, so designers had no concern about prying eyes. You cannot lock a file
so that it can be kept from anyone who has access to the system. Instead of
passwords and locked files and directories, FAT offers a set of attributes that
provide a method to prevent overwriting files that need to stay in the same
form, to hide files from being shown in regular directory listings, and to denote
if a file has been backed up. The FAT maintains a marker for each file noting
whether or not an attribute is set.
In DOS mode, you can set file attributes using the attribute command. In
Windows, you can adjust attributes by right-clicking a file and choosing the
Properties option from the shortcut menu. The following listing shows the
syntax and options when using the attribute command in DOS mode:
ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [[drive:] [path] filenam
+
Sets an attribute.
Clears an attribute.
R
Read-only file attribute.
A
Archive file attribute.
H
Hidden file attribute.
/S Processes matching files in the current directory (folders)
and all sub directories.
/D Processes directories as well as files.
NTFS File and Folder Security
NTFS uses the concept of permissions rather than attributes to control access
to files and folders contained within the file system. These vary somewhat
from version to version, but regardless of the version, permissions are set
using a dialog box that can be accessed by right-clicking on the file or folder
involved and choosing the appropriate options from the dialog box. Once set,
the permissions apply to both local users and anyone accessing the system
over the network. Figure 16.3 shows the Security tab in the AUTOEXEC
Properties dialog box. It lists the names of the individuals and roles (such as
the system administrator) that have been granted permissions to the file, as
well as the permissions involved. Select options by clicking the appropriate
button.
Figure 16.3 The Windows 2000 AUTOEXEC Properties dialog box's Security tab
The basic options include Full Control, Modify, Read and Execute, Read, and
Write. A more extensive collection of options including who can delete
subfolders, create files within a folder, modify permissions, and take ownership
of a file or directory are included in the Advanced Permissions dialog box
(shown in Figure 16.4), which is accessed from the Properties dialog box by
clicking the Advanced button.
Figure 16.4 The Advanced Permissions dialog box
Lesson Summary
The following points summarize the main elements of this lesson:
Choosing a file system often involves several variables.
The size of a hard drive may be the deciding factor in choosing a file
system.
If the system must support more than one operating system, FAT16 may
be the only option.
FAT-based file systems offer wide compatibility, a small footprint, and
good performance on small drives.
NTFS systems provide much better support for large drives and enhanced
security.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
Operating System Basics
An operating system is the interface between hardware and user.
All operating systems contain several basic features including the need
for a user interface, and the ability to manage memory, files, and
information between the PC and remote devices.
PC operating systems have evolved from a very simple command-line
interface and management of floppy drive storage to a variety of products
that offer full access to the features and power of the modern PC, as well
as easy networking and a common platform for application design using a
standard GUI.
Understanding operating system installation, operations, and
troubleshooting are key skills for a computer technician.
The Command Prompt and DOS Mode Operations
In spite of the advent of new GUIs, knowledge of command prompt
operations is a necessary skill for troubleshooting computer problems.
The command prompt is a basic user interface that accepts a command,
executes that command, and returns control to the user.
There are a number of internal and external commands that are still very
useful in diagnosing and configuring an ailing system.
Edit is an external MS-DOS program that offers the ability to create and
edit plaintext files.
File Systems
There are a variety of file systems, in several versions, available for PC
platform use.
The most common PC file system is probably FAT16.
FAT32 offers several enhancements over FAT16, including support for
long filenames and larger hard drives. However, it is less compatible with
other operating systems.
NTFS offers many enhanced features over other PC file systems, but it is
only compatible with Windows NT, Windows Me, and Windows 2000.
A single PC system can have more than one file system, but care must be
taken in ensuring compatibility and access to files.
There are a number of factors involved in choosing the correct operating
system, including compatibility, hardware configuration, security,
networking capability, and the need for the machine to boot in more than
one operating system.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. What does DOS stand for?
2. What was DOS created to do?
3. Which version of MS-DOS is bundled with Windows 95?
4. Describe the core operating system files used within MS-DOS.
5. What are the two MS-DOS user-definable startup files and their purpose?
6. Which DOS command is used to show the amount of free space left on a
disk?
7. Describe the difference between real mode and protected mode.
8. Which wildcard character can be used to replace a single character in a
search string?
9. Explain the operation of the command-line interface.
10. If a user working in DOS mode types a valid command to execute an
external program and gets the response "File not found," what is the most
common reason for the error message?
11. Your customer wishes to have a machine configured for both the Linux
operating system and Microsoft Windows 2000 Professional. The computer
has only one hard drive. Identify which file system you would recommend
and explain the reasons for your choice.
12. Explain the steps involved in preparing a new hard drive to accept an
operating system.
13. Why didn't the designers of the FAT file system provide a method for
limiting access to files and folders?
Answers
3 4
Chapter 17
Introducing and Installing Microsoft Windows
About This Chapter
This chapter describes the different members of the Microsoft Windows family
and covers both the planning and installation procedures of a Windows
deployment for both Microsoft Windows 98 and Microsoft Windows 2000 as
required for the A+ Certification Exam. It is a prerequisite for Chapter 18,
"Running Microsoft Windows," which focuses on operating and managing these
popular PC environments. To gain the high level of proficiency required of
today's computer professional, you should obtain advanced training in these
operating systems and build a library of references after completing this
chapter.
NOTE
This chapter focuses on the Windows 98 and Windows 2000
operating systems because they are the primary focus on the A+
Exam. Information on Microsoft Windows Me is provided to round
out the discussion, but it is not currently covered on the test.
Some material on Microsoft Windows 95 and earlier versions of
Windows is included because you may be expected to perform
upgrades on computers running these operating systems.
Before You Begin
This chapter assumes you are familiar with the Windows operating
environment and the material presented in Chapter 16, "Operating System
Fundamentals." You should be comfortable using DOS mode and familiar with
PC system components.
3 4
Lesson 1: The Windows Family
In this lesson, we compare the different members of the Windows family from
the end-user Windows 98 to the enterprise world of large-scale servers and
Windows 2000 Datacenters.
After this lesson, you will be able to
Differentiate among the current versions of Windows
Know the basic features, system requirements, intended users, and uses
for the different versions of Windows currently on the market
Estimated lesson time: 15 minutes
The Expanding Windows Family
The first edition of Microsoft Windows was released in 1983. It was actually
little more than a graphical interface for MS-DOS. Over the next dozen years,
Microsoft engineers developed the product into a suite of full-fledged, 32-bit
operating systems. The Windows family of products can be divided into two
categories: Windows 9x versions were offered primarily for use at home and in
small offices, and the Windows 2000 series was developed mainly for
technical, scientific, network, and enterprise applications.
Although end users are often only familiar with the version of Windows loaded
on their computers, as a computer technician you must be familiar with the
entire line of current Windows editions. You must be able to recommend the
correct product to clients and to install and support it. The following sections
provide a quick overview of the Windows operating systems currently on the
market.
Windows 95
Windows 95 was released to the public in the summer of 1995. It represented
a change in naming conventions, as Microsoft moved from version numbers,
such as Windows 3.1, to a naming system that included the date the new
operating system was released. Windows 95 was aimed at the consumer
market, but its ease of use quickly made it popular in the business market as
well. You may encounter two variations of Windows 95, but no new copies of
this operating system are being sold. The original OSR1 version of Windows
95, sold as both a stand-alone product and an upgrade, was the regular,
commercial, off-the-shelf product. The updated OSR2 version, adding new
hardware support, was only offered as an original equipment manufacturer
(OEM) product installed on new PCs. (You couldn't purchase this version
without buying a new computer.)
In general, you should recommend an upgrade to a newer version of Windows
to any customer bringing in a Windows 95 system for service. These more
recent editions of Windows, listed below, offer significant improvements over
Windows 95.
Windows 98
Three years after the introduction of Windows 95, Microsoft released Windows
98. This version of Windows was the first to really take advantage of Plug-andPlay technology. Hardware meeting the Plug-and-Play requirements is
automatically detected and configured by the operating system after
installation. It eliminated the need to set jumpers and memory addresses for
direct memory access (DMA) channels and it added internal support for new
hardware standards including USB (universal serial bus) and IEEE (Institute of
Electrical and Electronics Engineers) 1394.
Windows 98 also introduced a new generation of support tools, including a
maintenance wizard that allows users to schedule automatic execution of disk
defragmentation and other routine, recurring tasks. The System Information
tool makes short work of checking settings, identifying drivers, and tracking
the operation of the computer. We look at these utilities in detail in the next
chapter.
The Internet was growing in importance during the development of Windows
98, and the new operating system closely integrated the browser with the
operating system. It is also possible to tailor the user interface to make it very
similar to browsing the World Wide Web.
Windows Millennium Edition
The most recent edition of Windows designed for home and general office use
shipped in the third quarter of 2000. Once again modifying the naming
convention, the product is called Windows Me. It continues the trend in
Windows development toward improved ease of use, ease of maintenance, and
support for the newest PC hardware.
Windows Me is closely linked with the Internet. Users can elect to have the
system automatically updated over the Internet via the Microsoft Web site.
The System Restore feature makes it just as easy to undo configuration
changes and return a computer to a preupdate condition. Windows help is now
presented in a browser window, and the user interface can be tailored to mimic
browser operation in many respects. The Windows Media Player is now a fullfledged multimedia tool. Local area networking has been simplified with
increased use of wizards for setup of devices like printers and scanners that
can be shared. Internet settings can be copied from browser to browser so that
multiple computers can share the same logon information and favorites.
Microsoft markets Windows 98 and Windows Me as the best platforms for
multimedia, PC gaming, and home network applications. It also offers broader
support for consumer PC hardware and software products. These operating
systems are designed for installation by the average end user. The hardware
requirements are geared to the typical home PC. Given these features, many
network administrators have also chosen to make these platforms the
operating systems of choice for their average network users.
Windows NT
Power users and those using computers for scientific and technical applications
often require more powerful systems than the average office worker. Network
servers require higher degrees of reliability, security, and advanced
management tools. To meet those needs, Microsoft developed another series of
operating systems, calling the initiative New Technology (NT). The result was
the Windows NT platform.
Windows NT is not just an upscale version of Windows 9x. It is a completely
different operating system, designed to offer faster performance, exceptional
reliability, advanced security, scalable performance (multiprocessor, clustered
computing), and the ability to operate with a number of different processor
families (Intel Pentium, DEC Alpha). Today it is available in both a workstation
edition for stand-alone use and a variety of server platforms scaling all the
way from small networks to large enterprise and Web farm environments.
Microsoft released Windows NT 3.1 in 1993, in both workstation and server
editions. Windows NT 3.51 was released in 1995, offering additional security
enhancements and support for POSIX (Portable Operating System Interface for
Unix). This version also offered tools for incorporating mixed networks of
Windows NT and Novell NetWare servers.
Windows NT 4.0, released in 1996, incorporated a user interface very similar
to that of Windows 95. It also extended the range of hardware supported by
the operating system. Until this release, Windows NT lacked a range of drivers
for scanners, sound cards, and similar desktop components. There are still
significant numbers of computers running Windows NT 4.0. The majority of
these installations are servers, and the average nonnetworking technician is
unlikely to be called on to perform major service to this operating system.
Windows 2000
Windows 2000 is the successor to Windows NT (during its early development it
was called Windows NT 5.0). In spite of the name change, Windows 2000 is
built on a solid Windows NT foundation. In many ways, Windows 2000
combines the best of Windows 98 and Windows NT. It offers and extends the
multiprocessor support, advanced security and administration tools, NTFS (NT
file system), and robust network capability found in Windows NT. Like Windows
98, it provides full support for Plug-and-Play installation of new hardware
including USB, IrDA (Infrared Data Association), and IEEE 1394 devices.
Windows 2000 is actually a family of four products that all offer the same basic
features, user interface, and core technology. The basic features and
differences of these versions are
Windows 2000 Professional. Windows 2000 Professional is considered
the desktop version of this operating system. Like Windows 98, it is
designed for the single user. It supports dual CPU (central processing
unit) operations (SMP, or symmetric multiprocessing), file encryption of
sensitive data, automatic system monitoring and advanced
troubleshooting tools, NTFS5 support, and dramatically enhanced mobile
computing capability over previous versions of Windows NT.
Windows 2000 Server. Windows 2000 Server is the entry-level server
platform, replacing Windows NT Server. It extends SMP capability to four
CPUs per machine and adds support for Active Directory services. This is
the Windows 2000 enhancement to the domain technology found in
Windows NT. Active Directory makes it easy to offer network resources
and develop group policies to enable secure sharing of resources like
storage media, printers, and Internet access. Windows 2000 Server is
designed to offer file, print, and Web services in networks that do not
need the more robust features and scalability found in the Windows 2000
Enterprise products.
Windows 2000 Advanced Server. Windows 2000 Advanced Server is a
powerful departmental server product. It provides support for up to eight
CPUs, up to 8 GB of RAM (random access memory), large scale RAIDs
(redundant arrays of independent disks), load balancing, and clustering of
two servers. This platform is designed for high-traffic networks and ecommerce sites, and it is beyond the scope of the A+ Exam and this
training guide.
Windows 2000 Datacenter Server. Windows 2000 Datacenter Server
is the most advanced and robust networking platform offered by
Microsoft. Like all other Windows networking products, it is only offered
through qualified partners who can install and support it. Windows 2000
Datacenter Server is designed for large data warehouses, advanced
scientific and engineering applications, and large-scale Web farms. It
supports four-way clusters and storage area networks. Like Windows
2000 Advanced Server, it is beyond the scope of this book.
System Requirements Compared
As you can see, there are quite a few versions of Windows available. The
preceding summaries provide a good idea of the intended audience for each
product. The server versions of Windows 2000 are aimed at the network
environment, rather than the end user. In all likelihood, the most appropriate
user for most of those products will be the network administrator. Windows
2000 Professional, Windows 98, and Windows Me are all end-user products.
Most users will be quite satisfied with either of the latter two. The more
demanding user will find Windows 2000 more satisfying from a performance
standpoint, but there is a higher price to pay both in the initial purchase price
of the software and in the hardware required to run it effectively.
Understanding system requirements is necessary to help users choose the
right operating environment and to ensure that it runs effectively.
The following table lists the minimum hardware requirements for the versions
of Windows you are likely to encounter as an A+ technician. Keep in mind that
many users will actually need a system that exceeds these requirements
(especially for technical, multimedia, or graphics applications) to run
effectively. Evaluating those needs is a topic for the next chapter.
NOTE
Windows 2000 can run on systems based on processors other than
the Intel Pentium. However, this table only shows the
requirements for Pentium-based systems.
Hardware
Processor
Windows
Windows Me
98
486
DX/66
Pentium 150
300–400 MHz
recommend
for full
multimedia
and video
editing
Windows
2000
Professional
Remarks
Intel Pentium
Pentium 133
processor with
(Pentium II
MMX or
300
equivalent
recommended); required to
will support
take full
dual CPUs
advantage of
multimedia.
All 32-bit
Memory
Disk space
Display
system
CD-ROM
16 MB
32 MB
versions of
64 MB (can
Windows
support up to 4 benefit greatly
GB)
from
additional
RAM.
2 GB with 650
MB free
120 MB
480 MB
VGA with
16 colors
VGA or higher;
SVGA PlugVGA or higher and-Play
monitor
recommended
Optional
CD-ROM or
digital video
disc (DVD);
8X or faster
drive
recommended
Typical
installations
often exceed
twice the
minimum disk
space
required.
Many
applications
need at least
256 colors,
many 24-bit
color modes.
CD-ROM or
DVD; 12X or
faster drive
recommended
Input devices Keyboard and Windows 98-compatible pointing device
Other
Modem, sound card, and additional RAM, plus network
recommended card if the system is to be used as part of a LAN (local
devices
area network)
NOTE
The actual products that can be used to meet the system
requirements for Windows 2000, and especially for Windows NT,
are much more closely defined than those for Windows 98 and
Windows Me. Before making a final purchase selection, clients
should be advised to make sure that a computer or upgrade
component is fully compatible with the operating system. Microsoft
publishes a hardware compatibility list that you can use to verify
that a given product or computer is certified to work with the
operating system. This is much less of a problem with Windows
2000 than with Windows NT, but it is still a necessary precaution.
The information is available on the Microsoft Web site.
Some System Configuration Considerations
How Much RAM Is Enough?
The amount of RAM necessary on any Windows system depends on the user
and which applications are to be run. The system requirements are just a
starting point. Typical Microsoft Office users can usually work quite well with
32 MB of RAM. Moderate users of the COPY and PASTE commands will need to
increase RAM to at least 64 MB. If users require their applications to be a click
away (all running at the same time), they will need at least 128 MB of RAM. In
the 32-bit Windows world, additional RAM always boosts performance.
Processing Power Possibilities
The recommended CPUs in the preceding table are obviously the bare
minimum. Intended use of the computer is the best guide to the appropriate
CPU. For general productivity applications with little or no multitasking, the
minimum processor requirement may suffice. This is especially true if a good
graphics adapter with its own coprocessor is also installed on the system.
Machines slated for use in scientific, technical, and graphics-intensive
applications, or machines intended for multitasking will need more power.
Machines using multimedia applications will benefit from a Pentium with MMX
capability. Remember that adding more RAM often provides a bigger boost
than the next bump in CPU power.
Getting the Picture
A third area for serious consideration during an upgrade or purchase is the
quality of the graphics adapter. The strength of the card's coprocessor and the
amount of RAM on the adapter affect screen redraw speed, the refresh rate of
the display, resolution, and color depth.
Storage Space
The fourth key component in determining true system requirements is the
amount and type of mass storage available. When upgrading an older
computer with a new operating system, make sure that there is enough
storage space for both the new operating system and anticipated upgrades in
application software. New versions of office suites or graphics applications like
Photoshop or CorelDRAW often require much more space than earlier versions.
Key Points to Remember
You can never have too much RAM.
RAM is the key to optimization of Windows.
The simplest and least expensive way to improve the speed and
performance of any computer is to add RAM.
Moore's Law (from Gordon Moore, cofounder of Intel): Processing power
doubles every 18 months.
Parkinson's Law of Data: Data expands to fill the space available for
storage (from the original Parkinson's Law: Work expands to fill the time
available).
Lesson Summary
The following points summarize the main elements of this lesson:
Microsoft Windows is an evolving platform that has replaced MS-DOS as
the principal microcomputer operating environment.
The Windows market can be segmented into two portions: home and
small office, and technical, workgroup, and enterprise.
Windows 98 and Windows Me are the products of choice for the home
environment and business applications where the advanced networking
features of Windows 2000 are not required.
Windows 98 and Windows Me are the best choices for PC games and
multimedia. They offer the broadest support for consumer hardware and
software packages.
Windows 2000 offers enhanced reliability and security and a more robust
environment that provides MSP ability, improved management and
monitoring tools, and scalability from small networks to complex
enterprise information centers.
Choosing the right version of Windows for a given customer or installation
requires knowledge of the intended uses, the skill of the users,
networking considerations, and the target hardware configuration.
3 4
Lesson 2: Preparing for Windows Installation
The preceding lesson provided an overview of the Windows operating system.
Performing a proper installation involves more than just loading the files and
should include proper planning, which is the focus of this lesson. Lesson 3
walks you through the actual setup for both Windows 98 and Windows 2000 in
detail. The best way to work with this material is to actually perform the steps
on a PC as they are introduced. Most readers should have access to the
commercial Windows product. You can also download time-limited versions of
the Windows 2000 Professional and Server from the Microsoft Web site to be
used for training purposes.
After this lesson, you will be able to
Prepare a system for a new Windows installation or upgrade an existing
one
Manage a dual boot configuration
Estimated lesson time: 45 minutes
Planning the Installation
We've all heard the old saying "prior planning prevents poor performance."
That is especially true when it comes to installing a new operating system.
Both Windows 2000 and Windows 98 offer automated setup programs that
take virtually all the pain out of the actual process of transferring files and
configuring system settings. In many cases, the system can be "successfully"
installed by doing little more than running Setup from the distribution CDROM. While you could install Windows in this fashion, and Windows would
probably run, it probably wouldn't run either as well as or reliably as it should.
Installing either operating system (especially if you're installing both) on a
computer requires following a detailed checklist for an optimal and satisfactory
result. The following sections walk through the expanded process before,
during, and after you run the setup routine. Keep in mind that the job is not
finished until the system is properly tuned, all hardware is working properly,
and application software is ready to use.
The task headings that follow work equally well for Windows 2000, Windows
98, Windows 95, and virtually any other operating system. Specific
information for Windows 2000 and Windows 98 is contained under each
heading as appropriate. Some of the tasks are identical; others vary somewhat
to take advantage of the strengths of each platform. Having both compared
side by side underscores the differences and highlights key features of the two
operating environments.
Some platforms are more forgiving than others, reducing the possibility of
problems during installation. An old saying from the early days of advanced PC
operating systems is, "If a computer is running DOS it only proves that the
machine is not on fire." The MS-DOS environment is a very simple design,
without multiple processes running in the background. Today's environments
must monitor the status and memory usage of several programs at the same
time. In general, the more complicated the computer or operating system, the
more care must be taken during installation.
Decide on the Boot Method(s)
Many people are unaware that more than one operating system can run on a
single computer. Computer technicians, however, may be called on to install
two or even three operating systems on the same machine. Both Windows 98
and Windows 2000 support dual boot operation. Each does so slightly
differently, and the exact configuration depends on the operating systems
involved. These might include various versions of Windows 95 or Windows 98,
one or more editions of Windows 2000, Windows NT, UNIX, and in rare cases,
even OS/2.
Dual boot installations require going through all setup steps for an individual
operating system setup, and the complexity of ensuring that one installation
doesn't damage the other, that file systems are compatible, and that all
hardware devices and software required by each operating system are properly
accessible.
Before undertaking a multiple operating system configuration, carefully read
all relevant documentation for each operating environment. Draw up a
compatibility list and make notes on any special requirements. For example,
some operating systems allow a dual boot, but only if they are loaded first or
last. File systems have to work to the lowest common denominator. For
example, you can run a version of DOS or Windows 98 with Windows 2000,
but only if you employ a FAT16 file system on at least part of the primary hard
drive's primary partition. The older operating systems must reside on this
primary partition. You can also use an NTFS partition on the system, but files
there will not be accessible when in DOS or Windows 98 mode.
Windows 2000 Dual Boot Considerations
You can dual boot Windows 2000 with the following operating systems:
MS-DOS, Windows 3.x, OS/2, Windows 95, Windows 98, Windows Me,
and Windows NT Workstation 3.51 and 4.0.
Each operating system must reside on a different disk partition.
In most cases, it is necessary to use the FAT16 file system.
You need to install application software under each operating system on
the computer so that it will be entered in the appropriate registry. You do
not have to actually install it to two locations unless you load it on a file
system that one of the operating systems can't read. When setting up a
dual boot system involving MS-DOS or Windows 95 with Windows 2000
Professional, Windows 2000 Professional must be installed last.
If you are using a dual boot machine in a Windows NT domain or a
Windows 2000 Active Directory network, each operating system must
have its own machine name to be properly recognized on the domain.
Windows 98 Dual Boot Considerations
The C drive must be a FAT16 partition and include enough free space for
the Windows 98 installation.
The two operating systems must reside in different partitions or hard
disks.
Dual boot systems combining Windows 98 and Windows NT are
discouraged because the two operating systems do not use the same
registry settings or device drivers. If you choose to attempt this, you need
to set up all programs twice, separately loading any required drivers.
Dual booting Windows 98 and Windows 95 is not possible because both
operating systems use the same boot file and the second installation will
overwrite the first.
Windows 98 cannot access files on NTFS partitions, and Windows NT
cannot access files on FAT32 drives.
Confirm Hardware Requirements and Compatibility
As mentioned in the last lesson, to ensure both proper performance and
reliability, a computer's system components must meet or exceed the system
requirements of the operating system involved. Minimum requirements are
just that: minimums (and only in the most basic application environment are
they enough to operate efficiently). With Windows 2000, it is also advisable to
choose components from Microsoft's hardware compatibility list. In general,
with Windows 98 and Windows Me, choosing products that are certified to work
with the operating system and display the appropriate certification logo is
sufficient.
Obtain and Perform Updates to Firmware or Components
Before performing an installation, check the system BIOS (basic input/output
system) firmware for devices like graphics cards, SCSI (Small Computer
System Interface) controllers, and any third-party drivers for updates. It is not
uncommon for businesses to update their code to reduce problems or improve
performance. Any updates that do not require the operating system should be
performed before the installation process begins, and drivers should be made
available for those that do.
Choose Between an Upgrade or a Clean Install
During a clean install, an operating system is installed on a hard disk that is
either brand new or has recently been formatted and is currently without an
operating system. An upgrade simply adds new components and updates
existing ones. Each approach has advantages. The clean install ensures that
there is no difficulty with old files and drivers, offering a "fresh start."
Depending on the existing operating system, an upgrade can simply transfer
many of the existing system settings, user preferences, and network
connections to the operating system.
NOTE
Windows 2000 Professional offers a Check Upgrade Only mode in
its setup routine. This lets you perform a dry run on the system
that reports any possible conflicts that might be encountered
during the actual upgrade, including hardware incompatibilities
and software that might not operate correctly under the operating
system.
Record and Obtain Information
The next step in preparation is creation of a written record of the system
configuration and network settings, along with digital copies of configuration
files, a copy of any custom Windows Registry entries, and any other systemspecific or general network information required to make a smooth transition.
The reason for this step should be clear. Although Windows 2000 and Windows
98 offer Plug-and-Play installation, not all hardware will be recognized
properly, and you may be confronted with device conflicts. In many network
environments, you need to know the machine name, domain name, IP
(Internet Protocol) address, printer locations, and so on. With an open
dialogue waiting for data input, you don't want to have to shut down the
machine to obtain the needed information.
If you are performing an upgrade from an existing system, Windows can
actually do that work for you. The Windows 95 Device Manager (accessed by
double-clicking System in the Control Panel) and the Windows NT Diagnostics
tool both offer a feature that lets you print a hard copy of all system settings
including DMA and IRQ (interrupt request), drivers used, and memory
configurations.
Back Up Data and Key Files
Any time a new operating system is added to an existing computer, you should
make a backup of all data files that the user does not want to lose. There's
never a guarantee that the procedure will go smoothly or that data won't be
lost.
It is also a good idea to make copies of any batch files, user profile files (like
Favorites from the Internet browser), and so on, and save them on a floppy
disk so they can be easily migrated to the new system.
Remove or Disable Possible Conflicts and Verify Existing
Settings
Now it's time to eliminate potential trouble spots. Many programs, like
antivirus scans, third-party memory managers, TSRs (terminate-and-stayresident programs), and legacy 16-bit device drivers may interfere with this
program or cause it to improperly configure the system. Be especially careful
of any third-party disk partitioning software.
If you are upgrading from an earlier version of MS-DOS or Windows that has
active CONFIG.SYS and AUTOEXEC.BAT files, remove any unwanted 16-bit or
legacy entries, then leave the files in place. Both Windows 98 and Windows
2000 can use those files to make appropriate listings in their registries.
NOTE
There are variations in just how simple and effective the
conversion of registry and configurations settings is among
different versions of Windows. The process works best when you
are moving upstream in the same product series. Windows 98
usually smoothly incorporates settings from Windows 95, and
Windows 2000 from Windows NT. Windows 2000 is less effective
working with an existing Windows 98 or 95 system. Keep in mind
that although the user interface may seem similar, Windows 95
and Windows 98 employ quite different core technology than
Windows NT and Windows 2000.
Prepare the Hard Drive and File System
At this point, you should have a good idea of the file system configuration,
how much drive space will be needed, and how the disk(s) will be partitioned.
If the primary drive of the operating system is already partitioned using the
desired file system, you can proceed directly to the operating system setup. If
you are installing Windows 2000 and planning on using the NTFS file system,
you can also proceed directly to the Windows 2000 Setup program, which can
be used to partition and prepare hard drives during the installation process.
If you plan on using either a FAT16 or FAT32 file system, and need to either
create or change partitions, you will have to use the Fdisk utility to prepare
the drive. Fdisk is a command-line utility that dates to the early days of MSDOS. Before using Fdisk, be sure to back up any needed data that exists on
the target drive. Any modification using Fdisk immediately results in the
destruction of all data on the partition.
CAUTION
Before using Fdisk, be sure that no third-party disk management
utilities were used to partition the drive. In most cases, these
applications provide translation between the system and the drive
to provide support for large drives that exceed the capability of the
system BIOS. If they are removed, the drive may not work or may
not report all of its capacity. If you suspect the presence of one of
these utilities, watch for messages during system startup or look
for messages that indicate loading of a driver for the translation
software. This does not apply to firmware-level translation like
that provided by SCSI host adapters.
Partitioning a Hard Drive with Fdisk
The Windows 98 and Windows 95 startup disks, along with all versions of MSDOS, provide copies of Fdisk. If possible, use the same version of the program
as the operating system you are installing. (This is not possible with Windows
2000.) The program can be run from inside a DOS command window in
Windows 98, but cannot be operated on the drive that was used to boot the
system. You will most commonly run the program at a regular DOS command
prompt. The complete syntax is
FDISK [/STATUS] /X
/STATUS displays partition information.
/X indicates that it ignores extended disk access support. Use this switch if you
receive disk access or stack overflow messages.
With many versions of Fdisk, if you are working with a hard disk with a
capacity greater than 512 MB, you will be asked if you wish to enable FAT32's
large drive support. Answering Yes enables the 32-bit FAT file system. If you
answer No, the system uses FAT16, which limits partitions to 2 GB, even if it is
a larger drive. Although FAT32 offers many enhancements over the older 16bit mode, as already discussed, it is not widely compatible with other file
system formats.
Fdisk provides several options:
Create a partition or logical drive
Set the active partition
Delete partition or logical drive
Display partition information
Choose drive (on computers with multiple hard drives)
Make sure you are working on the drive you want to modify if there is more
than one physical hard disk on the system. Check the Current Fixed Disk Drive
listing. The first fixed disk is followed by the number 1. A second physical drive
would be noted with the number 2.
It is best to work in a step-by-step fashion when using this utility. Start by
displaying the current partition information and verifying that you're working
on the proper drive. Next, delete any unwanted partitions. This must be done
in a specific order. Start by removing any non-DOS partitions; then remove
any extraneous logical drives in the extended MS-DOS partition. Next, remove
the extended partition, and finally the existing primary DOS partition. For
example, if you wish to remove the existing primary partition, you must work
through all the steps. If you only want to remove one logical drive and an
extended partition, you must perform only the first two steps.
Remember that Fdisk is primarily an MS-DOS utility. Although it generally has
the ability to remove non-DOS partitions, that is not always true, and you may
have to use a third-party product to remove inside partitions.
Once partitions are deleted, you may go through the process of creating a
partition to actually use for the new installation. Once that is completed, you
need to mark one of the partitions as the primary partition. In general, this is
the first partition, which will be the C drive. With some operating systems or in
a dual boot configuration, this may not always be true. Once you have
completed the modifications, the program verifies the disk integrity and
requires a restart of the system.
File allocation table (FAT)-based operating systems require that after
partitioning a drive, the media must be formatted using the Format utility. The
Format program must be compatible with both the version of DOS that you
have used and the operating system to be installed.
With the hard disk and file system prepared, the computer is ready for its new
installation and you can start the setup process.
Lesson Summary
The following points summarize the main elements of this lesson:
Installing a new operating system requires careful planning.
Dual boot machines must be configured to properly support both
operating systems.
Upgrade and optimize all system components before proceeding with
setup.
You should back up all important files and make a record of key system
settings.
3 4
Lesson 3: Installing Windows
With the effort that goes into preparing for an operating system installation, it
might seem that the actual act of running the setup procedure is anticlimactic.
In reality, there are a number of options and custom settings that can be used
during this procedure to make it more efficient and more reliable, and to help
overcome system configuration problems. You can also set several options
based on user preferences for the network environment the machine will
operate in. This lesson covers in detail the setup routine provided with
Windows 98 and Windows 2000. We cover each operating system in turn.
After this lesson, you will be able to
Choose the best method for setting up Windows 98 and Windows 2000
Describe the issues and features with the different types of setup
approaches
Install Windows 98 and Windows 2000
Troubleshoot problems in installation with both operating systems
Estimated lesson time: 75 minutes
Performing a Windows 98 Setup
Running Setup
Microsoft Windows 98 comes in two versions: one for upgrading an existing
version of Windows on the same drive, and another for a new installation.
Both assume that you have already prepared the file system as outlined in
Lesson 2.
Running an upgrade allows you to maintain settings that already exist under
Windows 95, Windows 3.x, or Windows for Workgroups. If you are using one of
these operating systems, you should usually run the Setup program from
within the Windows interface.
If you do not wish to keep any of the current settings; if you are loading the
operating system on a new computer or a freshly prepared disk drive; or if you
are recovering from a failed setup procedure, then you should run the program
from a command prompt under MS-DOS. The necessary files are available on
CD-ROM (preferred) or on floppy disks (special order), or they can be copied to
a network location that is available to the target computer. Keep the following
points in mind:
A CD-ROM drive to be used for setup must be accessible from the DOS
prompt. The Windows 98 startup disk includes drivers needed to run both
typical IDE (Integrated Device Electronics) and SCSI CD-ROM drives. If
the CD-ROM is attached to the system via a sound card, it may not be
able to run Setup.
Except for necessary device drivers, network card drivers, and any TSR
programs needed to actually operate the systems, no other application
should be running when you begin Setup. Be sure to disable any thirdparty memory managers or antivirus programs.
Running Setup over a network will require about 170 MB of storage space
on the server.
If you are performing a new installation and have the full Windows 98
package for use on a new computer, it will contain a Windows 98 startup
disk. If you are using the upgrade-only package, the program will only
operate if you are installing on a machine that already has a recognized
operating system for improved upgrade, or if you have the disks for one
of those operating systems available to prove that you are performing a
legitimate upgrade.
The Windows 98 Setup program is much improved over the version that was
provided with Windows 95. The earlier product required 12 steps, and Plugand-Play technology was in its infancy. It was often necessary to break the
installation routine or restart under Windows 95. That problem has largely
disappeared with Windows 98, which offers much more robust Plug-and-Play
support and a more compact five-step installation.
Making Use of Windows 98 Setup's Command-Line Switches
There are a variety of options available when running Windows 98 Setup in
command-line mode from the DOS prompt that are unavailable when
performing installation from within the Windows environment. The following
list provides most of the switches in alphabetical order along with an
explanation of their function. The syntax is:
setup /[switch]
at the command prompt.
Many of these commands are very useful in recovering a failed installation or
forcing one on a difficult system:
/? Provides help on syntax command-line switches.
/C Don't load the SmartDrive disk cache.
/D Don't use the existing version of Windows for the early phases of
Setup. (Use if problems starting Setup could be caused by missing or
damaged Windows support files.)
/DOMAIN: domain_name This option sets the Windows NT Logon
Validation domain used by Client for Microsoft Networks to the value
given in domain _name.
/F Saves a little memory by prohibiting holding filenames in the local
cache, but Setup runs slower.
/IC Performs a clean boot in some versions of Windows. If this is set and
KeepRMDrivers=1 is not in the registry, drivers are commented out from
the CONFIG.SYS or AUTOEXEC.BAT file. (Commenting out is a way to
prevent a line in either of these files from executing. The system will not
process any line with the letters REM in front of it. This remains in effect
until the next line break, at which point the system will begin processing
the commands again.)
/ID Disables the usual check of the target drive for the minimum disk
space required to install Windows 98.
/IE Skips the Startup Disk screen.
/IF Performs a "fast" setup. Does not notify setup to look up filenames in
the cache.
/IH Runs ScanDisk so you can see the results. Use this switch if the
system stalls during the ScanDisk check or if an error results.
/IL Loads a Logitech mouse driver that supports the Logitech Series C
mouse.
/IM Skips the check of low conventional memory.
/IN Does not run the networking Setup software. Neither the networking
software nor the Networking Wizard screens will appear.
/IQ Skips the check for cross-linked files.
/IR Does not perform an update of the Master Boot Record (MBR).
/IS Skips ScanDisk.
/IW Does not display the License Agreement dialog box.
/IX Does not perform a character set check.
/NF Does not provide a prompt to remove the floppy disk from drive A at
the end of the Copying Windows 98 Files To Your Computer Setup step
(Step 3). Use this switch when installing Windows 98 from a bootable CD.
/NH Does not run HWINFO.EXE when running Setup from the Windows
95 user interface.
/NOSTART Copies a minimal installation of the required dynamic-link
libraries (DLLs) used by Windows 98 Setup, then exits to MS-DOS without
installing Windows 98.
/NR Skips the registry check.
/PI Keeps forced configured hardware settings (hardware not using
default settings). Some BIOS requires hardware to have a forced
configuration to work. By default, Setup removes the forced configuration
and some hardware may not work properly after this is done.
/PJ Loads Advanced Configuration and Power Interface (ACPI) by default.
/script_filename Uses a script to install Windows 98 automatically; for
example, setup MSBATCH.INF specifies that Setup should use the settings
in MSBATCH.INF. The full filename must be given and it must be eight
characters long with a three-character extension (8.3 filename).
/SRCDIR Specifies the source directory where the Windows 98 Setup
files are located.
/S filename Load the specified SETUP.INF file when starting Setup.
/T:tempdir Specifies the directory where Setup is to copy its temporary
files. This directory must already exist, but any existing files in the
directory will be deleted.
The Actual Windows 98 Installation Process
As you can see from the preceding list of switches, there are quite a few
options when it comes to installing Windows 98. Depending on the current
state of the computer (operating system, and so on) and the options you
select, the Setup program will present you with a variety of dialog boxes or
prompts during the installation. In spite of the differences, the underlying task
remains the same: to discover the computer's configuration, install the
appropriate files, and return the system to the user with both the operating
system and devices in proper working order. What follows is an overview of
the process.
Confirm the Disk Status
Unless overridden, the first thing Setup does is run ScanDisk. If run from MSDOS, Setup will run the real-mode version of a program. ScanDisk inspects the
directory structure, FAT, and the integrity of the file system. If you are
installing from within a 32-bit version of Windows, the program will also fix
any long filename errors found.
Collect Computer and Setup Information
Once the media have been verified, Setup prompts you to provide several
pieces of information needed before the files can be copied:
It makes the user verify agreement with the end user license provisions.
It prompts the user to enter the product key that verifies that this is a
legal copy of Windows 98. Setup cannot continue unless this is properly
entered. It is usually found on the back of the CD case. In some cases,
the product key step is not required (see Figure 17.1).
Figure 17.1 The Product Key dialog box
It prompts the user for the directory into which Windows 98 will be
installed. Once entered, the program confirms that there is adequate
space for the installation. If unsuccessful, you are prompted to specify
another location or remove enough files so that Setup may proceed.
NOTE
If Windows 98 is set up in a new directory other than the one in
which the preexisting version of Windows was already installed, all
Windows-based applications will have to be reinstalled because
any application-specific DLLs will not be present in the proper
Windows 98 directory. Also during this phase, Windows may offer
the option to save the existing MS-DOS and Windows system files
required to restore the computer to the pre-Windows 98
installation state. This is highly recommended, but requires about
an additional 50 MB of hard disk space.
Once a directory structure has been set up, the next step is to choose the type
of installation to be performed. Four choices are offered. Typical installation
provides a standard set of features most suitable for the computer's
configuration. Portable installation includes options useful for laptop users.
Compact installation provides a minimal set of features. Custom installation
provides another dialog box that lets the installer choose the specific options
to be installed. Figure 17.2 shows the dialog box offering these options.
Figure 17.2 The Setup Options dialog box
Another dialog box appears, requiring the user to enter his or her name and
the company name. When the next button is clicked, the user is given the
option to install or remove optional components from the list of features to be
copied to the disk.
The next dialog box requests the computer name, workgroup, and physical
location of the machine. This name must be unique to the network and can
contain up to 15 characters. Names cannot contain punctuation or blank
spaces. The workgroup name has the same limitations. The computer
description cannot contain commas but can be up to 40 characters in length.
This entry is not needed if the computer will not be attached to a network.
Now the user is prompted to provide the geographic location at which the
computer will reside. This is used to allow Web sites to deliver content based
on the region in which the computer is operated. This step does not occur in all
versions of Windows (see Figure 17.3).
Figure 17.3 The Location dialog box
Create a Startup Disk
This step requires a 1.44-MB floppy disk or two 1.2-MB floppy disks. The
Startup disk contains all the real-mode files, CD-ROM device drivers, and
utilities needed to start the computer in DOS mode, along with a suite of
diagnostic programs. In the event the system uses specialized SCSI drivers or
a sound card to access the CD-ROM drive, you will need to manually copy
these drivers to the startup disk and adjust the CONFIG.SYS and
AUTOEXEC.BAT files for proper operation. The Windows 98 Startup disk should
be considered a critical part of your technician toolkit, and understanding its
operation is required for both your day-to-day work and for taking the exam.
We cover it in detail in Chapter 18, "Running Microsoft Windows."
File Copy
This stage is when the actual files are extracted from their compressed archive
files (noted by a .cab extension) and copied to the hard drive. There is no need
for user input during this part of the process.
CAUTION
You should not interrupt the copy process for any reason. If the
procedure does not finish normally, the operating system will be in
an unstable state and you may have to repeat the process.
Tuning the Configuration
Once the copy process is done, the computer will be restarted. At this point,
Windows goes through a tuning process to set up the system based on the
devices found on the computer and any settings migrated from a previous
installation of Windows. The program finalizes the Control Panel and Start
menu and asks the user to select the proper time zone. Once the process is
finished successfully, you will see the Welcoming dialog box, which offers
access to information about the features of Windows 98 (see Figure 17.4).
Figure 17.4 The Welcome To Windows 98 dialog box
Establish Network Connections
If you have installed Windows 98 over an earlier version of Windows that was
already set up on a network, the appropriate network settings and protocols
should already be loaded. When Windows reboots after Setup is complete, you
should see the appropriate network logon. If you installed Windows into a new
directory or performed a clean install, you will have to use the Control
Panel/Network setting to install protocols and configure the network settings in
order to make the computer a part of the network.
Troubleshooting a Windows 98 Installation
If you follow the detailed planning steps covered earlier in this chapter, the
majority of Windows 98 installations will execute properly and the system will
be ready for use after the Setup routine is completed. However, things don't
always go as planned. As a technician, you need to have an understanding of
what the routine is doing behind the scenes, and know how to troubleshoot a
failed installation. At several points the Setup routine examines the system to
determine the hardware and Windows-related software already installed. It
generates several files that track the actions taken, creating logs that can be
used if either automatic or manual intervention is necessary.
Using Safe Recovery
Safe Recovery is a process built right into the Windows 98 Setup code. During
the entire installation, Windows is tracking virtually every action taken. This
information is used if Setup fails in a way that prevents the operating system
from loading successfully due to hardware conflicts, software conflicts, failure
to meet system requirements, system shutdown during the copying process, or
a component failure. Given the wide variation in system configurations, the
failure could be due to any number of reasons. Fortunately, automatic Safe
Recovery often resolves the problem.
Running Safe Recovery is very simple. If you are sure that Setup has hung the
system (there are some components that take a good bit of time to identify
and configure; the system may be busy, or not stopped), wait an additional
three to four minutes, then press Ctrl+Alt+Delete to restart the computer. If
this does not reboot the system, turn off the computer's power, wait ten
seconds, and turn the unit back on. Let the boot process continue normally.
You may be returned to Setup and offered the Safe Recovery option. If so,
select it and proceed with the installation. If not, run Setup again and select
the Safe Recovery option when it appears.
NOTE
If you fail to select Safe Recovery when offered the dialog box,
Setup will repeat the entire Windows 98 Setup process.
Most setup failures are due to hardware detection and system or software
configuration problems. To get around them, Windows uses an iterative
process. When a fatal incident occurs, Windows logs the point of failure and
bypasses the point at which the failure occurred. This method allows Windows
to continue the installation, even when a system has a problematic device.
Windows disables the problem product, so it may not show up as properly
identified in the Device Manager list. You may be able to make the offending
device operational by accessing Device Manager from the Control
Panel/System icon and changing the settings manually. If Setup hangs again,
repeat the process. If the problem is software-related, the Setup Wizard may
suggest removing the software product that is causing problems. In extreme
cases Safe Recovery may not be able to fix a problem, and a dialog box will
appear telling you that Setup cannot continue. If the message offers a
suggestion of the problem's cause, remove the device or software from the
system and start Setup from the beginning.
Beyond Safe Recovery
Sometimes Safe Recovery is not sufficient and manual intervention is
required. In such cases, you should first review the planning process to make
sure no critical issues have been overlooked. If your system meets all
requirements stated by Microsoft and there are no obvious problems, the
information generated by the failed installation can help you pinpoint the
problem. To use it, you must understand both the Windows hardware detection
process and the recovery files generated during installation.
Setup attempts to detect devices that are already installed on the computer
when Windows is added to the system. For devices that support the Plug-andPlay initiative, an interactive set of queries is used to identify both the product
and its required resources. These devices can include everything from the
motherboard, CPU, and BIOS, to display adapters, mouse, and network
adapters.
Older devices that do not support the Plug-and-Play initiative are also
investigated. Memory addresses, DMA channels, and IRQs are cataloged.
During this process, Windows 98 examines device information and settings
from files like WINDOWS.INI and CONFIG.SYS. Buses (PCI [Peripheral
Component Interconnect], SCSI, and so on) and hardware devices are grouped
into classes and listed in the Registry.
Four classes of devices (CD-ROM adapters, network cards, SCSI controllers,
and sound cards) are detected using a process known as safe detection. Safe
detection uses a variety of methods to locate devices that exist on the system
within those classes. It can also investigate ROMs for manufacturer
identification. During Setup, you can opt to skip certain classes of devices. This
is useful if you know a product will cause problems.
The Setup Log Files
The installation routine creates five files that can be used if the process fails:
BOOTLOG.TXT, DETCRASH.LOG, DETLOG.TXT, NETOLOG.TXT, and
SETUPLOG.TXT. As you can tell from the file extensions, most of these are
ASCII files that can be read with a text editor like Wordpad, Notepad, or Edit.
In some cases, Setup actually makes use of these files automatically as it
attempts to recover from a failed installation.
BOOTLOG.TXT is a very useful file for more than just installation issues. It
creates and holds a record of the entire boot process, including which drivers
were loaded and initialized and their status. It is automatically generated
during the setup process, but you can also create it by pressing F8 during a
regular Windows 98 startup, or using the /b switch if you start Windows from a
DOS prompt using the WIN.COM command.
The BOOTLOG.TXT file detects failed initialization of critical virtual device
drivers (VxDs), failure to boot from a SCSI hard drive, failure of a critical
component to load, and the failure to locate a resource. We look more closely
at the options offered with this file in the next chapter.
DETCRASH.LOG is generated if Setup fails during the hardware detection
phase. It contains listings that show which detection module was running and
the resources that were being accessed when the failure occurred. When the
system is restarted, Safe Recovery is invoked and the installation routine
proceeds without any additional attempts to discover that class of device. This
file is used directly by Setup and is not normally readable by the user.
DETLOG.TXT is generated every time the detection process runs, either during
a new Windows installation or by invoking the Add New Hardware Wizard from
Control Panel. It is a user-readable version of the information contained in
DETCRASH.LOG. This file is very useful for a technician, because it can quickly
pinpoint the likely cause of a device that generates an error during
initialization. The following table shows how the entries appear and what they
mean.
Report
Category
Parameters =
"xxxxxx"
WinVer =
Provides Information on
Shows the command-line switches specified when Setup
was invoked.
########
Shows that environment detection is run.
AvoidMem =
#####h#####h
Shows the UMB (upper memory block) address range
specified to be avoided during the detection phase (if
entered)— for example, AvoidMem=c4000-c800
DetectClass:
Skip Class
Media
Indicates that detection found no hints that the computer
might have a particular class of device present, so it
skipped that class.
DetectClass:
Override
When one or more skip class entries appear in
DETLOG.TXT, the Analyzing Your Computer screen is
presented during Setup to allow a manual override of the
decision. Related DetectClass Override lines appear in
DETLOG.TXT for the classes checked.
Custom Mode
Describes your selection for the devices the user told
Windows 98 not to detect.
Devices
Verified =
Shows the number of devices verified from the Registry.
If the number is 0, there was no existing Registry or it
was empty.
System
Device
Listings
Checking For
Shows that detection looked for that device, followed by a
description of the device or class. If the device is
detected, Detected shows its resource information.
Network
Adapters
Listings
Checking For
This section lists the attempts to detect network
adapters.
PROTOCOL.INI If detection finds a PROTOCOL.INI file, it saves the
Section
[net_card] section in DETLOG.TXT.
NCD:
Detecting
Network
Adapter
Detection found a network adapter using safe detection
(usually PROTOCOL.INI) and the system had information
for verifying this adapter. If verified, a Detected line is
included.
NETLOG.TXT provides a similar readout to DETLOG.TXT, but focuses on
network components. It describes what network components were found on
the system, including network adapters, protocols, clients, file and print
sharing, and protocol bindings.
SETUPLOG.TXT is used to enable Safe Recovery if Windows 98 Setup fails
before the hardware detection phase begins. It allows the program to
determine exactly when the system stalled, what needs to be repeated, and
what should be skipped. This file can be found in the root directory of the boot
disk, and it contains listings in the order in which they were executed. If you
wish to use this file to manually locate a fault, examine the end of the file.
Listings include the type of installation performed, the installation directory,
any applications running during the process, errors logged during the process,
the system hardware configuration, Registry status, the files copied during
Setup, and outstanding issues that need to be completed after the next
computer restart.
NOTE
DETLOG.TXT and DETCRASH.LOG are both hidden files in the root
directory of the primary hard drive. Take care not to delete, move,
or rename them. Doing so will eliminate a proper Safe Recovery
option, thereby forcing you to repeat the entire installation
process.
As you can see, the recovery files store a wealth of valuable information you
can use in the event of a Setup failure. When confronted with an elusive
installation problem, consider opening the appropriate file in a text editor to
help pinpoint where the installation failed. You may have to remove, or
remove and replace, a problematic hardware product.
Chapter 19, "Maintaining the Modern Computer," covers techniques you can
use to troubleshoot a Windows installation when it appears the installation was
successful but the system becomes unstable soon after loading the operating
system. There are a variety of additional tools available that fall outside the
scope of this discussion.
Performing a Windows 2000 Installation
Not Quite the Same
Installing the Windows 2000 operating system on a computer is very similar to
the process for Windows 98. However, there are a few important differences.
Because Windows 2000 is not designed as a mass-market operating system, its
designers imposed much more rigid requirements on the hardware used in
conjunction with it. Although it offers much wider support than Windows NT for
multimedia devices, scanners, and other peripherals, not all such products
have Windows 2000 drivers. You cannot assume that a Windows 98 driver will
work with Windows 2000. The advantage to this more meticulous approach is
a much more reliable operating environment.
The NTFS file system is a good deal more complicated than the FAT file
systems found in Windows 98, Windows Me, and earlier Microsoft operating
systems. Employing it—which Microsoft recommends with Windows 2000—
involves different installation and management procedures.
The more robust security provided within Windows 2000 adds a few extra
steps, because user and administrative accounts must be present on the
computer for users to gain access to it. There are some other minor
differences, but anyone familiar with the Windows 98 installation process
should have no difficulty installing Windows 2000.
Preparation and Planning
Before proceeding with the actual installation, you should go through the
planning procedure outlined in Lesson 2, paying particular attention to system
requirements. Hardware compatibility is much more important with Windows
2000 than with Windows 95 or Windows 98, and you should be sure that the
system components are all included on the Windows 2000 hardware
compatibility list if at all possible. A copy of the list is included on the Windows
2000 CD (HCL.TXT, located in the Support folder). If a product isn't listed, you
can check the Microsoft Web site at http://www.microsoft.com/hcl. The final
alternative is to visit the vendor's Web site and see if a Windows 2000 driver
or support notes are available there.
It is also a good idea to check the vendor's site to see if new software or device
drivers are available for use with Windows 2000. In many cases the drivers
provided on the Windows 2000 CD will not be the most current. If new drivers
are available, you should obtain them and have them available on floppy disk
for use during installation.
Upgrades and Updates
You should make sure that the major system components—especially the
motherboard, display adapter, and hard drive or SCSI controller—have the
most recent version of available firmware. For Windows 2000 Plug-and-Play
and power management features to work properly, the system bus must
support the ACPI standard.
CAUTION
Be extremely careful when upgrading the BIOS on a component.
Be certain that the BIOS applies to the product, that it is
appropriate and approved for use with Windows 2000, and that
you carefully follow all steps in the instructions provided by the
manufacturer. Failure to do so can seriously damage the
component.
Some software products, especially those that control hardware (like scanners
or sound cards), may require updates to work properly with Windows 2000.
They also must support 32-bit drivers. Many vendors provide upgrade packs
for use with Windows 2000 to convert existing Windows 98 and Windows 95
products. Information on compatibility can be found at
http://microsoft.com/Windows/professional/deploy/compatible/.
Gathering Information
The gathering of information is very similar to that for Windows 98. In
addition, you should have available the desired name and initial password for
the administrator account that the client wants to use, and the names and
initial passwords for new user accounts that you are going to establish during
installation. For security reasons, you should recommend that your clients
change those initial passwords after installation.
Upgrade or Clean Install?
If you are installing Windows 2000 on a computer that already has an existing
installation of Windows 95, Windows 98, Windows NT Workstation 3.51, or
Windows NT Workstation 4.0, you will be offered the option during installation
of having Setup save your existing settings and applications for use with the
new operating system.
The upgrade process simplifies setup dramatically, as Windows can directly
configure a number of settings from the existing configuration. You also don't
have to worry about the boot method and how to start the Setup program.
Simply install the Windows 2000 CD in the drive and it should automatically
bring up a dialog box offering to update the current version of Windows. Click
OK to begin the installation. If the dialog box doesn't appear, click on the
drive's icon to open the dialog box. When upgrading, Windows 2000 is
installed in the same directory as your existing copy of Windows, and many of
the files already present on the drive will be overwritten with new versions.
Choosing to perform a clean install on such a system will result in Windows
2000 installing its files in a new folder. If you are installing Windows 2000 on
a computer with an unsupported previous operating system, such as a 16-bit
version of Windows or OS/2, a new copy must be installed. This means you
must set all preferences during installation, and after the process is complete,
reinstall any software that requires Windows support.
You may also choose to configure the system to dual boot and support both
operating systems, as previously discussed. This approach can be useful if
there are older programs or hardware devices that the client wishes to access
on the computer that are not supported under Windows 2000.
CD-ROM, Floppy Disk, or Network Installation?
Windows 2000 can be installed from the distribution CD-ROM, with a
combination of floppy disks and the CD-ROM, or from installation files stored
on a network drive. The simplest installation is done directly from the CDROM, but to do so the computer must be able to boot from the CD-ROM drive.
If you are running any supported version of Windows, this is the preferred
method.
If a computer does not support a bootable CD-ROM, you can create a set of
Windows 2000 boot disks or make the contents of the CD available over a
network. If you choose the network approach, the system must be bootable in
such a fashion that you can access the network with privileges to use the
directory where the files are located. Given the wide range of variables in
networks, describing all permutations is beyond the scope of this book. The
following section discusses the steps required to create the floppy disks needed
for Windows 2000 installation if you choose this method.
Creating Windows 2000 Setup Disks
If you decide to start Setup from floppy disks, you will need a set of boot disks.
Here's how to create them from the distribution CD-ROM. Have a computer
with access to a CD-ROM drive running any version of MS-DOS or Windows.
Have four blank, formatted, 3.5-inch, 1.44-MB disks and label them Windows
2000 Setup Disks 1, 2, 3, and 4. Place the Windows 2000 CD-ROM into the
CD-ROM drive. At a command prompt (either MS-DOS or Windows
COMMAND.COM), type d:\bootdisk\makeboot a: (where d: is the drive
letter of the CD-ROM drive). Insert the first floppy into the primary floppy disk
drive (A) when prompted, and follow the instructions when asked to remove
and insert the remaining three disks.
Starting Setup
There are three ways to start the Setup program. As already mentioned, you
can perform an upgrade from within a supported version of Windows. You can
boot the computer directly into the installation routine using either the
distribution CD or the startup floppies. Both of these options turn control
immediately over to the routine. The third option is to run Setup from a
command line using a variety of switches to invoke the process. As with
Windows 98, there are a variety of switches that provide access to the number
of sophisticated options that can be used to fine-tune the setup process.
There are two different command-line programs available, depending on which
operating system is used to start the computer. WINNT32.EXE is the preferred
command used for all 32-bit operating environments. WINNT.EXE is available
for use with 16-bit environments. Remember that you must have some version
of either MS-DOS or Windows available to start the computer and provide the
command prompt. This can be an operating system already installed on the
hard drive or it can be a bootable floppy. The Windows 98 Startup disk usually
has all files needed to both boot the system and provide the CD-ROM support
needed to access the Windows 2000 CD.
The following is the syntax for using WINNT32.EXE:
winnt32 [/s:sourcepath] [/tempdrive:drive_letter]
[/unattend[num]:[answer_file]] [/copydir:directory_name]
[/copysource:directory_name] [/cmd:command_line]
[/debug[level]:[filename]] [/udf:id[,UDF_file]]
[/syspart:drive_letter] [/checkupgradeonly]
[/cmdcons] [/m:directory_name] [makelocalsource]
[/noreboot]
The options are as follows:
/s:sourcepath Specifies the source location of the Windows 2000 files.
To simultaneously copy files from multiple servers, specify multiple /s
sources. If you use multiple /s switches, the first specified server must be
available or Setup will fail.
/tempdrive:drive_letter Setup places its temporary files on the
specified partition and installs Windows 2000 on that partition.
/unattend Updates the previous version of Windows 2000, Windows NT
4.0, Windows NT 3.51, Windows 95, or Windows 98 automatically. All
user settings are taken from the previous installation. Use of this switch
affirms reading and accepting the Microsoft License Agreement for
Windows 2000.
NOTE
As a technician you must understand that by using this switch
to install Windows 2000 on behalf of a third party, you are
confirming that the end user (whether an individual or a
single entity) has received, read, and agreed to all of the
terms contained in the Windows 2000 Microsoft License
Agreement. OEMs may not specify this key on machines being
sold to final end users.
/unattend[num]:[answer_file] Performs a fresh installation in
unattended Setup mode on computers running Windows NT or Windows
2000. The declared answer file provides Setup with any custom
specifications. Num denotes the number of seconds delayed between the
time that Setup finishes copying the files and the time it restarts the
computer. Answer_file is the name of the specified answer file.
/cmd:command_line Setup carries out the command_line program
before the final phase of Setup. This happens after the computer has
restarted twice and after Setup has collected all the configuration
information, but before Setup is completed.
/debug[level]:[filename] Creates a debug log at the level specified.
The log levels are: 0 = severe errors, 1 = errors, 2 = warnings, 3 =
information, and 4 = detailed information for debugging. Each level
includes the levels below it.
/udf:id[,UDF_file] Indicates an identifier (id) that Setup uses to specify
how a Uniqueness Database File (UDF) modifies an answer file (see
/unattend). UDF settings override values in the answer file, and the
identifier determines which values in the UDF are used.
/syspart:drive_letter Setup copies the startup files to a hard disk and
marks the disk as active. You can then install them into another
computer, and it will automatically start the machine at the next Setup
phase. The /tempdrive parameter must be used in conjunction with the
/syspart parameter.
/checkupgradeonly Checks the computer for Windows 2000 upgrade
compatibility. When used with Windows 95 or Windows 98 upgrades,
Setup creates a report named UPGRADE.TXT in the Windows Installation
folder. For Windows NT 3.51 or 4.0 upgrades, the report is WINNT32.LOG
in the Installation folder. The report includes information on MS-DOS
configuration (including information on the contents in any existing
AUTOEXEC.BAT and CONFIG.SYS file that might create problems),
unsupported Plug-and-Play hardware, incompatible software products that
may require upgrade packs, and software that may have to be reinstalled
to work properly. The report also provides valuable links to the Microsoft
Web site as appropriate. Before exiting, you are offered the options of
saving or printing the report.
NOTE
This is a very useful switch that can be used anytime there is a
question concerning the compatibility of any component hardware
or software when performing an upgrade. Not only does it provide
an exhaustive check of the system, but you can use the resulting
report to explain needed system upgrades to the client.
/m:directory_name Setup copies replacement files from an alternate
location, if those files are present there, instead of using the files located
in the default location.
/makelocalsource Setup copies all installation source files to the local
hard disk. This is used when the CD will not be available later in the
installation.
/noreboot Setup won't automatically restart the computer after the file
copy phase of Winnt32.
The following is the syntax for using WINNT.EXE:
winnt [/s:sourcepath] [/t:tempdrive] /u:answer file][/udf:id [,UDF_file]
The options are as follows:
/s:sourcepath Sets the source location of the Windows 2000 files. It
must show the full path, such as x:\[path] or \\server\drive[\path].
/t:tempdrive Places temporary files on the specified drive and installs
Windows 2000 on that drive.
/u:answer file Used in conjunction with the /s switch, this option
performs an unattended setup using an answer file to complete some or
all of the prompts normally activated during Setup.
/udf:id [,UDF_file] Indicates an identifier (id) used with a UDF to
modify an answer file (see /u entry). Use /udf parameters to override
values in the answer file.
/r:folder Specifies an optional folder to be installed. The folder remains
after Setup finishes.
/rx:folder Specifies an optional folder to be copied. The folder is deleted
after Setup finishes.
/e:command Specifies a command to be executed at the end of
graphical user interface (GUI) mode Setup.
/a Enables accessibility options.
The Step-by-Step Installation Process
No matter which method you use to start the process, the main steps are
similar. As with Windows 98, the majority of the steps are performed
automatically and are actually transparent to the user. In a clean install from
either the CD or the startup disks, the user is first presented with a series of
blue screens. For an upgrade, the entire process uses familiar Windows dialog
boxes. So long as you undertake proper advanced planning, and the computer
where you are loading Windows 2000 has compatible hardware, the actual
creation of the new filing system should be simple and straightforward.
Choosing a File System and Disk Partition
Because Windows 2000 supports a variety of file systems, it will prompt you to
specify which you wish to use. If the system will be used only for Windows
2000 operations, Microsoft recommends using NTFS5 for all drives and
partitions. This is the only file system that offers full support for all of Windows
2000's features and provides access to all of the security functions. You can
upgrade existing FAT and NTFS partitions during the setup process, or later
after the new system is up and running.
Keep in mind that you only need to actually create or size the partition that
will hold Windows 2000. If you are planning a dual boot system, a total NTFS
may not be the best approach. The computer must have a FAT file system on
the primary partition for MS-DOS, Windows 95, and Windows 98 access. If you
have any existing DriveSpace or DoubleSpace volumes on the system, they
must be converted prior to starting an upgrade to Windows 2000. Accessing
the new file system using a dual boot system with Windows NT 4.0 requires
that the Windows NT system have Service Pack 5 installed.
No matter which file system you choose, it is important make sure there is
enough hard disk space available beyond the minimum installation
requirements to leave room for system upgrades, utilities, a virtual memory
paging file, and any applications planned for that drive.
Disk Validation and File Copy
Once file system options have been determined, Setup performs an
examination of the hard disk partitions, making sure that they are ready to
receive the operating system. If that process completes successfully, the
appropriate folders are created and the operating system files are
uncompressed and copied to the target hard drive. At this point, the computer
automatically reboots.
Primary Device Detection and Information Gathering
From this point on, the setup process continues using the familiar Windows
interface. There may be a delay of several minutes while Setup conducts an
inspection of the target computer and installs and activates devices like the
keyboard and mouse.
Several dialog boxes are then presented to the user to verify the installation
key, customize regional settings, collect the user's name and company name,
set the computer name and administrative password, collect the date and time
settings from the system clock, and obtain information about any existing
network, workgroup, and domain environments the new system will be joining.
CAUTION
Be sure to write down both the administrative user account and
password immediately. Without the proper information, you will be
denied access to the system and will be unable to complete the
installation process.
Operating System Installation
Once all that information is gathered, Setup presents a dialog box offering
optional components like IIS (Internet Information Services) and advanced
management and monitoring tools. Clicking OK causes the Windows 2000
installer to actually install those operating system components. This step also
includes setting up the Start menu configuration, setting Registry entries for
the selected components, saving system settings, and removing the temporary
files used during the setup process. Once these tasks are complete, Setup
restarts the system.
Postinstallation Tasks
Setting Up Local User Accounts
The official installation process is now finished, but you must perform some
additional tasks before the job is actually complete. When the system restarts,
a dialog box appears, allowing access to the system. You must press
Ctrl+Alt+Delete to proceed to the user logon screen. This step is a security
method to prevent a program from running in the background that can capture
logon information.
Pressing the key combination produces a logon screen that asks you for a user
name and password. Entering a new name and password creates a basic user
account that will provide simple access to this computer. For full rights you
must log on using an account that has administrative privileges. At this point
the only such account is the one you created during the setup process.
Joining Networks and Domains
Both the administrative account and the new user account are specific to this
computer, and they do not grant access to any network or domain that you
have specified during installation. To gain full access to the network you must
now join the computer to any desired workgroup or domain and set up the
appropriate domain or workgroup user accounts needed to access them. That
may require administrative access to the servers for those networks.
Creating an Emergency Repair Disk
The final task is to create an emergency repair disk (ERD). This disk contains
three files needed to restore the original registry created during the setup
process. This is a change from Windows NT 4.0, which actually saved a copy of
the registry on the ERD.
The Windows 2000 ERD contains the AUTOEXEC.NT, CONFIG.NT, and
SETUP.LOG files. AUTOEXEC.NT and CONFIG.NT are used to initialize the MSDOS environment, and SETUP.LOG lists the files installed by Setup, as well as
their CRC (cyclical redundancy check) data for use during the repair process.
The ERD is not a bootable disk, and by itself cannot repair anything. It is the
last line of defense if the system becomes corrupted, and the Registry must be
restored. The details of this process are covered in more detail in Chapter 19,
"Maintaining the Modern Computer."
To create an ERD, click the Start menu and choose
Programs/Accessories/System Tools/Backup. Insert an empty, high-density,
3.5-inch floppy disk into the floppy drive. Click the Welcome tab from the open
application and follow the prompts to create the ERD disk. When the process is
complete, remove the disk, label it with both the date and the computer name,
and then store it in a safe place.
Troubleshooting
Given the rigid hardware compatibility requirements and the thorough nature
of the Setup routine, the majority of Windows 2000 installations should
perform as the manufacturer intended—without problems. The following
sections provide suggested troubleshooting tips in case the process fails.
Check Hardware and Software
Run a second compatibility check on all components involved in the
installation. Make sure that all hardware is actually listed in the hardware
compatibility list, and replace any items that are not. If this is an upgrade,
make sure that any software already on the system is Windows 2000compliant. Try running the Setup program with the /u switch and check the
compatibility report for any problems. Resolve any reported issues. Inspect the
distribution CD-ROMs for any flaws.
Repeat the Installation
Once you have finished the compliance check, repeat the installation routine.
If it fails a second time, you must take further steps to identify and resolve the
issue.
Inspect the Logs
Windows 2000 creates several logs during the installation process that can be
accessed with a text editor. They are usually located in the \Winnt directory.
They include the following:
Setupact contains an action log describing every step that Setup performs
in chronological order. It also includes the errors that are written into the
error log. A quick scan of this file can often pinpoint a device driver that
did not load or a file that was not copied.
Setupapi is a log of the installation of the different device classes on the
computer.
The Events Log can be accessed if the installation completes but you are
still having trouble with a service that fails to start. This utility can be
accessed from the Control Panel under Administrative Tools. It is covered
in more detail in Chapter 19, "Maintaining the Modern Computer."
Simplify the Hardware Configuration
If you cannot pinpoint the exact problem and suspect it is hardware-related,
you can remove components that are not critical to system operation (like a
sound card or video capture device) and run the installation program again.
Once you have successfully installed Windows 2000, you can add these
components individually.
Use the Recovery Console
Windows 2000 provides a recovery console that can provide basic repairs to a
corrupted system, as well as offering command-line access to a variety of
utilities for inspecting and repairing components. This program is covered in
detail in Chapter 19, "Maintaining the Modern Computer."
Lesson Summary
The following points summarize the main elements of this lesson:
Most of the Windows installation process is automated.
Although similar in appearance, there are fundamental differences
between the Windows 98 and Windows 2000 installations.
If proper planning has been performed, all system requirements met, and
proper settings selected, the majority of installations will proceed without
problems.
Although the automated installation routine provided with Windows will
satisfy the requirements for most configurations, using the command-line
options provides much more control for the experienced user.
In case of difficulty, both versions of Windows offer a variety of tools to
assist in troubleshooting.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
The Windows Family
The Windows family of operating systems includes a variety of products
tailored to the needs of different users and environments.
Windows 98 and Windows Me are designed for the typical end user. Both
offer the broadest range of hardware and software support.
Windows 2000 is the most robust version of Windows. It offers the most
reliability and security of any member of the Windows family.
The Windows family includes several products designed specifically for
network applications ranging from LANs to complex enterprise data
centers.
Preparing for Windows Installation
Proper planning and system preparation are critical for a trouble-free,
optimal Windows installation.
It is possible to operate more than one operating system on the same
computer, but additional care in designing the file system must be taken.
Windows 2000 requires much more critical evaluation of both the
hardware and software components to ensure smooth installation and
subsequent operation.
Prior to beginning the actual installation, make sure that primary
hardware components are equipped with a supported BIOS.
Although the varieties of Windows may all look similar to the end user,
each has its own unique hardware requirements.
Installing Windows
Superficially, the installation process appears the same for both Windows
98 and Windows 2000. In reality, they are quite different.
During Setup, the installer must have ready information concerning
system configuration and software drivers. You must be ready to answer
all prompts needed to configure the system.
With the maturation of Plug-and-Play technology, most Windows
installations proceed without difficulty.
In the event that an installation does encounter problems, the Windows
environment provides a number of tools for troubleshooting and
producing a successful outcome.
The installation process installs the operating system, but additional tasks
are often required after the process is completed to set the system up on
networks, customize settings, and ensure that third-party applications run
successfully.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. List several differences between Windows 98 and Windows 2000.
2. Explain some of the primary considerations in designing a dual boot
system.
3. Where can you find information about what hardware can be used with
Windows 2000?
4. What is the purpose of the Windows 98 startup disk?
5. What is an ERD?
6. What steps have to be taken to use a compressed drive created under
Windows 95 or Windows 98 with Windows 2000?
7. What is Safe Recovery?
8. What is Fdisk?
9. What are the four setup options offered after Windows 98 Setup prepares
the installation directory?
10. Can Setup be run for both Windows 98 and Windows 2000 from MS-DOS?
11. What is the purpose of the Check Upgrade Only function during Windows
2000 installation and how is it invoked?
12. What should be the first step in troubleshooting any failed Windows
installation?
13. What is the first step required to log on to a Windows 2000 machine (not
during installation, but at any time the system is accessed after Setup is
complete)? What is the purpose of this step?
14. What are the basic minimum system requirements required to run
Windows 2000?
Answers
3 4
Chapter 18
Running Microsoft Windows
About This Chapter
This chapter focuses on operating and managing Microsoft Windows 98 and
Microsoft Windows 2000 with emphasis on the skills needed for the A+
Certification Exam. To gain the high level of proficiency required of today's
computer professional, you should go on to obtain advanced training in these
operating systems and build a library of references after completing this
chapter.
NOTE
This chapter focuses on the Windows 98 and Windows 2000
operating systems because they are the primary focus on the A+
Exam.
Before You Begin
This chapter assumes you are familiar with basic use of the Windows operating
environment and the material presented in Chapter 17, "Introducing and
Installing Microsoft Windows." To get the full benefit of the discussion, work
along with the text at a computer with the operating system installed. You
should already be comfortable with the Windows user interface, operating in
DOS mode, and PC system components. You should also work through the
lessons in this chapter in order, as each one builds on the preceding material.
3 4
Lesson 1: How Windows 98 Works
This lesson explains the basic design of the Windows 98 system architecture,
how the operating system manages tasks, and the entire system boot process.
You should be familiar with the material in this lesson before moving on to
Lessons 2 and 3 in this chapter. If possible, you should follow this lesson by
performing the actual steps involved in examining the files mentioned on your
computer. The same is true for the material presented in Lessons 2 and 3, as
well as the material in Chapter 19, "Maintaining the Modern Computer."
After this lesson, you will be able to
Understand the Windows 98 system architecture
Understand how Windows 98 handles tasks and allocates memory
Identify the elements of the boot process and core files of Windows 98
Estimated lesson time: 55 minutes
The Windows 98 System Architecture
Basic Functions and Features
Windows 98, like its predecessor Microsoft Windows 95 and the newer
Microsoft Windows Me, is a natural successor to the MS-DOS and Microsoft
Windows 3.1 environments. It is a true 32-bit operating environment offering
improved performance, preemptive multi-tasking and multi-threading
operation, advanced hardware support, better operating system stability, and
the ability to manage large amounts of memory.
Like Windows 2000, Windows 98 employs dynamic hardware and system
environment configuration technology, which makes it easier to install devices
or reconfigure the system. This includes support for the Windows Driver Model,
allowing both operating systems to share a common driver library.
The operating system can be broadly broken down into two major components:
the core and ancillary systems. The Windows 98 core consists of four
components: the Graphical Device Interface (GDI), the kernel, the user
component, and the user interface. These four elements all have a matching
pair of two 32-bit and one 16-bit dynamic-link libraries (DLLs). This allows
Windows 98 to use the 32-bit mode of operation to improve performance, also
allowing backward 16-bit compatibility for old devices and applications.
All of the ancillary systems operate using 32-bit mode. Windows 98 comes
with a collection of 32-bit file system drivers that support FAT16, FAT32, and
ISO 9660 format CD-ROM (compact disc read-only memory) discs, and the
DVD (digital video disc) Universal Disc Format. The following sections provide a
closer look at the four primary components and some key subsystems.
Graphical Device Interface
The GDI is an imaging system that draws all the objects displayed on the
screen or reads the information to devices like printers that can receive
graphical output. The GDI is also the component responsible for interacting
with the display system and its related drivers. The average user often takes
the generation of the user interface for granted; in reality, it is one of the
most complex tasks performed by the operating system. Many of the memory
problems associated with earlier versions of Windows could be traced back to
graphics display problems and GDI management.
User Interface
The Windows 98 user interface is a 32-bit shell that includes a variety of tools
to make use of the file system and gain access to system services. These
include My Computer, the Network Neighborhood, and Windows Explorer. All
Windows applications can make use of the shell services, including dialog
boxes and the ability to list and view files.
User Component
This core element of the operating system is the I/O (input/output) manager.
It receives and routes input from the mouse, keyboard, microphone, and other
input devices. It also routes traffic to and from the communications ports, the
system timer, and the sound card. In addition, it acts as the output coordinator
for the GDI by controlling the output of display elements like menus, dialog
boxes, and icons.
Kernel
The kernel can be thought of as the core of the core of the operating system.
It controls all tasks: When an application opens, it is the kernel that invokes
the executable file and terminates it when it is done. It loads and manages all
DLLs and allocates memory. The kernel is also responsible for all preemptive
multi-tasking and multi-threading operations.
Process Scheduler
The Process Scheduler is responsible for providing system resources. Through
proper allocation, it allows multiple applications to run simultaneously.
Windows 98 advances the cooperative multi-tasking found in Windows 3.1,
which required an application to periodically relinquish access to system
services to allow another application to execute. A more elegant approach is
preemptive multi-tasking, which Windows 98 uses for all 32-bit applications.
The Process Scheduler executes this by dividing the amount of time each
application can have to access to the CPU (central processing unit) and other
system resources. These time slices are called threads, so the term multithreaded can be applied to Windows 98, meaning that an application can have
more than one thread open at a time. As a result, Windows 98 is known as a
multi-threading, multi-tasking operating system.
File System Drivers
Like Windows 2000, Windows 98 offers support for the Windows Driver Model
(WDM), allowing compatible devices to use the same driver for both operating
systems. Its Plug-and-Play feature is much improved over Windows 95,
allowing for dynamic hardware configuration and all but eliminating the need
for jumpers and manual configuration of adapter cards.
The Virtual Machine Manager
The Virtual Machine Manager (VMM) oversees the key resources required by
both applications and system processes. These include process scheduling,
memory management, exception handling (issuing General Protection Faults
or GPFs), and mapping access to the system BIOS (basic input/output system),
device drivers, and TSR (terminate-and-stay-resident) programs.
The VMM manages the system's virtual machine, the environment in which all
system processes operate. All 32-bit applications are provided their own
individual virtual machines, as are any MS-DOS programs that run in a
protected space. Legacy 16-bit Windows applications are all grouped together
in a single 16-bit virtual machine that emulates an 8086 processor. This 16-bit
machine is said to be operating in V86 mode.
The Windows 98 Virtual Memory Model
Using virtual memory, Windows 98 can provide more functional memory to
applications than the amount of RAM (random access memory) actually
present on the computer. When an application or process needs more memory
than is actually available, the operating system moves data between virtual
memory and the system's hard disks to free RAM for the active process.
With MS-DOS and versions of Microsoft Windows prior to Windows 95, all
processes and active applications shared a single address space. Without the
use of special memory managers, all applications and most system code had to
reside in the first 640 KB of physical memory (RAM). If any process corrupted
the memory stack, the entire system would fail. This memory model
significantly limited how much memory was actually available to both the
operating system and any application and compromised the integrity of the
operating environment.
Windows 98 provides a unique virtual address space for each process or
program, using a demand-page virtual memory system that can be as large as
4 GB. Part of the space is reserved for system processes and part is available
for use by applications. A process can only access memory that has been
specifically allocated for its use. The Windows 98 core components (such as the
kernel and the GDI) and shared DLLs are contained in a shared address space.
The 4 GB is allocated and used as follows:
0–640 KB. The first 640 KB is reserved for real-mode device drivers and
TSRs. This allows backward compatibility for older applications, which
expect to see RAM in this location.
4 MB–2 GB. This region is the province of Win32-based applications.
Each program is in its own private address space.
2 GB–3 GB. This 1-GB space contains the shared Windows 98 core
components and DLLs. This region can be read by any application or
process that needs these resources.
3 GB–4 GB. This is the privileged-mode space, holding the system kernel
code, which controls and directs access to all hardware and memory
addresses.
The Virtual Memory Swap File System
Obviously, if Windows 98 has the ability to move data between physical
memory and virtual memory, there has to be a specially designated file (and
file structure) on the hard disk to be used as a "scratch" area. It is known as
the swap file. When physical memory becomes low, Windows 98 automatically
adjusts the size of the swap file and the way virtual memory is allocated. This
is a major improvement over Windows 95, which required the user to set the
amount of space used by the swap file and designate if it would operate in 32bit mode. In Windows 98, all this is usually done automatically in 32-bit mode.
The user can still override the settings, but this is rarely necessary.
The Memory Pager
The Memory Pager actually handles moving blocks of data to and from virtual
memory into the physical address space by dividing the data in equal blocks
known as pages. The code contained in specific pages is moved into RAM when
needed. This approach allows any given application access to the full 2 GB of
memory space provided for it in the Windows 98 memory model.
DOS Mode Support
DOS mode support allows a legacy application to gain exclusive access to the
system resources it needs to operate. Windows 98 does this by creating an
exclusive operating environment known as MS-DOS mode. Applications
running in this space have access to the resources they need as long as their
process is running. This is an exception to the multi-tasking feature mentioned
earlier. Windows 98 provides for this by the use of separate virtual machines
for each MS-DOS mode session.
The WDM
The WDM is the device driver architecture that first appeared in Windows 95
OSR2 and has been improved to work with both Windows 98 and Windows
2000. Some drivers originally designed for use with Windows 95 using the
WDM may not be compatible with these newer operating systems. This
architecture was designed to create a single driver that can be used across the
range of Windows operating systems. This offers several benefits: It reduces
the cost of providing device drivers, makes devices available on a wider range
of platforms, and simplifies distribution.
The WDM architecture is arranged in a series of layers, with a hardware device
at the bottom and the applications using it at the top. Figure 18.1 depicts the
layout of the architecture, and the following list describes each element's
function within it.
Figure 18.1 The Windows Device Model architecture
An individual WDM driver belongs to one of several classes:
Device class drivers contain class-specific functions. They are not specific
to a given piece of hardware or system bus, but provide a more generic
function. These are used for classes of products like mice, joysticks, and
keyboards.
Bus class drivers are available for both USB (universal serial bus) and
IEEE 1394 buses on a system. They work to speed up communications
between the hardware layer and the minidrivers.
Minidrivers are hardware-specific and generally operate a class of devices
operating on a specific type of bus. This class includes support for SCSI
(Small Computer System Interface), USB, DVD, IEEE 1394, and network
adapters. Minidrivers can be written to support multifunction cards like a
video capture card that includes both video and sound functions on a
single product. Windows 98 dynamically loads and unloads minidrivers as
they are needed or released to save on memory and avoid usage
conflicts.
Virtual device drivers (VxDs) are 32-bit protected mode drivers
responsible for managing a system resource (either hardware or
software). These drivers do not directly control the hardware device, but
act as an interpreter between the hardware and the application, ensuring
that only one system process controls the resource at any specific time.
Like minidrivers, VxDs are only held in memory when they are actually in
use. Some VxDs are also used with legacy hardware and software to allow
them to function within the Windows 98 environment.
NTKERN.VXD is the operating system services layer for Windows 98. This
layer is always system-specific and allows the minidrivers to function with
more than one operating system. Under Microsoft Windows NT, the
operating system services layer is the hardware abstraction layer (HAL).
32-Bit VFAT
Disk access is provided through the 32-bit VFAT (Virtual File Allocation Table).
Unlike the 16-bit file allocation table (FAT) used before Windows 95, VFAT is a
virtual device driver that operates in protected mode. This provides more
reliability and works with a greater variety of hardware. Don't confuse 32-bit
VFAT with 32-bit FAT, which has to do with how data is stored on a hard disk
partition (the cluster size). VFAT has to do with how files are accessed.
Like the older 16-bit FAT, VFAT links clusters of files together. In the old 16bit system, the largest number of clusters on a drive was 65,525; with 32-bit
operation the maximum cluster size is now 268,435,445.
The first 8 bytes of the FAT32 table are reserved for system use. The value of
the final byte is normally 0, set to that value during system startup. When you
issue a proper shutdown command on the system, the value is changed to 1.
If, during startup, Windows detects that the value of the eighth byte is 0, it
assumes the system shut down improperly and ScanDisk runs during the boot
process.
NOTE
VFAT was formerly known as 32-bit file access in Windows 3.1.
Don't confuse 32-bit file access with a 32-bit operating
environment; they are not the same.
Long Filename Support
In MS-DOS and Windows 3.x, filenames were limited to an 8.3 format; that is,
the filename itself was restricted to a maximum of eight characters in length,
and the extension to a maximum of three characters in length. Filename and
extension are connected by a period, or dot. Beginning with Windows 95, the
operating system added long filenames (LFNs) support. The LFN removes the
8.3-filename limitations of older MS-DOS and Windows operating systems. In a
regular MS-DOS 8.3 file specification directory, all file records are stored in
32-byte records. Of the 32 bytes, 10 are reserved. The other 22 bytes are
used to store information on starting clusters, creation date, and creation
time, and 11 bytes are for the filename itself. LFNs exist on FAT partitions by
chopping the filename into 12-byte chunks (stealing one of the reserved
bytes) and allowing up to 13 chunks, creating a filename of up to 255
characters.
When an LFN is saved, the system creates a short name that conforms to the
8.3 standard. Then, each group of 12 characters is cut off and stored in its own
directory section. The directory entries that make up the LFN are called LFN
entries. These must be backward compatible with MS-DOS programs and with
MS-DOS itself.
NOTE
To make files backward compatible with MS-DOS, Windows takes
the first six characters (no spaces) of the filename, adds a tilde
(~), a number, and then the extension. If two or more files have
the same first six characters, the number is incremented by one
for each. For example, two files named LONG FILE NAME ONE.TXT
and LONG FILE NAME TWO.TXT would become LONGFI~1.TXT and
LONGFI~2.TXT.
To make LFNs compatible with MS-DOS means to make sure that MS-DOS
ignores the LFN entries in the directory structure. This is achieved by giving
LFN entries the bizarre attribute combination of hidden, read-only, system,
and volume label. There is nothing in the MS-DOS code that tells it what to do
if it encounters a file with this combination of attributes, so MS-DOS does not
interfere with it.
CAUTION
Older disk utilities are incompatible with LFNs and will try to erase
the LFN entries. It is critical that any disk utility that tries to
diagnose the directory structure, including the Scandisk utility that
is included with MS-DOS 6 and earlier, should never be run on a
computer with LFNs. The Scandisk versions that come with
Windows 98 and Windows Me are compatible with LFNs.
The Windows 98 Boot Process
Understanding the boot sequence for the operating systems you encounter
during your work is a necessary skill. The rest of this lesson is devoted to the
sequence of steps that begins when power is supplied to the computer or the
RESTART command is issued and ends when control of the system is returned
to the user interface. This process can be broken down into three broad
phases.
The BIOS Initialization Phase
During the BIOS initialization phase, the computer's BIOS and the embedded
power-on self test (POST) code hold system control. Just how this phase
affects Windows depends on the type of BIOS the system has. Older machines
that do not support Plug-and-Play enable devices in a static mode based on the
device settings. Computers with a Plug-and-Play-enabled BIOS initializes and
completes the configuration of the Plug-and-Play-capable devices before the
POST begins, resolving possible conflicts. It then looks for the existence of an
operating system. At this point, Windows 98 begins taking control of the
operating environment.
Hardware Profile and Real-Mode Driver Loading Phase
The initial phases of Windows 98's startup are actually conducted in real mode.
In the real mode environment, Windows 98 operates much like MS-DOS. The
Windows 98 IO.SYS is the first system file loaded into memory. It actually
incorporates many of the features of the old MS-DOS IO.SYS, as well as much
of the functionality of the MS-DOS MSDOS.SYS file. As the following table
indicates, it loads many of the core settings that once were the province of
CONFIG.SYS.
Entry
Function
dos=high
Specifies that MS-DOS is to load in the high
memory area (HMA). Also, the upper memory
block (UMB) value is included if EMM386 is loaded
from CONFIG.SYS. (IO.SYS does not load
EMM386.)
HIMEM.SYS
Enables access to the HMA and loads and runs the
real-mode memory manager. HIMEM.SYS is
loaded by default in Windows 98.
IFSHLP.SYS
The 32-bit Installable File System Manager uses
the services provided by this driver to assist in
trapping real-mode file system and networkrelated application programming interfaces (APIs).
SETVER.EXE
Optional TSR-type device included for
compatibility. Some MS-DOS-based applications
require a specific version of MS-DOS to be
running. This file responds to applications that
query for the version number and sets the version
number required.
files=
Specifies the number of file handle buffers to
create. This is specifically for files opened using
MS-DOS calls and is not required by Windows 98.
It is included for compatibility with older
applications. The default value is 60.
lastdrive=
Specifies the last drive letter available for
assignment. This is not required for Windows 98
but is included for compatibility with older
applications. If Windows 98 Setup finds this entry,
it is moved to the registry. The default value is z.
buffers=
Specifies the number of file buffers to create. This
is specifically for applications using IO.SYS calls
and is not required by Windows 98. The default
value is 30.
stacks=
Specifies the number and size of stack frames.
This is not required for Windows 98 but is
included for compatibility with older applications.
The default value is 9256.
Indicates what command process to use. By
default, the /p switch is included to indicate that
the command process is permanent and should
shell=COMMAND.COM not be unloaded. If the /p switch is not specified,
AUTOEXEC.BAT is not processed and the
command process can be unloaded when quitting
the operating system.
fcbs=
Specifies the number of file control blocks that
can be open at the same time. You should use this
line in CONFIG.SYS only if you have an older
program that requires such a setting. The default
value is 4.
During this phase, Windows 98 determines the computer's configuration. It
performs a detection sequence that examines IRQs (interrupt requests), the
system BIOS, Plug-and-Play data, and whether the device is actually a laptop
docking station. At that point, it loads the MSDOS.SYS settings and processes
the CONFIG.SYS and AUTOEXEC.BAT files, if they exist.
Be aware that several files are automatically loaded by IO.SYS in addition to
any invoked by any user-defined startup settings: HIMEM.SYS, IFSHLP.SYS,
SETVER.EXE, and DBLSPACE.BIN or DRVSPACE.BIN (if DLBSPACE.INI or
DRVSPACE.INI exists in the root of the boot drive). You cannot edit or directly
adjust IO.SYS without causing it to fail. If you do not wish to load any of these
files, they should be renamed.
Using MSDOS.SYS for Custom Configurations
There is still an MSDOS.SYS file employed in Windows 95 and Windows 98, but
it is not the same as in MS-DOS. It actually replaces the functions of
CONFIG.SYS. This is the proper place to make custom boot configuration
settings unless there is some overriding reason to use CONFIG.SYS and
AUTOEXEC.BAT for backward compatibility. They are not actually necessary
unless you need to load them to support older MS-DOS applications or
hardware.
NOTE
If you invoke any primary real-mode drivers using the
CONFIG.SYS and AUTOEXEC.BAT files, you may force Windows 98
into real-mode operation for all or part of its functions. This can
significantly degrade system performance.
The following example shows a very simple MSDOS.SYS file.
;FORMAT
[Paths]
WinDir=C:\WINDOWS
WinBootDir=C:\WINDOWS
HostWinBootDrv=C
[Options]
BootMulti=1
BootGUI=1
DoubleBuffer=1
AutoScan=1
WinVer=4.10.1998
;
;The following lines are required for compatibility with other programs.
;Do not remove them (MSDOS.SYS needs to be >1024 bytes).
;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxa
;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxb
In Windows 98, you can use a text editor to adjust the settings in MSDOS.SYS
just as you could with CONFIG.SYS under DOS. The following table provides a
list of entries and their function. You may wish to examine the contents of this
file on your system (assuming you are using Windows 98). To do so, you will
need to enable viewing hidden files, as MSDOS.SYS is a hidden system file. If
the value setting uses a Boolean operator, set it to 1 to enable the option and
0 to turn it off.
CAUTION
Be sure not to change any values you don't completely understand
because they will alter the method and ability of the system to
start. Normally, when modifying this file you should save the
original version under another name so that it can be easily
restored if undesirable results are obtained.
Entry
Description
[Paths] Section
HostWinBootDrv=c
Defines the location of the boot drive root directory.
WinBootDir=
Defines the location of the necessary startup files.
The default is the directory specified during Setup;
for example, C:\Windows.
WinDir=
Defines the location of the Windows 98 directory as
specified during Setup.
[Options] Section
AutoScan=
Enables ScanDisk to run automatically when your
computer restarts. The default is 1. When this value
is set to 1, ScanDisk prompts you to indicate if you
want to run ScanDisk; if you do not respond after 1
minute, ScanDisk runs automatically. Setting this
value to 0 disables this feature. Setting it to 2
launches ScanDisk automatically (if needed)
without prompting you.
BootDelay=n
Sets the initial startup delay to n seconds. The
default is 2. BootKeys=0 disables the delay. The
only purpose of the delay is to give the user
sufficient time to press F8 after the Starting
Windows message appears.
BootFailSafe=
Enables safe mode for system startup. The default
is 0. (This setting is typically enabled by equipment
manufacturers for installation.)
BootGUI=
Enables automatic graphical startup into Windows
98. This is equivalent to putting the win statement
in AUTOEXEC.BAT. The default is 1.
Enables the startup option keys (that is, F5, F6, and
BootKeys=
BootMenu=
F8). The default is 1. Setting this value to 0
overrides the value of BootDelay=n and prevents
any startup keys from functioning. This setting
allows system administrators to configure more
secure systems.
Enables automatic display of the Windows 98
Startup menu, so that the user must press Ctrl to
see the menu. The default is 0. Setting this value to
1 eliminates the need to press Ctrl to see the menu.
Sets the default menu item on the Windows Startup
menu; the default is 3 for a computer with no
BootMenuDefault=#
networking components and 4 for a networked
computer.
BootMenuDelay=#
Sets the number of seconds to display the Windows
Startup menu before running the default menu
item. The default is 30.
BootMulti=
Enables dual-boot capabilities. The default is 0.
Setting this value to 1 enables you to start MS-DOS
by pressing F4 or by pressing F8 to use the
Windows Startup menu.
BootWarn=
Enables the safe mode startup warning. The default
is 1.
BootWin=
Enables Windows 98 as the default operating
system. Setting this value to 0 disables Windows 98
as the default; this is useful only with MS-DOS
version 5 or 6.x on the computer. The default is 1.
DblSpace=
Enables automatic loading of DBLSPACE.BIN. The
default is 1.
DoubleBuffer=
Enables loading of a double-buffering driver for a
SCSI controller. The default is 0. Setting this value
to 1 enables double buffering if required by the
SCSI controller.
DrvSpace=
Enables automatic loading of DRVSPACE.BIN. The
default is 1.
Enables loading of COMMAND.COM or
DRVSPACE.BIN at the top of 640 K memory. The
LoadTop=
Logo=
Network=
default is 1. Set this value to 0 with Novell NetWare
or any software that makes assumptions about what
is used in specific memory areas.
Enables display of the animated logo. The default is
1. Setting this value to 0 avoids a variety of
interrupts that can create incompatibilities with
certain third-party memory managers.
Safe mode with networking is not supported in
Windows 98. This value should be set to 0 or left
blank to disable this feature.
Loading CONFIG.SYS and AUTOEXEC.BAT
As mentioned previously, although not recommended, you can use both
CONFIG.SYS and AUTOEXEC.BAT to modify how Windows 98 operates. In
general, they work just as they did under MS-DOS, but there are some
important things to consider and be aware of when using these files:
Don't include any mouse support in either file. Windows 98 includes
internal support for most mice.
Windows 98 has its own disk caching and double-buffering algorithms, so
you do not need to include the SMARTDRV.SYS command in CONFIG.SYS.
The comspec, path, prompt, net start, and temp settings made via
AUTOEXEC.BAT under MS-DOS are now automatically handled by IO.SYS
in Windows 98. They can be overridden by AUTOEXEC.BAT without
affecting the 32-bit mode operations of Windows 98.
Do not reference other versions of Windows that might still be on the
drive under Windows 98 in the AUTOEXEC.BAT file.
Be sure the Windows and Windows\Command directories are in any new
path statements.
Device and memory settings should be handled via the System or Device
Manager or Registry in Windows 98 whenever possible, avoiding the
CONFIG.SYS and AUTOEXEC.BAT files.
Protected Mode Initialization Phase
Once the real mode components are in place, the startup invokes WIN.COM.
This file manages the initial system inspection for 32-bit operation and loads
the core Windows operating system components.
The boot process loads a series of static and dynamic VxDs, including
VMM32.VXD. This file is a composite VxD that contains the VMM and the real
mode loader. It also invokes any other VxDs that reside in the
Windows\System\Vmm32 directory. The exact list of VxDs loaded at this point
varies based on the machine configuration. It is possible to see which ones are
called by examining the [386enh] section of the WINDOWS.INI file.
Once the virtual machine is running, the SYSTEM.INI file is processed, and the
system is fined tuned with those settings. Next, the configuration manager is
started, employing information from the Plug-and-Play BIOS, or if the system
does not have one, by developing its own device list and loading the
appropriate drivers. The configuration manager resolves any conflicts and then
initializes the drivers. If a conflict cannot be resolved, one or more of the
devices may be disabled.
With the hardware structure defined and appropriate VxDs in place, the final
system components can be loaded. These include: KERNEL32.DLL (which
provides the main Windows 98 components), KRNL386.EXE (which loads
device drivers), GDI.EXE and GDI32.EXE (which manage and provide the GUI),
and USER.EXE and USER32.EXE (which provide the user interface code).
Those files call on additional resources such as fonts and miscellaneous
desktop components (like icons and menus), and handle any secondary
settings described in the WIN.INI that were not already processed. This
completes the system startup, and a dialog box is presented so that a user
may log on to the system and begin using it. (Standalone machines may not
have the final prompt if no password is required to use that PC.)
Alternate Startup Methods and Resources
The initialization scenario depicted in the preceding sections details the normal
procedure for starting Windows 98. Technicians and users alike may want to
start Windows using another method for a variety of reasons: to load the
system into a previous version of MS-DOS, to operate in a command-modeonly environment, or to troubleshoot problems. Windows 98 offers two
methods for bypassing the normal startup procedure and gaining access to a
command prompt or safe mode.
The Startup Menu
If the system was shut down improperly, the Startup menu should appear the
next time the operating system loads. It can also be invoked manually by
pressing Ctrl while the system is booting. Choose the appropriate mode for the
desired system startup. The exact options available from this menu vary based
on the system configuration and the reasons for which it was brought up. The
following table shows the most common options and their functions. Note that
the Start In Safe Mode With Network option available in Windows 95 has been
removed in Windows 98.
Menu Option
Normal
Remarks
This invokes the normal startup routine and loads
Windows with all the normal startup files and registry
values in 32-bit mode.
Logged
Runs system startup, creating a startup log file.
(BOOTLOG.TXT)
Safe Mode
Starts Windows, bypassing startup files and using only
basic system drivers. You are provided with minimal
support (including a basic VGA display driver) to allow
troubleshooting and adjustment of the system
configuration files. You can also start this option by
pressing F5 or typing win /d:m at the command
prompt. Booting into safe mode bypasses all secondary
startup files, including the registry, CONFIG.SYS,
AUTOEXEC.BAT, and the [Boot] and [386Enh] sections
of SYSTEM.INI.
Step-By-Step
Confirmation
Starts Windows, allowing you to confirm or disable
startup files line by line. You can also start this option
by pressing F8 when the Startup menu is displayed.
Command
Prompt Only1
Starts the operating system with startup files and
Registry, displaying only the command prompt.
Safe Mode
Command
Prompt Only1
Starts the operating system in safe mode and displays
only the command prompt, bypassing startup files. This
has the same effect as pressing Shift+F5.
Previous
Version of MSDOS
Starts the version of MS-DOS previously installed on
this computer.This is only available on computers
upgraded from a previous MS-DOS environment. You
can also start this option by pressing F4. This option is
available only if BootMulti=1 in MSDOS.SYS.
The Startup Disk
You can also use the startup disk that was created during the initial system
installation or use the Start menu. The startup disk provides the drivers
necessary to access the CD-ROM drive, enable 32-bit file system access, and
start the system in command mode—even if you can't access the hard drive
normally—if it is intact. Booting this way also provides access to a number of
utilities that are covered in Chapter 19, "Maintaining the Modern Computer."
The WIN.COM Command
Once a command prompt is available, you can attempt to load Windows with
the WIN.COM command and one or more of its switches to start Windows 98.
Keep in mind that you may have to provide the path to the command. It is
usually in the C:\Windows or C:\Windows98 directory. The following table
shows the WIN.COM syntax and the uses of the switches.
Switch
Purpose
/d
Used to start Windows in safe mode with one of the following
options to troubleshoot the operating system.
/f
Disables 32-bit disk access. This is equivalent to disabling the
hard disk controller(s) in Device Manager. Try this if the
computer appears to have disk problems or if Windows 98 stalls.
This is equivalent to 32BitAccess = FALSE in SYSTEM.INI.
/m
Starts Windows 98 in safe mode.
Specifies that Windows 98 should not use ROM (read-only
memory) address space between F000:0000 and 1 MB for a
/s
break point. Try this if Windows 98 stalls during system startup.
This is equivalent to SystemROMBreakPoint = FALSE in
SYSTEM.INI.
/v
Specifies that the ROM routine will handle interrupts from the
hard disk controller. This is equivalent to VirtualHDIRQ = FALSE
in SYSTEM.INI.
/x
Excludes all of the adapter area from the range of memory that
Windows 98 scans to find unused space. This is equivalent to
EMMExclude = A000-FFFF in SYSTEM.INI. If this switch resolves
the issue, you may have a conflict in the upper memory area
(UMA) that requires an Exclude statement.
The BOOTLOG.TXT File
Windows 95, Windows 98, Windows NT, and Windows 2000 all provide the
ability to create a boot log. One of the Start menu options offers the ability to
generate this file as the system is started. It is not unusual to have this file
run as long as 15 or 20 pages on even a simple system. The following sample
shows portions of an actual BOOTLOG.TXT file. As you can see, it depicts in
sequence each action the start process makes and whether or not it executes
successfully. This file is a powerful tool for determining exactly where a
problem with a driver or setup process occurs. In the event of an obscure or
difficult problem loading the operating system, it can prove invaluable. We
discuss its use further in Chapter 19, "Maintaining the Modern Computer."
[000820DF] Loading Device = C:\WINDOWS\HIMEM.SYS
[000820DF] LoadSuccess = C:\WINDOWS\HIMEM.SYS
[000820DF] Loading Device = C:\WINDOWS\DBLBUFF.SYS
[000820F1] LoadSuccess = C:\WINDOWS\DBLBUFF.SYS
[000820F1] Loading Device = C:\WINDOWS\IFSHLP.SYS
[000820F1] LoadSuccess = C:\WINDOWS\IFSHLP.SYS
[00082117] Loading Vxd = VMM
[00082117] LoadSuccess = VMM
[00082116] Loading Vxd = msmouse.vxd
[00082116] LoadSuccess = msmouse.vxd
[00082116] Loading Vxd = dynapage
LoadStart = C:\WINDOWS\fonts\symbole.fon
LoadSuccess = C:\WINDOWS\fonts\symbole.fon
LoadStart = C:\WINDOWS\fonts\smalle.fon
LoadSuccess = C:\WINDOWS\fonts\smalle.fon
LoadSuccess = user.exe
Init = Final USER
InitDone = Final USER
Init = Installable Drivers
InitDone = Installable Drivers
Terminate = User
Terminate = Query Drivers
EndTerminate = Query Drivers
Terminate = Unload Network
EndTerminate = Unload Network
Terminate = Reset Display
EndTerminate = Reset Display
EndTerminate = User
Lesson Summary
The following points summarize the main elements of this lesson:
Windows 98 is a true 32-bit operating system, which builds on Windows
95 and adds improved performance, reliability, and support for Plug-andPlay technology.
The operating system can be broadly broken down to two major
components: the core and ancillary systems. The core consists of four
components: the GDI, the kernel, the user component, and the user
interface.
The WDM allows a single driver to be used across a range of Windows
operating systems, including Windows 98, Windows Me, and the various
editions of Windows 2000. The WDM architecture is arranged in a series
of layers, with a hardware device at the bottom and the applications using
it at the top.
The Windows 98 boot sequence can be broken down into three broad
phases: the BIOS initialization phase, the hardware profile and real-mode
driver loading phase, and the protected mode initialization phase.
The Windows 98 boot sequence takes over after the POST and concludes
with turning the system over to the user interface.
Although you can still make use of the AUTOEXEC.BAT and CONFIG.SYS
files, their functions have been incorporated directly into the Windows 98
operating system startup processes.
Safe mode is a means of operation that can be used to troubleshoot a
Windows 95 or Windows 98 operating system that fails to load properly.
3 4
Lesson 2: How Windows 2000 Works
This lesson explains the basic design of the Windows 2000 system
architecture, how the operating system manages tasks, and the entire system
boot process. You should be familiar with the material in this lesson before
proceeding to Lesson 3.
After this lesson, you will be able to
Understand the Windows 2000 system architecture
Understand how Windows 2000 Professional handles tasks and allocates
memory
Identify the elements of the boot process and core files of Windows 2000
Estimated lesson time: 55 minutes
The Windows 2000 System Design
To the casual observer the Windows 2000 and Windows 98 operating systems
may appear virtually identical. They share a common user interface, use
similar file naming conventions, and come from the same manufacturer.
However, Windows 2000 is a radically different environment from Windows 98.
A quick examination of some of its advanced features highlights how much
more robust the design is:
Windows 2000, like its Windows NT predecessor, is able to run on both
CISC (complex instruction set computing, like the Intel Pentium) and
RISC (Reduced Instruction Set Computing, like the DEC Alpha)-based
CPUs.
It provides SMP (symmetric multiprocessing) support, allowing the system
to use more than one processor at the same time. Windows 2000
Professional supports two processors per platform and other versions in
the Windows 2000 family can operate up to 32 processors at the same
time.
Windows 2000 can operate applications written both to the Win32 and
the POSIX (Portable Operating System Interface for UNIX) environment.
The Windows NT advanced file system and other elements of the Windows
2000 environment offer security features not found in Windows 95,
Windows 98, and Windows Me.
A variety of advanced management and customization tools provide the
user much more control over the Windows 2000 environment than that
found in Windows 98.
Windows 2000 Professional is built on the same core technology as the
Windows 2000 Server platforms, based on Windows NT technology,
offering advanced networking controls not found on simple peer-to-peer
platforms like Windows 98 and Windows Me.
Two Modes, Several Subsystems
As an operating system, Windows 2000 can be divided conceptually into the
kernel mode and user mode, each containing several subsystems. Functionally,
it helps to visualize the entire operating environment as a series of layers. The
bottom layer is the physical hardware itself, above that is the kernel mode, on
top of that the user mode, and above that rests the applications that use the
services provided by the operating system. Figure 18.2 provides a graphical
representation of this model. It focuses on Windows 2000 Professional, but can
be extended all the way to Windows 2000 Datacenter Server. Keep in mind
that many of the server functions of the advanced editions of Windows 2000
may require additional components.
Figure 18.2 The Windows 2000 Professional operating system architecture
Kernel Mode
The kernel mode is the portion of the operating system that has direct access
to both the physical hardware devices and the system data that runs on it.
This is the layer that provides access to memory and prioritizes access to
system resources like memory and hardware devices, so its operations are
contained in a protected memory area. The kernel mode consists of several
components.
Hardware Abstraction Layer
The hardware abstraction layer (HAL) is the key to Windows 2000's ability to
support multiple processors and to run on platforms built on different CPU
architectures. The HAL is responsible for operating the interface among all the
different I/O devices on the system, interrupting controllers, and providing
platform-specific hardware support for every device on the system. This
component operates basically the same way it did under Windows NT.
Windows 2000 Executive
The Windows 2000 Executive acts as the interface between the HAL and the
system components contained in user mode. The components of the Windows
2000 Executive provide core services through a set of internal routines that
make sure that two devices, like an application, virtual machine, or CPU, are
not allowed to access the same device at the same instant. You can see from
the descriptions of Windows 2000 Executive components that follow that the
operating system processes in Windows 2000 are more compartmentalized
and, therefore, more fault-tolerant than similar functions found in Windows 98
and Windows Me. They are also more extensive.
The I/O Manager processes commands issued through the user mode into I/O
request packets and services I/O operations related to device drivers. Its
subcomponents include the Cache Manager, which improves disk performance
by performing reads to disks in the background and holding recent disk reads
in system memory, and low-level device drivers that directly manipulate
hardware I/O.
The GDI and Window Manager are the two Windows 2000 System Executive
components that manage the display system. Both are contained within the
WIN32K.SYS device driver. The GDI component manages the functions
required for drawing and manipulating graphics on the screen or graphics that
are output directly to devices like a printer. The Window Manager controls
screen output and window displays, as well as accepting and forwarding signals
from the keyboard and pointing devices to the active application.
Client/server communications are the province of the Interprocess
Communications (IPC) Manager. The IPC subsystem requests information from
the server functions of the Windows 2000 Executive. The IPC has two
components: The local procedure call (LPC) facility handles client/server traffic
that exists within a single computer, and the remote procedure call (RPC)
facility manages client/server traffic that takes place between two or more
computers.
The Security Reference Monitor (SRM) is responsible for enforcing all security
policies that are in force on the local computer.
During its operation, Windows 2000 creates a variety of transitory objects
including processes (programs or part of a program), threads (a specific set of
program commands that can be operated independently), and data structures.
The Object Manager is the kernel mode component responsible for keeping
track of all these objects during their life span. The actual creation and ending
of threads and processes is the task of the Process Manager.
The Plug-and-Play Manager coordinates the operation of Plug-and-Play device
drivers among the HAL, the Windows 2000 Executive, the appropriate
interface or system buses, and the relevant device drivers. During boot, and in
the event of the discovery of new or removed devices, it manages device
configuration and initialization or removal of drivers and coordinates their
availability with the user mode components.
The Power Manager performs a similar function with power management APIs,
coordinating events, generating IRPs (Interrupt Request Packets), and starting
and stopping devices that make use of power management functions.
The Virtual Memory Manager provides a private virtual memory address space
for each process or thread and protects that space against encroachment by
other system objects. The Virtual Memory Manager controls this function for
both physical RAM and hard disk space, as well as managing demand paging.
These concepts should already be familiar from our discussion of Windows 98.
Kernel Mode Drivers
The structure and function of device driver operations within Windows 2000 is
much more complex than that found within Windows 98. In general, hardware
devices are objects managed by the I/O Manager, and the logical, physical,
and virtual drivers for devices are represented as objects within the system.
Kernel mode drivers act as an interface between the HAL and the Windows
2000 Executive. The direct control of these drivers is the province of the I/O
Manager.
Kernel mode drivers are divided into three layers based on their function and
how close they come to directly controlling the hardware.
Low-level drivers are usually used to exert direct physical control over
devices like a Plug-and-Play hardware bus. This class of drivers also
includes legacy Windows NT device drivers.
Intermediate-level drivers include WDM drivers like those discussed in the
preceding lesson that are employed with Windows 98. These are generally
Plug-and-Play function drivers designed to control specific peripheral
devices and mini drivers, and they are used for tasks like disk mirroring.
High-level drivers include those that operate translations between
different file system devices such as FAT, NTFS, and CDFS (CD-ROM File
System) and the operating system. This class of drivers is known as file
system drivers. They cannot act on their own; they depend on support
from one or more intermediate-level drivers.
User Mode
User mode can be thought as a layer of insulation between kernel mode and
users and their programs. User mode handles all conversations with the kernel
and provides the APIs needed to emulate application and network
environments. It is the user mode that enables Windows 2000 to run
applications written for Windows 95, Windows 98, MS-DOS, and POSIX. User
mode is comprised of a series of subsystems.
There are two primary groups of subsystems: integral and environmental. A
good example of the former is a security subsystem, which manages logon
requests from users. It manages all the rights and permissions granted to user
accounts and controls access to resources. Environmental subsystems might be
thought of as the final layer. The most common is the Win32 environment,
which acts as an intermediary between legacy Win16 and MS-DOS applications
and controls and Win32-based applications running in a Windows 2000
environment.
The Windows 2000 Boot Process
In many ways, the Windows 2000 Professional boot process is different from
that encountered with Windows 98. It is, however, very similar to the process
of initialization used by Windows NT. The process can be broken down into
seven segments, from turning on the power to presentation of the logon
screen. The following sections detail them and describe the key files needed to
initialize Windows 2000 Professional operation.
System Start and POST
This phase of system startup is identical to that of Windows 98, as this portion
of the process is hardware dependent.
BIOS Initialization and Operating System Detection
This phase also is directly under control of the hardware and behaves just as it
does in Windows 98. The system BIOS institutes a search for an operating
system. In most cases, it searches first on the floppy drive, then the system
hard disks. It searches the active partition of the first hard drive and looks for
code that loads an operating system. When the Windows 2000 code is located,
the startup routine diverges from that of Windows 98 and Windows Me.
Bootstrap Loading
Microsoft Windows 2000 does not automatically assume that it is the only
operating system on the computer. It also does not require that all the primary
files reside on the primary partition of the first hard drive, as is the case with
MS-DOS, Windows 95, Windows 98, and Windows Me. Instead, it uses a
bootstrap loading process to allow the user to choose which operating system
to initialize and to locate the required operating system files.
The primary partition of the boot drive on a Windows 2000 computer contains
at least four system-specific startup files, and as many as eleven.
These files must be present in the root directory:
NTLDR
BOOT.INI
NTDETECT.COM
CDLDR
This file must also be present in the root on multiple boot systems:
BOOTSEC.DOS
This file may exist on systems with very large SCSI or EIDE drives:
NTBOOTDD.SYS
These files may be in either the root directory or in a subdirectory of the
WinNT directory on another drive if you elected to install the operating system
on a second drive:
HYBERFILL.SYS
NTOSKRNL
HAL.DLL
SYSTEM KEY
Various Device Drivers Needed to Launch the Operating
System
NTLDR is responsible for offering a menu with the available operating systems,
for taking action based on the selection, and for performing the startup
procedures that must take place before the kernel is loaded. To do so, it
performs the following tasks:
It forces the CPU(s) into 32-bit flat memory mode.
It identifies the type of file systems on the drive (NTFS and/or FAT) and
initializes access to the appropriate code to read files on the system.
It inspects the BOOT.INI for entries that indicate if there is more than one
operating system available. If so, it offers a menu allowing the user to
select the appropriate operating system. The following listing shows the
contents of a BOOT.INI file that offers loading Windows 2000
Professional, the location of the system files (in this case the first
partition of the first hard drive), and the Windows 2000 Professional
Recovery Console. A 30-second delay is provided before the default
system is started.
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINNT
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINNT="Microsoft Windows 2000 Pr
C:\CMDCONS\BOOTSECT.DAT="Microsoft Windows 2000 Recovery Console /cm
If the user selects an operating system other than Windows 2000 Professional,
control is passed over to the BOOTSECT.DAT file. In the example above, it
invokes the Recovery Console located in C:\Cmdcons. During this phase, the
user may also invoke the last known good configuration or choose an alternate
boot process to perform troubleshooting tasks. If the user does not,
NTDETECT.COM is invoked to handle the initial hardware detection phase.
NTLDR remains in operation throughout this process.
Hardware Detection and Configuration
NTDETECT.COM examines the system and reports back, providing the
computer ID, hard drive adapter type, graphics adapter, keyboard and pointing
device, types of communications and parallel ports, and presence of a floppy
drive. In the unlikely event that more than one hardware profile has been
established for this machine, the user is offered the option of selecting one at
this point. (Hardware profiles are usually only necessary in the event that
there is legacy non-Plug-and-Play hardware present on the machine.)
Loading the Kernel and Preparing to Accept the User
NTLDR begins loading the kernel and the hardware abstraction layer into RAM.
At this point, control is passed to the kernel and the user is presented with the
Windows 2000 Professional Startup screen. The NTOSKRNL file examines a
configuration and collects information about network logons and connections.
The kernel service controller starts any system services that are configured to
load automatically, and the registry settings for hardware operation of the
local machine are confirmed and initialized. At this point, the user logon
screen appears.
User Logon
Windows 2000, like Windows NT, requires a user to actually log on before
system startup is complete. To do so, press Ctrl+Alt+Del and enter any
appropriate user account name and password. Windows 2000 provides for two
types of users: local and workgroup, or domain.
Local accounts, as the name implies, are those set up directly on the system.
The local security subsystem verifies the user account, checks the password,
and grants or denies access based on local settings. Workgroup and domain
accounts reside on a security server, often a domain controller. The account
information and user rights are then verified at the server or an authorized
alternate location. Once the account has been validated using one of these
methods, the system is operational.
Lesson Summary
The following points summarize the main elements of this lesson:
Windows 2000 is a radically different operating system, in both function
and design, than Windows 98.
Windows 2000 is built on the core technology found in Windows NT.
The Windows 2000 environment is composed of a series of layers that
link hardware to applications. It can be broken into two primary
segments: the kernel mode and the user mode. Each of these is
comprised of a series of subsystems or components.
Kernel mode is responsible for talking with the physical hardware and
managing primary device drivers. It also includes the Windows 2000
Executive, which communicates with user mode.
The Windows 2000 boot process is significantly different from that of
Windows 98 or Windows Me. It is similar to that for Windows NT.
The Windows 2000 start procedure begins with system power up or
restart and finishes only when a user successfully logs on.
Most of the initial startup process is under the control of the NTLDR
program until the kernel is loaded.
3 4
Lesson 3: Managing Windows
This lesson covers configuring Windows. It builds on the information in the
preceding lessons, and it is necessary to understand the material presented in
Chapter 19, "Maintaining the Modern Computer." You should follow this lesson
at a computer running either Windows 98 or Windows 2000 Professional. The
lesson covers both operating systems.
After this lesson, you will be able to
Understand the functions of the Registry Control Panel and the Microsoft
Management Console
Understand how to configure system settings and add new hardware
using the Control Panel
Understand basic use of the Windows 2000 Administrative Tools
Know the fundamentals of how to edit the Registry
Estimated lesson time: 50 minutes
Introducing the Windows Registry
Most end users rarely need to adjust system settings or add new hardware to
their computers. The majority of routine maintenance and simple repair tasks
they need to attend to can be accomplished with the assistance of wizards
found in both Windows 98 and Windows 2000. As a technician, however, you
need to be familiar with the System Registry and the tools used to work with
it: the Windows Control Panel and, in the case of Windows 2000, the Microsoft
Management Console (MMC). You will use them on a regular basis to
configure, fine tune, and repair your clients' computers.
NOTE
The information presented in this lesson serves as more of an
introduction than a tutorial. Fully covering all aspects of
configuring and managing the Windows environment is beyond the
scope of this book. It is recommended that you consult the
appropriate Microsoft Resource Kits for the operating systems you
work with. These publications include in-depth training and
reference materials for the various settings and their uses.
Microsoft Windows treats all the devices, device drivers, software services, and
applications that use it as objects. The System Registry tracks and makes
available to the kernel information on all the those objects, hardware, network
settings, user preferences, and storage systems—virtually everything related
to system operation.
A Major Change in Approach
Windows 3.x made use of two kinds of initialization (.ini) files: system and
private. System initialization files were used to control the Windows
environment and included SYSTEM.INI and WIN.INI, and their settings were
globally available. Private initialization files were more specific in scope and
included CONTROL.INI, PROGMAN.INI, WINFILE.INI, and PROTOCOL.INI, as
well as any application-specific .ini files. Initialization files created a bridge
between the application and the Windows operating environment.
In addition to .ini files, Windows 3.1 used a host of other text files to manage
operations. The files included two holdovers from MS-DOS: AUTOEXEC.BAT
and CONFIG.SYS. Some systems had more than 150 files responsible for the
operation of the computer and the Windows environment, many of them from
third-party providers. This situation often resulted in confusion and erratic,
unreliable operation. It also made writing drivers and installation routines
much more difficult than necessary.
NOTE
The Registry replaces CONFIG.SYS, AUTOEXEC.BAT, and the old
.ini files used in versions of Windows 95 and Windows 98 and, to a
lesser extent, Windows NT and Windows 2000. Windows 2000 can
still read .ini file settings to provide backward compatibility for
legacy devices and software. However, whenever possible, use of
these files should be avoided.
During the development of Windows 3.11, it became apparent that a move
away from the .ini files was needed. A new file type was introduced into the
programming environment. The file was called REG.DAT, and it was the
precursor to the Windows 95 Registry. REG.DAT included information used for
drag-and-drop operations, OLE (object linking and embedding), and
establishing associations between data files and their programs.
The binary file REG.DAT was bundled with its editor, REGEDIT.EXE. This began
the process of centralizing computer operations, but REG.DAT had serious size
limitations. It could not exceed 64 KB, the same limit established for the .ini
files in Windows 3.11.
Since then, development of the registry concept has matured and, in the
modern Windows 98, Windows NT, and Windows 2000 era, knowing how to
adjust the Registry settings is as critical for a technician as understanding
CONFIG.SYS and upper memory management was in the days of MS-DOS.
A Critical Central Repository
It's convenient to think of the Widows Registry as "data central." During
system startup and regular operation, the kernel, system services, background
hardware detection devices for Plug-and-Play operation, device drivers, and
applications are checking with the Registry to confirm settings. Anytime you
install a new piece of software or hardware, make use of the functions of
Control Panel, or do something as simple as changing the View options used to
control information display in folders, you are modifying the Registry.
If the Registry becomes corrupt or has the wrong data for an object, it can
degrade or even halt system operation. With that in mind, Windows provides
work tools and safeguards to make it easy to safely modify settings, while
ensuring integrity of the Registry files. There are some differences in the
Registry structure and tools provided between Windows 95, Windows 98,
Windows Me, Windows NT, and Windows 2000. In spite of that, it is possible to
learn the basics of working with the Registry for both families of Windows at
the same time. Windows 2000 and Windows NT offer some extra controls and
tools that are not found in the Windows 9x family.
NOTE
For purposes of this discussion, we use Windows 9x to refer to
Windows 95, Windows 98, and Windows Me, unless otherwise
noted. Fully covering all aspects of configuring and managing the
Windows environment is beyond the scope of this book. You should
assemble a library including the appropriate Microsoft Resource
Kits for the operating systems you install and maintain. These
publications include additional training and reference materials for
the various settings and their uses.
The Registry is seen by the operating system as if it was a single data store,
but, in reality it is comprised of several files. Hardware- and applicationspecific settings are stored in one file, user-specific data (such as user profiles)
are stored in another, and system-specific policies (which can be used to
locally override elements of settings in the other two files) form a third. During
system operation, the active elements of the Registry are brought into RAM as
a single repository.
Windows Configuration and Management Tools
The Windows Control Panel
The most commonly used tool for modifying the Registry or adjusting the
system configuration is the Windows Control Panel. The fundamental use and
operation of the Control Panel is virtually the same in all versions of Windows.
There is a slight difference in the organization and number of tools contained
within the Control Panel. The Windows 98 Control Panel contents are very
similar to those in Windows 95. Windows 2000 has some additional folders and
icons. The Windows Me Control Panel is very similar to that of Windows 2000.
Figure 18.3 shows the contents of both the Windows 98 and Windows 2000
control panels. You may wish to work through the rest of this lesson seated at
the computer and follow along with the discussion by opening and examining
the system tools as they are presented. You can open the Control Panel by
accessing the Start menu. Choose Settings, and then choose Control Panel. A
window similar to one of those shown in Figure 18.3 should appear.
Figure 18.3 The Windows 98 and Windows 2000 control panels
As you can see from Figure 18.3, most of the icons are identical in both
editions, and many of these are self-explanatory. For example, the Mouse and
Game Controllers icons are used to define active buttons, define their use, and
perform calibrations.
Working with System Properties
The System Properties icon is one of the most useful Control Panel
components. This utility quickly provides detailed information on the system
configuration and often helps pinpoint components that are not working
properly or do not have properly functioning drivers. To access it, double-click
the System icon, which shows an image of a CPU with monitor, keyboard, and
mouse. Figure 18.4 shows the Windows 2000 Professional System Properties
utility open to the General tab. The General tab is similar for all the different
versions of Windows currently in use, but the other options tabs offered vary.
In some cases, they may vary between two computers running identical
operating systems, depending on the hardware that is installed. All share one
attribute: They quickly let you locate information about specific devices on the
system.
Figure 18.4 The Windows 2000 System Properties dialog box
The General tab provides three basic pieces of information: the version of the
operating system in use; if it is registered and to whom; and a quick run-down
of the CPU, computer type, and amount of RAM on the system. The string of
numbers in the registration information portion uniquely identifies this
installation of Windows and is tied to the registered user. You need this
number to call Microsoft for support in connection with this machine.
If you are following along using Windows 2000, click the Hardware tab, and
then click Device Manager, found in the middle of the window. In Windows 9x,
click the Device Manager tab in the System Properties dialog box. The
Windows 2000 Device Manager window is shown in Figure 18.5. Although the
detailed appearance of the window that now opens may vary based on the
version of Windows being used and the display options set, its basic function
remains the same.
Figure 18.5 The Windows 2000 Device Manager
The Device Manager is one of the most useful tools in the Control Panel. It can
be used to identify the components on the system, determine if they are
considered functional by the operating system, and provide detailed
information about the device driver.
The main portion of the Device Manager window contains a series of icons. If a
plus sign (+) appears to the left of the icon, you can click on it to see devices
and subcategories nested within that listing. For example, in Figure 18.5, both
the Disk Drives and SCSI and Raid Controllers listings are open to show their
contents. In the information bar just above the main window area in the
figure, notice that it says "Device Manager on local computer." This is one
difference between Windows 9x and Windows 2000. With Windows 2000, you
can use Device Manager to manage the Registry on remote computers if you
have the proper administrative credentials to work on the remote system and
it is configured to provide this feature. If your work entails providing support
to remote computers over a local area network (LAN), you may wish to learn
more about this feature.
Right-clicking on a device's icon within the Device Manager window, or within
Windows 9x, and clicking on the Properties button with the icon selected
brings up detailed information about the specific device. Figure 18.6 shows the
details concerning the SCSI hard drive shown in Figure 18.5. The specific
information and options provided when you examine the properties vary based
on the version of Windows and the specific device being inquired about.
Remember that all this information is being pulled directly from the Registry
and, in cases where you can modify the information or adjust a setting, the
Registry itself is being updated with your changes.
Figure 18.6 A typical Device Manager Properties dialog box
This dialog box has tabs of its own, starting with a General tab. Notice the
device status area of this dialog box. If the device is shown as working
properly, it indicates that Windows is satisfied that the driver can communicate
with the device. Depending on the version of Windows and the type of device,
you may be offered a Troubleshooting button. Clicking it will usually activate a
wizard that will walk you through a series of options to try to resolve any
problems you might have with the device.
The Driver tab in Windows 2000, depicted in Figure 18.7, shows how the
Device Manager is increasing in usefulness as Windows matures. Early
versions of the operating system did little more than provide the name of the
driver file and the date it was produced. As you can see, the newest versions
of Windows allow you to inspect more driver details and update or install a
driver directly from within the Driver tab if needed. Device Manager has a
number of wizards that simplify the process of updating driver information and
adding and removing devices in the system.
Figure 18.7 The Device Manager Driver tab
If the device is not working properly, has been disabled, or has produced a
conflict with another device on the system, its icon appears with either a
yellow caution or a red warning circle placed over a portion of the icon. Figure
18.8. shows a number of buttons used for obtaining properties, refreshing the
device list, removing a device, and printing a report. These tabs are found
when working with the Windows 98 Device Manager.
Figure 18.8 The Display Properties dialog box
Alternate Methods of Accessing Control Panel Functions
Windows offers several ways besides the Control Panel to access some Control
Panel functions. For example, right-clicking in any open area of the Windows
desktop and selecting Properties launches the same Display Properties dialog
box. You can also access this dialog box by double-clicking the Display icon in
the Control Panel. This utility allows quick adjustment of display adapter
settings, changes in the appearance of the desktop, and setup of screen savers
and effects. It can be used to troubleshoot display problems, set color depth,
and fine-tune the interaction between the graphics adapter and the monitor.
The Display Properties dialog box is shown in Figure 18.8.
The Windows 2000 Administrative Tools
Windows 2000 provides additional tools beyond those found in Windows 98.
The easiest way to access these tools is to open up the Administrative Tools
folder found inside the Windows 2000 Control Panel. Figure 18.9 shows the
basic contents of the Administrative Tools folder. Windows 2000 ships with a
common set of administrative tools, but these are only a starting point. Thirdparty vendors and administrators can build custom consoles and utilities called
snap-ins.
Figure 18.9 The Windows 2000 Administrative Tools folder
Using the MMC
The MMC provides an easy means of centralizing system administration,
managing tasks, and troubleshooting system problems. Figure 18.10 shows a
typical Windows 2000 computer management console. It is accessed in the
Administrative Tools folder by double-clicking the Computer Management icon.
The MMC can be used in conjunction with the Task Scheduler to automate
routine tasks. A technician can perform many system support tasks using the
tools in the Control Panel, but the MMC generally offers easier access and
provides some utilities not available as first-level icons in the Control Panel.
This is especially true when it comes to managing storage devices.
Figure 18.10 The Windows 2000 Computer Management console
The console shown in Figure 18.10 is open on the Device Manager. The left
window pane shows the tree with the different management applications that
are available. The section of the window on the right provides the same
functionality the Device Manager does when accessed from within the Control
Panel, because the Device Manager has been selected. Right-clicking on a
device in the right panel presents the same dialog boxes and options as the
Device Manger will from the Control Panel.
Clicking System Information on the left side of the MMC displays a tree
structure in the right side of the window, depicting all the devices and services
on the system. You can see that it is very easy to use the MMC to quickly
examine and work on a system.
The time spent learning to use the MMC is time well spent. Microsoft has
shown a commitment to using the MMC as the core of future management tool
development. It offers a single user interface for a wide variety of system
tools, which has become even more important in a network environment. In
addition to the system tools and storage tools shown in our example in Figure
18.10, the server editions of Windows 2000 offer a variety of tools for
administering network, Internet, and server services within the MMC.
Using the MMC to Track System Operation and Performance
During operation, Windows 2000 tracks virtually everything that happens on
the system and writes the information to a series of logs. The Event Viewer
snap-in shown in Figure 18.11 is used to examine three key log files:
The system log contains a listing of all internally generated warnings,
errors, and critical events related the operation of the system.
The security log monitors all attempts to access the system, records
whether they succeed or fail, and tracks any other security parameters
set as part of the system on a policy.
The application log tracks the operation of programs on the system and
contains any errors, warnings, or other events that are specifically
tracked for that application.
As you can see in Figure 18.11, the operation of the Event Viewer is similar to
that for other snap-ins that operate within the MMC. The Event Viewer tree in
the left pane contains three branches, one for each log. Clicking on one of the
branches opens the appropriate log in the pane on the right. The entry
includes the date stamp for the time the event was launched, the source, and
an event code that can be used to aid in troubleshooting or for more
information about the type of event. The leftmost column provides the name of
the type of event. Those most likely to demand operator intervention are
flagged with color-coded icons. In our example, the error messages on the first
two lines have red flags with Xs, indicating the failure of a device. Not all
warnings actually demand intervention. In this case, a removable storage
device merely did not have media installed.
Figure 18.11 The MMC Event Viewer
Microsoft Windows 2000, like Windows NT, offers a wide range of performance
monitoring and tuning tools. These can be set to actively track in real time
virtually every performance indicator of the system, memory usage, and
primary systems (like the display, drives, and system processes). The
information can be presented in a set of graphs or stored in spreadsheet or
database format for later review.
Windows 2000 Disk Management
The MMC serves another important function. The Disk Management snap-in is
used to mount drives, create partitions, set up or convert file systems, and
dynamically allocate storage space. These tools far outperform those found in
the Windows 9x environment, which are based on MS-DOS.
Windows 2000 supports two types of hard disk storage. Basic storage is
identical to that found on most other operating systems. Physical hard drives
are partitioned and then initialized for the use of storage. Basic storage uses a
program like Fdisk to divide the drive into partitions. Once created, these
partitions cannot be modified without destroying the data on them. Dynamic
storage is a method of disk utilization unique to Windows 2000. Drives
initialized using the dynamic method are set up as a single partition that spans
the entire physical disk, but is not limited to a single disk; therefore, a single
volume can span several disks. In addition, you can create mirrored and
striped volumes to improve performance or combine several of these into a
Level-5 RAID (redundant array of independent disks) to increase data security.
All hard drives start as a basic disk, and they can be divided into primary
extended partitions as normal. If you plan on dual booting a system with a
non-Windows 2000 operating system, the primary partition should be
formatted with the FAT file system. Volumes that do not need direct access to
that operating system can be formatted using NTFS and become part of a
dynamic storage environment.
Figure 18.12 depicts the Disk Management snap-in on a system running
Windows 2000 Professional. The system has one dynamic disk, one CD-ROM
drive, and two removable devices contained on a smart card reader. The left
pane shows a typical MMC tree, the top right pane shows the different volumes
on the system, and the pane below shows a graphical representation of the
drives. The user can change the content of each of these views.
Figure 18.12 The MMC Disk Management snap-in in action
When a disk without a partition or formatting is added to the system, it is
displayed in the Disk Manager as a foreign disk. Right-clicking on it invokes a
wizard that allows you to prepare the disk for use and import the new disk into
the system. Basic disks can be upgraded at any time using a similar wizard.
Right-clicking on a disk shows all system information concerning the disk,
including its capacity, space allocation, type, capacity, status, adapter
information, and volume information. Network administrators with appropriate
permissions on a Windows 2000 server can use the MMC to manage disks on
any other computer running Windows 2000 within the province of the domain
or of a trusted domain from any other computer running Windows 2000 on the
network.
Working Directly with the System Registry
Components of the Windows Registry
The Windows 9x Registry consists of six root keys, each of which reflects a
different aspect of the configuration. Windows NT and Windows 2000 make use
of only five of the keys due to differences in the way the system accesses and
holds the Registry in memory.
Like the information display of the MMC, the Registry is presented as a series
of trees and branches arranged in a hierarchical order. Each branch of the
Registry (known as a key) groups information that logically belongs together.
All top-level keys are called root keys and are defined and named by Windows;
these cannot be changed. Root keys are named HKEY_XXX and can be followed
by several subkeys. All other keys in the Registry are subkeys of these six
primary keys. Subkeys can be added, deleted, or renamed. The six primary
keys are described in the following sections.
HKEY_CLASSES_ROOT
In Windows 9x, this section of the Registry defines the standard-class objects
used by Windows. Do not make any changes to this section unless you are
absolutely sure you need to do so! This is a link to the
HKEY_LOCAL_MACHINE\ SOFTWARE\Classes, which provides compatibility
with the Windows 3.1 registration database. This compatibility is important if
you want to run Windows 3.1 16-bit applications in Windows 9x. In Windows
2000, this key contains software configuration data, file class associations, and
any information needed for OLE support.
HKEY_CURRENT_USER
This section serves the same functions in both Windows 9x and Windows 2000.
It defines the current user settings, so it is usually not important for repairing
computers. Personalized information like fonts, some icons, and colors can be
changed here. This is a link to the HKEY_CURRENT_USERS key. This key
provides Windows 9x compatibility to applications using the Windows NT
Registry structure.
HKEY_LOCAL_MACHINE
This portion of the Registry contains all the data for the system's non-userspecific configurations (including every device in the computer). This is the
largest key in the Registry and the portion where you will perform the bulk of
your system edits to optimize Windows performance. Information stored here
includes hardware configuration, peripheral devices, installed software, OLE
compatibility, software configuration, and Windows operating system
configuration. In Windows 9x this data is stored in the SYSTEM.DAT file.
HKEY_USERS
This section of the Registry is where both Windows 9x and Windows 2000 keep
track of different user settings. If your computer is not configured for multiple
users, you will have a single subkey named DEFAULT. If your computer has
been configured for multiple users, two profiles are created when you log on:
HKEY_USERS\DEFAULT and HKEY_USERS\user name\USER.DAT. If it is a twouser system, the other user's settings are held in memory. This makes it
impossible to alter user settings without logging on under that user's name
and password.
HKEY_CURRENT_CONFIG
This key handles Plug and Play and contains information about the current
configuration of a multiple-hardware-configured computer. On Windows 9x
machines, this key works in conjunction with
HKEY_LOCAL_MACHINE\Config\xxxx, where xxxx is the subkey that
represents the numeric value of the current hardware configuration. On
Windows 2000 machines, it contains the data stored with the active hardware
profile, which is used to configure device drivers.
HKEY_DYN_DATA
In Windows 9x, this is the Registry data, which is stored in RAM to speed up
system configuration. A snapshot of all hardware in use is stored here. It is
updated on startup and when any changes are made in the system
configuration file. This portion of the Registry is dynamic. It is where VxDs are
installed, where Plug and Play hardware information is maintained, and where
performance statistics are calculated. Because this information is accessed and
changed constantly, this portion of the Registry is never written to the hard
disk. It resides in the computer's RAM. This key does not exist in Windows
2000.
Accessing and Managing the Registry
Most modifications of the Registry should be done using the Windows Control
Panel in the Windows 9x environment. With Windows 2000, you should use
either the MMC or the Control Panel to modify Registry settings. The fact that
the Registry is the central system configuration repository means it is also a
key system weakness—once it has been corrupted, it's hard to recover settings
if they haven't been backed up. Only very knowledgeable users should directly
view or change entries.
You can view or change the entries using one of the two Registry editors that
ship with Windows 2000, REGEDT32.EXE or REGEDIT.EXE. Only the latter is
included with Windows 9x. The Registry itself is stored in binary format, so you
can't open, view, or edit the contents directly. Don't look for either editor on
the Start menu because they are considered too potent for the average user.
You must enter the appropriate command name in the Run dialog box to start
the editor. Although both programs ship with Windows 2000, REGEDIT.EXE
lacks a security menu and does not support several commands available in
REGEDT32.EXE.
You edit the Registry in real time using either of these editors. As soon as you
enter a setting, the effect of your action is immediate. During the remainder of
this lesson, some examples are shown with the Registry editor open. Be sure
not to make any modifications to the Registry itself without being sure of the
actions being taken.
CAUTION
Editing the Registry directly can cause serious problems if it is not
done correctly. Windows provides the Control Panel, MMC, and
Properties dialog boxes for editing the Registry. Microsoft
recommends these methods rather than direct editing of the
Registry. There are some occasions when may it be necessary to
edit the Registry, however, if the system or an application failure
totally corrupts a Registry key. If you must edit the Registry,
follow all the appropriate procedures for backing up the Registry
data and preparing for recovery in the event something goes
wrong. Even then, it may not be possible to perform a total
recovery. Edit the Registry only as a final resort in the event of a
major system failure.
Using REGEDIT with Windows 9x
If you feel you must edit the Registry, then back it up first (see Chapter 19,
"Maintaining the Modern Computer," for details on backing up the Registry).
The tool used to edit the Registry is REGEDIT.EXE (see Figure 18.13). This
program is not included in any of the menus and is not found on the desktop.
You must activate REGEDIT.EXE by locating the executable file in the Windows
directory in Windows Explorer or by starting the program from the command
line using the Run dialog box from the Start menu.
Figure 18.13 REGEDIT open in Windows 98
The following table provides an overview of the commands in REGEDIT.
Menu
Commands
Remarks
Import
Registry Registry
File
Allows you to import a Registry file that youve
created or modified into the current Registry.
Importing a Registry file is often the best way to
rescue a corrupted Registry or to replace a
damaged Registry with a known good backup.
Export
Registry Registry
File
Allows you to export a copy of the Registry file to
a floppy disk or network location. Exporting a
Registry is a crucial step when backing up a
Windows 9x system.
Connect
Registry Network
Registry
Allows you to connect to a user on your network
and, if you have the proper authority, modify that
users Registry entries. This is a very powerful
feature, but not necessarily one that a majority of
users should have access to.
Disconnect
Registry Network
Registry
Releases the connection to a network users
Registry.
Registry Print
Allows you to print either the entire Registry or
one of its keys or branches.
Edit
New
Lets you create keys and assign values.
Edit
Delete
Lets you delete a key, key value, or value name.
Edit
Rename
Lets you rename either a key or value name.
Edit
Find
Finds a particular string or key value name.
Edit
Find Next
Finds the next value that was defined in the Find
command.
View
Status Bar
Either hides or shows the status bar at the bottom
of the screen.
View
Split
Lets you move the split bar (vertical separation)
between the Key window (on the left) and the
Value window (on the right).
View
Refresh
Refreshes the REGEDIT screen.
NOTE
The Edit command doesn't include the typical Copy, Cut, and Paste
options. If you need to copy and paste in REGEDIT, you need to
use the Windows keyboard commands. Press Ctrl+C for Copy and
Ctrl+V for Paste. These two commands are a necessity if you do a
lot of searching and replacing in the Registry.
REGEDIT's Dual Purpose
REGEDIT is more than a Windows utility program. It can be used from inside
real-mode MS-DOS. This is particularly important if you have a seriously
corrupted Registry file and Windows won't start. During installation, Windows
9x puts a copy of REGEDIT.EXE on the startup disk. When running REGEDIT in
real mode, it doesn't have an interface—it uses a command-line format to
carry out instructions. The following table lists the most common REGEDIT
switches.
Switch
Function
/?
Displays the REGEDIT command-line syntax
/L:system
Provides the location and filename of SYSTEM.DAT
/R:user
Provides the location and filename of USER.DAT
/E filename
<regpath>
Creates a Registry (.reg) file
/C filename
Replaces the entire Registry with the contents of
your .reg file
To use REGEDIT in real mode, you need to tell it where your SYSTEM.DAT and
USER.DAT files are located, if they are in a directory other than Windows.
These are the two key Windows 9x Registry files. Here is the syntax needed to
replace an existing, corrupt Registry with the contents of the .reg file you
created (remember, this command is typed in full at the MS-DOS prompt):
REGEDIT [/L:system] [/R:user] /C filename
Using REGEDIT to Modify the Registry
Remember that before modifying any critical keys in Registry, you should
always create a back-up. When you edit the Registry, consider using the
Control Panel applications to make Registry edits. The Control Panel is
essentially the wizard for updating specific parts of the Registry. A corrupted
Registry is not something you can easily recover, and the system may be
rendered useless.
You can make edits directly to Registry using either the menu bar commands
or the right mouse button. Add keys by simply right-clicking the key you want
to add to and entering your information. Windows 9x has some restrictions
you need to be aware of when adding keys:
You cannot add a top-level key. Windows 9x creates these and you cannot
modify the existing entries or create new ones.
Within a parent key, each subkey name must be unique, but you can use
the same subkey name in different parent keys.
Modifying the value section of the Value entry by double-clicking the
value in the Value window. After you double-click the value, you will see
one of three different dialog boxes.
Windows 9x uses multiple registries for multiuser operations, and it can
be difficult to know exactly where pieces of information are stored. The
System Policy Editor allows network administrators to locate where
information is stored.
Editing the Registry with REGEDT32 in Windows 2000
You can use REGEDIT to perform basic Registry modification tasks in Windows
2000, but it is not recommended. REGEDT32 is the editor of choice if you must
modify the Registry directly. Its menus and commands are quite simple,
belying the program's power. The following table provides the primary
commands, their locations, and a brief description of how they are used. The
rest of the menus and options are either demonstrated in the following
exercise, covered in the REGEDIT.EXE material, or are easy enough to
understand by their names and menu locations.
Command
Menu
Remarks
Searches the Registry for a specific key. Its scan begins
active key and looks in all listings below that.
View
Find Key
Registry
Saves the currently selected key and all subkeys in bina
Save Key resulting file can then be used with the Restore comman
values after testing a modification of the Registry.
Registry
Save
Subtree
As
Registry
Windows 2000 administrator can gain access to remote c
this command. Windows 2000 systems allow access by a
Select
account on the system. A valid user is defined as someon
Computer Registry setting with a value of 1 in the HKEY_LOCAL
MACHINE\SYSTEM\CurrentControlSet\Control\SecurePip
key of type REG_DWORD.
Registry
Restore
Saves the current key and other keys in text format. Thi
actually usable by the Registry and cannot be converted
data.
This loads the data in a file created with the Save Key co
the currently selected key and overwrites the existing en
CAUTION
The Registry file in Windows 2000 is much larger than that in
preceding versions of Windows. As a result, it cannot be backed up
as simply as in Windows 98. Recovery procedures are detailed in
Chapter 19, "Maintaining the Modern Computer," and should be
followed before any attempt to actually edit core components of
the Registry.
Using REGEDT32 to Examine the Registry Contents
With a little care, REGEDT32 can safely be used to examine the Registry.
Launch the program by clicking Start, then clicking Run, and then typing
Regedit32 in the Run dialog box. A window should open on your desktop
similar to the one shown in Figure 18.14. As you can see, this editor opens
each key in its own window. The branches are contained in the left pane and
the content is displayed in the right pane.
We are now going to take a step that you should take every time you use
REGEDT32 or REGEDIT. Open the Options menu and adjust the Read Only
option so that there is a check mark in front of it. Remove the check mark
from in front of Save Settings On Exit found below it. This precaution prevents
you from saving any changes you make.
Choosing a Registry Section
The subwindows inside the main Registry Editor window each hold one of the
five files used by Windows 2000 to store the registry data. Choose the one
labeled HK_USERS on Local Machine, and work your way down the hierarchy
to the Default\Control Panel\Mouse folder. With the mouse folder selected, you
should see a display similar to that shown in Figure 18.14.
Figure 18.14 The HK_Current_User On Local Machine mouse settings shown
in REGEDT32
From reading the entries, it is quite easy to see why editing the Registry is not
a job for amateurs, and why most settings should be managed from the
Control Panel. Most of the mouse settings are the same ones controlled by the
Control Panel Mouse utility. Figure 18.15 shows one of the tabs in the Mouse
Properties dialog box that controls three of the settings. The Snap To Default
option in Figure 18.15 is not selected. In the Registry editor, the
SnapToDefaultButton: REG_SZ: has a value of 0. If you access the Mouse
Properties dialog box and enable Snap To Default, the value in the Registry
changes to 1. If you change the value in the Registry manually to 1, the Snap
to Default check box in the Mouse Properties dialog boxes becomes checked.
Obviously, changing a simple mouse setting in error is not likely to bring the
average machine running Windows crashing down. Still, it is not wise to make
changes to the Registry without knowing exactly what the effect is, and the
exact setting and syntax necessary to gain the desired effect. For example, the
range for setting mouse double-click speed is quite wide. In our example, it is
currently set to 500. Without a reference, it would be difficult to know exactly
what the correct range would be.
Figure 18.15 Local machine mouse settings as shown in the Mouse Properties
dialog box
In spite of warnings about the dangers of editing the Registry, the ability to do
so is a valuable tool for a technician. In some cases, it is possible make
adjustments to the Registry that can save hours of work on rebuilding a
system. To become proficient, you should obtain a reference detailing the
Registry settings and a manual with further instructions on editing techniques,
then practice on a system that is not being used for critical work.
Lesson Summary
The following points summarize the main elements of this lesson:
The structure and function of the system Registry is basically the same
for all versions of Windows after Windows 95.
The Registry is a database stored in a binary format containing all the
details of the system configuration.
The preferred way to edit the Registry is to use configuration tools such
as the Control Panel and the MMC.
In the event the Registry must be edited manually, you must do so using
the appropriate editor for your version of Windows.
Addition of elements to the Registry should be handled by properly
trained technicians with an appropriate reference.
3 4
Chapter Summary
The following points summarize the key concepts in this chapter:
How Windows 98 Works
Understanding the boot process for both the computer hardware and the
operating system is key to being able to properly maintain and
troubleshoot a system.
Windows 98 is built on the foundation of MS-DOS and earlier versions of
Windows and uses similar startup files.
Although it is still possible to use configuration files like CONFIG.SYS and
AUTOEXEC.BAT to manage Windows 98 system settings, they should only
be used if necessary for legacy data.
How Windows 2000 Works
Windows 2000 is a completely different operating system from Windows
98, even though the user interface is virtually identical and both
operating systems can share many drivers.
The Windows 2000 system architecture is much more modular in design
than Windows 98 and has a completely different set of core files to bring
the operating system online.
Managing Windows
Both Windows 9x and Windows 2000 use the Registry to enable system
configuration.
The Control Panel and MMC are the preferred ways to edit settings within
the Registry. The Registry should not be modified directly unless it
impossible to do so with those tools.
The Registry is a database stored in binary format.
In the event that the Registry must be edited manually, use the editor
provided with the operating system specifically for this purpose.
3 4
Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. What are the core components of the Windows 98 operating system?
2. What is the kernel, and what is its function within the operating system?
3. What is the VMM?
4. What is virtual memory, and what are its benefits?
5. What is the definition of WDM, what is it, and why is it important?
6. What is a minidriver?
7. Briefly explain the two core files needed to boot Windows 98.
8. Can you use CONFIG.SYS and AUTOEXEC.BAT in Windows 98? Are there
any special considerations?
9. What is the purpose of the NTLDR program in Windows 2000?
10. What is the purpose of the BOOTLOG.TXT file?
11. What is the HAL, and what is its function?
12. Define the Registry.
13. What is the MMC?
14. What is the preferred editor for working with the system Registry and
Windows 2000?
Answers
3 4
Chapter 19
Maintaining the Modern Computer
About This Chapter
The modern personal computer and its operating system are a far cry from the
earliest PCs. The array of sophisticated hardware and the advanced features of
the Microsoft Windows environment have become essential parts of everyday
home and office life. Keeping this vital tool running efficiently requires the
right skills, the right tools, and regular routine maintenance. Properly
performed regular maintenance can prevent problems.
This chapter deals with the necessary tools and general practices used in
performing such maintenance. Keep in mind that your situation may call for
different programs than the one presented here, based on the user population,
system configuration, and the tasks for which the computers are used. The
information in this chapter is based on the average desktop workstation.
Complicated networking environments for advanced operating systems may
entail additional procedures.
Before You Begin
Before starting this chapter, you should read the previous chapters that cover
the physical components of a computer and the fundamentals of the Windows
operating system. In addition, if you are unfamiliar with the procedures for
dealing with the risks of electrostatic discharge (ESD), you should review
Chapter 22, "The Basics of Electrical Energy," especially Lesson 2,
"Electrostatic Discharge."
3 4
Lesson 1: The Right Tools for the Job
In this lesson, we look at the tools and resources needed to function effectively
as an A+ certified computer technician. Working on computers requires tools
and resources in addition to skill. The material in this lesson details the
elements of an A+ technician's toolkit. We also review the basic safety
considerations that are part of the job when working with electrical and
electronic equipment in a repair facility.
After this lesson, you will be able to
Identify and describe the basic tools required to be equipped for working
on computers
Describe the outside resources available to make your work more
productive and effective
Explain the safety considerations and basic policies to be used when
working with computer equipment
Estimated lesson time: 20 minutes
Assembling a Complete Toolkit
Knowledge, preparation, and having the right tools for a task are the primary
ingredients for a successful, efficient, and profitable maintenance activity,
system upgrade, or computer repair. Before attempting any work on a
computer, you should have a good understanding of the procedure or problem
at hand. Ten minutes to an hour of preparation can save hours of endless
guessing and frustration.
One thing that can make any job easier is having the right set of tools and
reference materials on hand at all times. With the availability of information
on the Internet and CD-ROM, plus the expansion of the laptop into a fullfledged computer, it's easy to carry a whole library in a small bag and have
online access to virtually any driver you might need.
Tools of the Trade
Nothing is more important than having the right tools for the job. Being an
effective computer professional requires owning or having access to four sets
of tools:
Hardware toolkit. Common hand and electronics repair tools. Use this to
take things apart and put them back together.
Software toolkit. Use this to troubleshoot and correct operating
systems, hardware, drivers, and application problems. These days, your
software toolkit should also include good, routinely updated virus
checkers and a bootable disk with key diagnostic and system files for each
operating system you work with.
Technical library. Use this to help you keep track of the ever-growing
base of information and provide answers to "I never saw that before"
problems.
Spare parts. Keep a basic set of the most commonly replaced computer
system components—such as power supply, floppy drive, display card, and
cables—so that they can be easily replaced when you're on location.
When in doubt, exchanging a problematic part with a known-to-be
working part will help you troubleshoot. Be careful to collect only parts
that you're sure work. Exchanging a bad part with another bad part won't
help the troubleshooting process and can even make matters worse. A
"goodie bag" with screws, jumpers, expansion plate covers, and so on can
save time when one goes missing.
Recommended Tools and Resources
A computer professional does not need a large toolbox; only a few basic hand
tools and a handful of floppy disks are required to solve most computer
problems. Most PCs can be opened and most parts removed and replaced with
a pair of screwdrivers. Be careful when working on a proprietary machine,
however—special tools are often required. A small canvas bag or a briefcase is
generally sufficient to carry everything you need.
The following table lists and describes the hand tools that will meet most
needs.
Tool
Description
Two (one large and one small) flathead (regular) and
Phillips (sometimes called a cross) screwdrivers are usually
sufficient. Avoid magnetic screwdrivers. Although they are
Screwdrivers convenient for picking up lost screws, their magnetism can
cause problems. A power screwdriver can be a real timesaver when you have new cards to add to several
machines.
Torx driver
Used to remove the odd star-shaped screws found on some
proprietary computers and components. Sizes T-10 and T15 should meet the needs of most computers.
Nut driver
This variation on the screwdriver fits over the hexagonal
collar on many computer screws. Sizes 3/16-inch, 7/32inch, and 1/4-inch will handle most jobs. Sets with snap-on
heads that can be adjusted for several sizes are handy.
Tweezers
Very convenient for picking up small parts (for instance,
screws). You might consider the long plastic variety; these
don't conduct electricity and hence won't create any short
circuits.
Needlenose
pliers
Can be used to pick up dropped items and to hold or loosen
screws, nuts, and bolts.
Chip
removers
Although optional, these are very useful when changing
video RAM (random access memory) or other (older) RAM
chips that are pushed into a socket.
Tube or
plastic bag
A short plastic tube (with caps on both ends) will keep
for small
parts
loose screws and small parts from getting lost.
Compressed
air
A can of compressed air is helpful to remove dust.
ESD tools
An antistatic wristband is an essential tool. Antistatic mats
and antistatic bags are also helpful to reduce the risk of
ESD.
Multimeter
A small, digital meter that is capable of measuring volts
(alternating current [AC] and direct current [DC]) and
ohms (resistance or continuity) is all that is needed.
Flashlight
A small (bright) light is necessary for illuminating those
hard-to-see places.
Hemostats
Good for picking up and holding small parts. Straight
hemostats will work most of the time. However, curved
ones will get into those small places that the straight ones
cannot reach.
Power-on
self test
(POST) card
A POST card can be used to see what the error messages
during system start are when no data is being sent to the
display.
This combination can save hours of time. It can be used to
download drivers from the Internet. With the right
Laptop,
collection of CDs you can access virtually any system file
blank
that you might need, the help screens for command
floppies, and
syntax, and a wide array of information from the Microsoft
CD-ROM
Knowledgebase. You can use the blank floppies to move
folder
files to and from an ailing computer. Be sure to have a
phone cord to connect the laptop modem to the wall jack.
Recommended Software
Don't feel compelled to carry an entire arsenal of arcane software. At the same
time, assemble a collection of the software that supports the computers you
normally work on. That includes the operating system disks and common
drivers. Use the items that follow as a guide.
Bootable Floppy Disk
You should compile and carry bootable floppy disks for each operating system
that you encounter. These should contain the following files:
ATTRIB.EXE
FORMAT.EXE (.COM)
QBASIC.EXE
COMMAND.COM
HIMEM.SYS
SCANDISK.EXE
DEFRAG.EXE
LABEL.COM
SHARE.EXE
EDIT.COM
MEM.EXE
SIZER.EXE
EMM386.EXE
MEMMAKER.EXE
SMARTDRV.EXE
EXPAND.COM
MSCDEX.EXE
SYS.COM
FDISK.EXE (.COM)
MSD.EXE (.COM)
NOTE
These files will barely fit on one 3.5-inch high-density floppy disk.
Files listed in bold are essential.
The Microsoft Windows 98 and Microsoft Windows Me startup disks are also a
good item to carry. These are bootable disks that load all drivers needed to run
a CD-ROM on most PCs, and they include most of the files just listed as well.
TIP
The utility MSD.EXE is a good diagnostic tool that can determine
which hardware options are installed on a computer system
without the need for you to remove the case. MSD.EXE is also a
great tool for diagnosing software conflicts.
Operating System Disks
Make sure copies of the original operating system CDs or floppy disks are
available. If it becomes necessary to install one or more components that were
left out during the original installation, the computer might require verification
of serial numbers from the original disk before any additional files can be
installed. Microsoft Windows 95, Windows 98, Windows Me, Microsoft Windows
NT, and Microsoft Windows 2000 have associated rescue disks (more about
those in the next chapter) in case there are any problems with corrupt files in
the operating system. It is a good practice to ensure that you have these disks
available.
NOTE
Each Windows 2000 and Windows NT emergency repair disk (ERD)
is unique to the computer for which it was created. Therefore, a
new one must be made for each computer in service and kept up
to date every time the Registry is significantly modified.
Software Utilities
There are many good-quality utility programs available today that allow the
experienced user to find and correct a multitude of problems. However, use
caution when "correcting" a problem that has been identified by the software.
The software might consider something a problem simply because it does not
recognize it, on the assumption that, "if I don't know what it is, it must be
bad." In some cases, the cure is worse than the disease. Also, keep in mind
that one utility will not solve every problem. As a computer professional, you
will do far better to master one good software system than to have a box full
of utilities that you don't know how to run effectively. Don't forget good old
MS-DOS; it is full of useful commands that are often forgotten or never used.
CAUTION
Older versions of utility programs designed to work with MS-DOS
and Windows 3.x can wreak havoc on newer versions of Windows.
Be especially careful if you're running later versions of Windows
95 or Windows 98 that use the FAT32 file system, because many
utilities are designed to handle the traditional FAT16 file system.
You should never run any application to "tune" a system that is not specifically
designed for that version of the operating system. That applies especially to
advanced 32-bit operating systems such as Windows 98 and Windows 2000.
Another required part of the software toolkit is a set of virus-checking and
repairing programs that are compatible with each operating system you work
with. Optional additions are disk and video display diagnostic programs.
Documentation and Manuals
Documentation is another key part of advanced preparation in general, as well
as preparation for specific jobs. If adequate documentation is not readily
available, your first step is to collect or create it. When you finish a job, don't
forget to save an account of what you did, any problems you encountered, and
notes on any follow-up required.
Outside Resources
The computer industry changes so rapidly and is so complex that no one
person can hope to master it. When a client has an urgent problem, and the
answer is not readily apparent, an outside resource may have the answer at
hand. As a technician's career advances, it is important that his or her skills
advance along with responsibility. These are just a few of the reasons to
develop a set of outside resources to increase your base of knowledge.
Don't Stop Learning
Continuing education is vital in the computer-repair business. Attending
seminars, reading books and magazines, and listening are essential parts of
the job. The formal training that you are undertaking should be the beginning
of your technical education, not the end. Remember, you will never know
everything, and it will often seem that as soon as you've mastered a new
technology, it is revised. Knowing how to find the answer is often more
important than guessing or thinking you know it all.
Networking
When you want to increase computers' data-handling capabilities, network
them. Remember that you are not the only person interested in fixing
computers. Take advantage of every opportunity to make connections with
your colleagues in the computer business and in the classroom.
Join a local computer users' group—one can easily be found by asking around
local computer stores. These groups are great places to meet and share
common interests with others.
Make yourself available to other technicians. The person you help to solve a
problem (from your base of knowledge and experience) today will be there to
help you tomorrow. The best time to learn about problems and their solutions
is before they happen to you.
The range of hardware, operating systems, and software available today
makes it impossible for any single person to master every aspect of the
personal computer environment. Your experience base, as you encounter
problems, will be different from that of your colleagues.
Build a network of technicians with different areas of specialization. Share
your specialized expertise with your colleagues and learn from them when the
opportunity and need arises.
Get Connected
Today's computer professional needs to be linked electronically to the Internet.
You need Internet access for e-mail, Usenet newsgroups, and the World Wide
Web. After all, your goal is to make computers work for others, so put yours to
work for you.
E-Mail
E-mail is a useful way to communicate with technical support people and
colleagues. E-mail is asynchronous communication that transcends time zones;
a question can be posed at any time of the day, and answered anytime,
without fear of inconveniencing the other party. It is also a good method for
providing customer service.
Usenet
Usenet newsgroups are good places to acquire detailed information about
computers. In a newsgroup, you can get information from other users. You are
more likely to get a frank opinion than to hear "the company line." There are
thousands of Usenet newsgroups, and hundreds are dedicated to computers.
Be sure to look for FAQ (frequently asked question) lists. They are great for
answering basic questions and giving guidance on how to use a particular
newsgroup.
Newsgroups are also invaluable when you come across a situation that stumps
you. Write up the problem and post it to an appropriate newsgroup (or more
than one, but don't cross-post). You may be amazed at the responses you will
get from helpful colleagues—everything from "try this" suggestions to the
actual solution to your problem from someone who has encountered it before.
The World Wide Web
The Web has quickly become the best place to get computer information. Most
suppliers have a presence on the Web, and they often provide upgrades,
patches, and workarounds for problems users encounter with their products.
Many maintain technical databases full of information about both their legacy
products and the most current ones. This information is usually free, but the
fact that it exists is not always advertised. It is not uncommon today for a
supplier to post a fix or upgrade on its Web site without notifying registered
users.
Finding the correct Web site can often be challenging. A good starting place is
a portal site that caters to technicians who frequently upgrade computers.
These sites help you search for a source for buying parts and have links to the
major computer industry manufacturers.
If you don't have luck with portals, use search engines. You might feel
overwhelmed at first with your search results, because responses can literally
number in the thousands. Learn how to use "advanced" search techniques and
try suppliername.com to find the correct domain (it works more often than
not).
A good example, and an excellent resource, is www.microsoft.com. Go to the
support page and access the Knowledge Base. You will find a wealth of
information regarding Microsoft products. After you find a good source, don't
forget to use the Web browser's Favorites, Bookmarks, or similar features to
organize folders with links to the most useful resources you find online. For
example, you could create folders for technical support by company or product.
Commercial Networks
There are a number of major commercial online networks, such as The
Microsoft Network (MSN), available. Many of the smaller Internet service
providers (ISPs) host forums for computer users, similar to the newsgroups
previously discussed. The difference is that they are private, available only to
the users of the service. They work similarly to a bulletin board system (BBS)
where you can post questions and respond to other postings.
Practice
Knowledge that does not get used gets lost. Practicing is the only way to keep
your skills sharp. However, use caution when trying things out for the first
time or when experimenting (especially on someone else's computer).
Explaining that you crashed because you were "playing" with a new technique
or piece of hardware can be a painful experience for all involved.
However, it doesn't hurt to keep some equipment on hand for the sole purpose
of playing. For many technicians, extra equipment at work is rare and their
personal machines become their test machines, constantly being ripped apart
and experimented on. If a system or two can be kept around for
experimentation and education, you can greatly enhance the value of any
other training you receive and reduce overall costs. Given the cost of PCs
today, a test machine is a worthy addition to your lab.
Read, Read, and Read Some More
Keep up with the computer industry press. There are many good computer
books available, but remember, computer books have a relatively short shelf
life. Magazines and subscription services like Microsoft Tech-Net are great
resources. Don't forget that most print magazines have online editions, and
some excellent magazines exist only online. These e-zines offer in-depth
reviews and industry advice long before it appears in hard-copy publications.
Subscribing to a computer magazine usually means that your name appears on
a number of mailing lists that are sold to computer companies. If you can
overcome sensitivity to privacy issues and tolerate junk mail, the ads that will
begin to fill your mailbox offer another way to keep track of new products as
they become available.
Technical Support
You might ask yourself why you need technical support if you are yourself an
A+ technician. The answer is simple: You can never know everything. The
ability to use technical support wisely is part of your technical growth and part
of staying on top. However, the unlimited technical support by phone that we
once took for granted is rapidly disappearing. It is being replaced by limited
technical support transmitted through e-mail and the Web. This means that
increasingly we are expected to get the job done without direct support from
the original equipment manufacturer (OEM). Technical support is out there,
but it must be used wisely to be cost-effective.
Telephone Support
Many telephone-based support systems are geared toward novice and home
users, not to knowledgeable, well-trained technicians, and many try to walk all
callers through basic installation procedures. Exercise patience when talking to
someone at this level, who probably had to complete a basic troubleshooting
procedure required by his or her employer; that person must follow the rules
and procedures of the company. Also, don't be blinded by how much you think
you know. The individual providing phone support just might cover something
that you missed or lead you in another, more fruitful direction. If the problem
remains unresolved, you will usually have to convince support personnel to
send you to the next level of support.
After you get to that next level, always ask the "level 2 technician" to give you
the phone number for the direct technical-support line. Some technicians are
reluctant to give out that number unless the caller promises not to distribute it
and not to call about trivial matters. Every computer technician should build
up a collection of technical-support phone numbers, including as many direct
numbers that bypass the usual voice-mail routing system as possible. The
major drawback to technical-support lines is the amount of time callers often
spend on hold. If you are going to rely on telephone support, it may be
worthwhile to consider priority support for critical incidents. These are feebased hotlines, often with toll-free numbers that provide quicker service—for a
price.
TIP
It is a good idea to have the problem computer in front of you
when you call. Often, you will be asked to follow some basic
instructions while you are on the line with the technician. It is
more believable to the technician to hear you describe the failure
in real time, rather than simply telling the technician that you
have already tried the recommended solution to no avail.
Online Support
Online technical support is becoming a better option. Most free phone support
today is only provided to registered owners for a limited time. If you want
ongoing support, you will have to subscribe to a service or use a pay-as-yougo phone line. Checking vendors' Web sites or online forums on commercial
networks such as MSN often provides a solution without the need to contact
the company. Many forums have libraries of technical support questions that
have been posed about particular products. By searching these libraries, you
can often get immediate answers to your questions. Some sites also have
troubleshooting "wizards" that walk you through a diagnosis and solution to
your problem. If not, post questions and hope for an answer, either from the
OEM or from another user.
Remember, if support is essential to you and your OEM does not provide the
level of service you need, you can always change OEMs (if you work in a large
company, inform your supervisor of the problem). Before taking that step, tell
the OEM you are considering another OEM and explain why. You could also
point out that if the way you've been treated is typical of their service and
support, you will post it as a cautionary tale in a newsgroup or two.
Working Safely
When working with computers, part of the expanded "toolkit kit" is providing a
safe working environment for both humans and the hardware. Computers and
their peripheral devices are electronic equipment, so most safety issues relate
to electrical power. However, when you work on this equipment, there are
several other concerns to take into consideration, as listed in the following
table.
Problem
Prevention
Back
injuries
Some equipment, such as printers, monitors, and even the
computer itself, can weigh several pounds (10–20 pounds or
more for newer, larger monitors). This might not seem like
much; however, improperly picking up (or dropping) the
equipment can result in back or other injuries. Be especially
careful when removing a component from its original
packaging. These components are generally packaged very
tightly to provide protection during transport and can be
difficult to remove.
Cuts
Be very careful when removing covers from computer
components. The frames of the cases are often made of thin
metal with sharp edges. Also, poorly cut or stamped parts
might still have metal burrs, which are very sharp. Devices
such as scanners and monitors have glass components that can
break.
Tripping
Computers tend to have many cables and wires. If not properly
installed, these wires and cables can constitute a serious
tripping hazard. Use cable ties to bundle up cables and reduce
the "spaghetti" effect. Also avoid running cables under carpets
and areas where people walk.
When installing or working on any equipment, make sure that the work done
conforms to all applicable local and national safety codes, such as Occupational
Safety and Health Administration (OSHA) and National Electric Code (NEC)
standards. Many companies have their own internal safety departments and
safety manuals. Be sure that you are familiar with them as well.
Power and Safety
Power is the primary safety hazard encountered when servicing a computer.
Be familiar with the following guidelines when working with electrical devices
and components.
ESD
The primary electrical-power concern when working with computers is ESD.
This subject is covered fully in Chapter 22, "The Basics of Electrical Energy."
Remember that ESD can destroy sensitive computer parts even when the
discharge is imperceptible and harmless to humans. If proper ESD tools are
not available, touching the case (specifically, the power supply) while working
on the computer or its components provides some protection. However, this
only works if the power supply is plugged into a properly grounded electrical
outlet. For a review of power supplies and how to work with them, see Chapter
5 "Power Supplies."
Grounds
When used to refer to electronic equipment, the term ground can be
confusing. Generally speaking, a ground is any point from which electrical
measurements can be made. In most cases, a ground means earth ground.
With early electrical systems, the earth was used as a path for electrical
current to return to its source. This is why telegraphs required only one wire
(the earth ground serves as the other conductor). In most instances, the frame
of the computer is at ground potential or earth ground, as long as the power
cord is installed and connected to a properly grounded system. Some
electronic equipment uses a special path or conductor for its ground. This is
known as signal ground and is not the same as earth ground.
Electronic equipment is both susceptible to and a source of electromagnetic
interference (EMI). A properly grounded computer prevents the transmission
of EMI and protects itself from other sources of EMI. Unchecked, EMI distorts
images on a video display and can corrupt communications equipment and
data on floppy disks.
High Voltages
For the most part, a computer uses ±5 and ±12 volts DC. However, two
devices use much higher voltages: power supplies and monitors. With these
two exceptions, there are generally no electrical hazards inside a computer.
Power Supplies
The power supply uses 120 volts AC. This voltage is found inside the power
supply case. In most cases, there is no need to open the power supply case
and work on the power supply. The cost of a new power supply is low enough
that it is generally easier to replace than repair. However, should you decide
to open the case, be careful. Remember, the power switch on most computers
(usually located on the front of the computer) also uses 110 volts AC to turn
the power supply on or off. If you are working on a computer and leave it
plugged in to provide proper grounding, this could present a hazard.
Monitors
Monitors use very high voltages (30,000 volts) to drive the CRT (cathode-ray
tube). Remember that monitors are dangerous even when unplugged. They
can store this high voltage and discharge it if you touch the wrong parts.
Working inside the monitor case should be left to a properly trained technician
with the necessary tools.
Power Safety Guidelines
The following are some general guidelines to observe when working around
computers:
Never wear jewelry or other metal objects when working on a computer.
These items pose an electrical threat that can cause short circuits, which
can destroy components.
To avoid spills, never use liquids around electrical equipment.
Do not defeat the safety feature of the three-prong power plugs by using
two-prong adapters.
Replace any worn or damaged power cords immediately.
Never allow anything to rest on a power cord.
Avoid using extension cords. These can become tripping hazards. Also,
they may not be rated to carry the current requirements of the system.
Keep all electrical covers intact.
Make sure all vents are clear and have ample free-air space to allow heat
to escape.
Some peripheral devices such as laser printers and scanners use high
voltages. Before removing any covers or working on any of these devices,
be sure to read the manufacturers' manuals carefully.
Fire
Uncontrolled fire is not pleasant to think about, but it is a fact of life. A
workplace fire can be disastrous in terms of both injury to people and lost
equipment. Knowing what to do in the event of a fire can save valuable
equipment and, most important, lives. Here are a few tips to help prevent fire
and protect yourself:
Fire is fast, dark, and deadly. If a fire is detected, and it cannot be
controlled with local resources within 30 seconds, exit at once. Do not
delay at the scene; call the fire department from another location—one
that is safe.
Always know the emergency procedures to be carried out in case of fire at
your workplace.
Know the location of the nearest fire exits.
Know the location of the nearest fire extinguishers and how to use them.
Don't overload electrical outlets.
Simply knowing the location of a fire extinguisher is of no value unless you
know how to use it. If you don't, contact your safety department or local fire
department. They will be glad to help you get the training you need. Also,
remember that using the wrong type of fire extinguisher can be worse than
not using one at all.
There are three basic types of fire extinguishers for nonprofessional use, as
shown in Figure 19.1.
Figure 19.1 Fire extinguisher types
Environmental Issues
Many computers and peripheral devices (especially printers) use consumable
or recyclable components. To help keep our environment safe, you should be
aware of these items and use them properly.
Examples of recyclable items or items that require special disposal are
Batteries
Toner and cartridge kits
Circuit boards
Chemical solvents
Monitors (CRTs)
Be sure to follow the manufacturers' recommendations for recycling or disposal
of any of these items. Some items, such as toner cartridges, even have
prepaid shipping labels so that they can be returned for proper disposal.
When purchasing or using any kind of chemicals (cleaners, for example) that
you are not familiar with the proper use and disposal of, be sure to check the
material safety data sheet (MSDS). This form that describes the nature of any
chemicals manufactured. It includes generic information about the product's
chemical makeup and any recognized hazards (including what to do and who
to call if there is a problem). These forms are required by law, so ask to see
them. Chemical suppliers must provide the purchaser with the MSDS for
products, if requested. Also consider purchasing sprays with a manual pump
dispenser or compressed air rather than chlorofluorocarbons (CFCs) or other
propellants that can be harmful to the environment.
Lesson Summary
The following points summarize the main elements of this lesson:
Having the proper tools and resource materials is critical to being an
effective A+ technician.
A complete toolkit includes a variety of simple hand tools, plus the
software needed to maintain the classes of computers and the operating
systems you will be managing.
It is a good idea to carry spare parts and a laptop as part of your toolkit.
Both can be very useful when repairing a computer with failed
components.
The toolkit can consist of both inside and outside resources. Outside
resources may include online support services, dial-up technical support,
other technicians, and continuing education.
Workplace safety is as important as any other resource.
Don't dally in the event of fire. If it can't be contained quickly, get out
and get help.
3 4
Lesson 2: Planning and Performing Regular
Maintenance
Maintenance is not the same thing as repair. Proper maintenance can prevent
the need for repairs when performed in a timely fashion. At the same time,
performing needed maintenance can sometimes do more harm than good. The
old adage "If it isn't broke, don't fix it" applies just as much to computers as it
does to a tractor. This lesson covers the basics of developing plans and
procedures for performing routine maintenance.
After this lesson, you will be able to
Describe the methods and tools available for planning computer
maintenance
Identify and describe the basic system maintenance required for the
typical desktop PC
Extend the useful life of computer hardware
Avoid major problems caused by unexpected downtime
Estimated lesson time: 35 minutes
Developing a Set of Maintenance Plans and Procedures
Computers are devices built on the very concept of logic. A logical approach
will go a long way toward keeping them running properly. Having a wellorganized, predefined set of plans and procedures covering the different
aspects of computer care for every class of computer and operating system you
deal with is required to make sure that you offer the same level of appropriate
care to all of your clients.
Let's define the terms plan and procedure. A plan is the broader scope of care,
and it can contain several procedures. For example, a periodic maintenance
plan can detail the activities and tasks that should take place at regular
intervals (daily, monthly, annually, and so on), or relative to some specific
activity, like a system upgrade. A procedure is a detailed list of steps that
should be performed, often in the form a checklist. This list can also include
the necessary tools, parts, and remarks about important issues regarding the
procedure.
One way to organize plans and procedures is to have a maintenance policy
manual. These policies can be ordered by time since the last regular
maintenance, and there should be an appropriate plan for each interval. The
monthly plan might include regular disk defragmentation, a performance
inspection, a short conversation with a user to ascertain if the system is
performing as well as expected, and an update of the master recovery disks.
Some of these same procedures might also show up on the semiannual and
annual plans. The plan references the procedures, which are kept in a separate
part of the folder or another folder altogether. If a change in policy or a
change in the operating environment requires changes to a given procedure
(perhaps due to new software), then simply updating a machine with the
procedure will automatically bring all the periodic plans into compliance.
One of the keys to success is to develop a maintenance program that takes
into account the types of computers you will be working on, the needs of the
end user, and the best practices recommendations provided by the
manufacturers of the hardware and the software vendors. Another critical
element of success is putting the plans and procedures into writing and
keeping good records of the tasks performed, as well as the computers on
which they were performed.
Automated Tasks
Windows includes some form of Task Scheduler in the current versions. It can
be set to automate the performance of many common jobs like disk
defragmentation during hours of no or low use.
Keeping Proper Records
When working with computers, it is as important to work smart as it is to work
hard. Being organized and keeping good records is the key to becoming
efficient, effective, and successful. How much time does it take you to check
current configurations when you install a new card on the same computer or
find out what the current version of the operating system is? How long does it
take to restore important files when a user accidentally erases them?
Spending a few minutes reviewing and updating your records each time you
perform routine maintenance or perform an upgrade will save you hours in the
long run.
A simple set of records with essential information and a work history for each
computer you work on can make identifying tasks, settings, and potential
problems much easier. Excel or Access can be used to make virtual quick
references. Keeping it on a laptop makes it both easy to maintain and easy to
access when out on a call. Be sure to back up the data and keep a hard copy
on file for quick reference. The following table provides some suggestions
about the information you might want to keep.
Suggestion
Name each
computer.
Usage
The actual name you choose does not matter, but make it
unique and descriptive. One idea is to use the same name
that Windows uses to identify the computer on a network.
You may have to add some notes about who the related
client is or the location. Establish naming conventions to
make remembering them easier. Use names in addition to
serial numbers.
Include the operating system name and version, startup
and configuration files, hardware IRQs (interrupt requests),
Document
I/O (input/output) base address, direct memory access
all technical (DMA) channels, device driver names, processor type and
information. speed, size of cache, RAM (random access memory), BIOS
(basic input/output system), monitor, video card, modems,
and sound cards.
Save startup
data to
Include the startup disk (based on the current version of
floppy disks
(unique
data).
the operating system), device driver disks, and recovery
disks—as required by an antivirus program or system.
In your log of events for each computer, include such
Keep an
things as the user, application installations (date and
incident log. version), upgrades (hardware), and problems (cause of
failure and actions taken for resolution).
Set up a
local and
Include in the front part of the log a list of the tasks that
specific
are to be performed and how often. Note the dates when
maintenance
they have been performed and by whom.
task
schedule.
Basic Hardware Maintenance
Cleaning
For the most part, computer equipment is very reliable and lasts a long time.
However, dirt and other airborne contaminants will greatly accelerate the
deterioration of computer equipment. Therefore, part of a good preventive
maintenance regimen is keeping the equipment clean.
The first step is to be sure that the computer is installed in a computer-friendly
environment. This means that it should be in a dust-free (relatively speaking),
smoke-free, and humidity-controlled (within a range of 50–70 percent relative
humidity) location. Generally, a normal office environment will qualify as
computer-friendly. However, a normal office environment is not the only place
that we find computers. Many computers are located on a warehouse floor, in
a shop, or grouped together with large, industrial equipment.
In the event that the location of a computer is not as desirable as it should be,
the frequency of preventive maintenance (cleaning) should be accelerated. In
these instances, consideration should be given to establishing a computerfriendly zone around the computer, for instance, installing it into a cabinet and
providing a source of clean fresh air. The following table describes what a
computer technician should include in a basic cleaning kit.
Item
Usage
Lint-free
chamois
cloth or
old t-shirt
A cloth is useful for cleaning the outside surfaces.
Cleaning
solution
Standard household cleaning solutions (not extra-strength)
can be used in moderation. The solution should be applied to
a lint-free cloth and then applied to the computer surface. Do
not use aerosol sprays. These generally use solvents as a
propellant, which can dammage the plastic as well as the
electrical components of a computer.
Foam
swabs
Use these with cleaning solutions to clean small parts such as
the wheels inside a mouse. (Cotton swabs are not
recommended, because the cotton fibers can come off and be
a contaminant themselves.)
An antistatic spray or solution should follow any cleaning in
Antistatic
spray
envi- ronments with a risk of ESD. A solution composed of 10
parts water to 1 part common household fabric softener will
do.
Small
paintbrush
Use to remove dust from around the computer and inside its
or small
cabinet. The vacuum can be used to remove dust from the
hand-held
keyboard and other input devices.
vacuum
cleaner
Canned
air
Use to remove dust from the power supply fan or from inside
a computer. These cans can be purchased from any computer
supplier; they are made especially for removing dust from
electronic equipment.
CAUTION
Never use liquids to clean inside a computer. Never apply liquids
directly to the surface of a computer. Never use solvent-based
cleanser or aerosols.
The proper placement or location of a computer relative to its environment is
important for ease of maintenance and long life. In summary, a computer
should be
Located in a dust-free and smoke-free environment
Subjected to controlled humidity (50–70 percent relative humidity)
Subjected to controlled temperature (do not place too close to a heater or
in direct sunlight—avoid temperature extremes)
Have good ventilation (make sure fan and ventilation vents aren't
blocked)
General Preventive Maintenance
For the most part, the MTBF (mean time between failures) of a computer and
its peripheral devices is quite long. By following the general cleaning and
safety measures just described, you can extend this time. This section
describes several components and their special maintenance requirements.
Monitors
Monitors require very little maintenance. To keep a monitor in peak condition,
use the following guidelines:
Keep it clean—use periodic cleaning, dusting, and good common sense
with a monitor.
Use simple cleaning solutions, not aerosol sprays, solvents, or commercial
cleansers. Don't use window-cleaning sprays on a monitor screen.
Do not leave unattended monitors on for extended periods of time. Use a
screen saver or the computer's power-conservation features to reduce
power consumption and (on older models) to prevent burn-in of the
monitor screen.
Don't ever attempt to work inside the cabinet unless you are properly
trained to do so.
Don't tamper with the monitor. Monitors emit x-ray radiation. Changing
the settings or operating the monitor with the cover removed can disable
the manufacturer's safety devices, thus increasing the hazard.
Hard Disk Drives
Hard disk drives are another type of device that requires very little
intervention to keep running. Mechanical failure of hard drives is rare, and,
when it does occur, the solution is generally replacement. We cover operatingsystem-related maintenance issues in the next lesson. Here are a few
suggestions for preventing mechanical problems with hard drives:
Avoid rough handling.
Never move a hard disk when it is still spinning.
Never expose the internal housing to open air.
Perform regular data backups and disk maintenance tasks.
Floppy Disk Drives
Floppy disk drives are highly susceptible to failure. This is due mostly to the
fact that they are exposed to the environment (through the disk slot) and to
mechanical damage from insertion and removal of disks. When they fail, the
best solution is usually to replace them because they are inexpensive and
simple to install. Here are a few tips to increase the life of floppy drives and
disks:
Do not expose the disks to magnets.
Never touch the exposed surface of a floppy disk.
Do not allow smoking near a computer.
Clean the read/write heads. Special head-cleaning diskettes and solutions
such as isopropyl alcohol and methanol that do not leave a residue when
they dry are available. Cotton swabs are not recommended because of the
fibers they shed. Use cellular foam swabs or a lint-free cloth.
Keyboards and Pointing Devices
Keeping a keyboard and mouse clean is the key to prolonging their lives.
Never place drinks (coffee, soda, tea, and so on) around a keyboard; spilling
liquids is a common cause of keyboard failures. Here are a few tips to increase
the life of a keyboard, mouse, or other pointing device:
Use a handheld vacuum cleaner to remove dust from the small crevices.
Never use spray cleaners.
Clean a mouse or trackball by removing the ball and cleaning the rollers
(if it has a ball inside).
When using a light pen, never touch the ends with your finger.
Printers
Printers are more mechanical than other peripherals and therefore require
more attention. Because they use paper, ink, or carbon, printers generate
pollutants that can build up and cause problems. Always check the
manufacturer's recommendations for cleaning. Following are a few steps for
cleaning the most popular types of printers.
Dot-Matrix Printers
Adjust the print-head spacing.
Check the tension on the print-head positioning belt. Use a nonfibrous
swab dipped in alcohol to clean the print head.
Clean the printer's roller surfaces.
Clean the surface of the platen.
Clean the gear train of the paper-handling motor.
Apply light oil to the gears using a foam swab.
Turn the platen to distribute the oil.
Apply a light coating of oil to the rails.
Move the carriage assembly to distribute the oil.
Ink-Jet Printers
Adjust the print-head spacing.
Check the tension on the print-head positioning belt.
Clean the printer and its mechanism.
Clean the printer's roller surfaces.
Clean the surface of the platen.
Clean the surface of the ink-jet print head.
Clean the gear train of the paper-handling motor.
Apply light oil to the gears using a foam swab.
Turn the platen to distribute the oil.
Apply a light coating of oil to the rails.
Move the carriage assembly to distribute the oil.
Laser Printers
Vacuum to remove dust buildup and excess toner from the interior.
Remove the toner cartridge before vacuuming.
Clean the laser printer's rollers using a damp cloth or denatured alcohol.
Clean the gear train of the paper-handling motor using a foam swab.
Apply light oil to the gears using a foam swab.
Distribute the oil throughout the gear train.
Clean the writing mechanism thoroughly using compressed air. If
possible, wipe the laser lens with lint-free wipes to remove fingerprints
and stains.
Clean the corona wires using a foam swab dipped in alcohol. Be careful
not to break any of the strands because, if you do, your printer will be
rendered useless until they are repaired.
Preventive Maintenance Schedule
There are no universal preventive maintenance schedules that work on every
computer. Each schedule must be individualized to meet the needs of the work
environment. Use the following suggestions as maintenance guidelines for
developing your own polices and procedures.
Do This Daily
Back up data.
Check computer ventilation to ensure that it is clear. Remove any paper,
books, or boxes that might impede the flow of air into or out of the
computer.
Do This Weekly
Clean the outside of the case.
Clean the screen.
Run the appropriate disk inspection program for the operating system in
use on all hard disks. Windows comes with scheduling programs to help
you accomplish this on a regular basis. Information on these procedures
is contained in Lesson 3.
Run a current antivirus program and check all drives. These programs
also come with scheduling features to help you accomplish this on a
regular basis. They also remind you when to update the virus list (usually
done through the manufacturer's Web site).
Inspect all peripheral devices.
Do This Every Time a New Device or Software Application Is
Added to the System
Back up all critical data and system files.
Update the ERD, Rescue disk, or other core files to a floppy in case of
system failure or corruption.
Store the user license, configuration data, any special settings, and
technical support access information in the permanent record file kept for
this computer.
Complete and submit the warranty registration card for this product.
Do This Monthly
Clean the inside of the system.
Clean the inside of any printers.
Vacuum the keyboard.
Clean the mouse ball and tracking wheels.
Defragment all hard disk drives.
Delete any unnecessary temporary files.
Do This Every Six Months
Perform an extensive preventive maintenance check.
Apply an antistatic solution to the entire computer.
Check and reseat all cables.
Run the printer's self-test programs.
Do This Annually
Reformat the hard disk drive and reinstall all software. Don't forget to
back up data first.
Check all floppy disk drives.
Consider an upgrade to your computer. Check to see that your
components can handle your workload.
Lesson Summary
The following points summarize the main elements of this lesson:
The modern microcomputer is very reliable, but still requires regular care.
Regular preventive maintenance can reduce the need for repairs.
Part of preventive maintenance is keeping a computer clean.
Never use solvent-based cleaners on a computer.
Never use liquids on the electrical components inside a computer.
Create and implement a regular maintenance plan for each computer
under your care.
3 4
Lesson 3: Maintaining the Windows System
Environment
This lesson describes the basic steps required to provide proper periodic
maintenance to the operating system and data files contained on a Windowsbased computer.
After this lesson, you will be able to
Describe the methods and tools available for performing Windows
maintenance
Identify and describe the basic regular maintenance steps required to
maintain the Windows file system
Inspect, clean up, defragment, and back up data on both Windows 98 and
Windows 2000-based computers
Estimated lesson time: 45 minutes
It's not just the outside of a computer that needs to be cleaned; regular
housekeeping of the operating system and hard disks is critical to safe, robust
performance. The data on the hard disks also requires periodic maintenance
and tidying up. The Windows environment is constantly undergoing change.
Every time a file is created, opened, or closed, and every time a new software
application or hardware device is added, the content of the file system, and
often the nature of the Registry, is changed. Over time, the underlying
organization of files on the machine becomes fragmented. This fragmentation
reduces system performance because the system must work harder to
assemble the files so that they may be used.
Numerous temporary files are also created on the system on a regular basis.
These are not always removed as often as they should be and they can clutter
the storage system. If a disk used for virtual memory paging gets too full,
scratch file size is reduced and overall system performance degrades. User
data, along with system files, must be backed up on a regular basis to prevent
loss in the event critical files become corrupted or the hard disk fails.
Over time, the magnetic media's format weakens. It must be inspected and
refreshed before the aging results in data loss or system failure.
Early versions of Windows lacked robust support for managing these tasks, but
that has changed. Both Windows 98 and Windows 2000 offer a variety of tools
that can do the job. There is one other preventative maintenance task for
which you might want to consider a third-party solution: virus detection and
elimination. With the widespread use of the Internet and e-mail, a computer
virus can spread faster than the flu. They are also difficult to detect as idle,
malicious minds seem to keep finding new routes of infection.
Periodically, Microsoft offers updates to the code for its operating systems, and
many vendors offer periodic patches to their software as well. Some of these
updates fix specific problems, whereas others are designed for use on virtually
every computer running the operating system or program. This type of file
update does not necessarily occur at regular intervals, but it is a good idea to
regularly check for appropriate updates. When a worthy upgrade is released, it
should be deployed on all computers that would benefit from it.
With these topics in mind, we can identify several things that should be done
on a regular basis to keep the Windows operating and file systems secure and
running at peak performance, and designate an order in which to perform
them:
Provide an appropriate level of virus protection.
Remove old and unused files on a regular basis and keep adequate open
space on disks used for virtual memory.
Scan the media for errors and fix any problems.
Defragment the drives.
Back up files and keep updated recovery disks.
Periodically check for updates, and apply them as appropriate.
Virus Protection
Viruses are nasty little programs that can wreak havoc on a computer and its
data. The sole purpose of a virus is to replicate itself and make life miserable
for computer users. Many viruses are simple annoyances, but some of them
can cause irreparable harm to files. Viruses can be caught from various
sources including shareware, files downloaded from the Internet, software
from unknown origins, and bulletin boards.
There are several different types of viruses:
File infectors attach themselves to executable files and spread to other
files when the program is run.
Boot sector viruses replace or hide inside the master boot record (or boot
sector on a floppy disk). They write themselves into memory any time the
computer is booted.
Trojan horses are disguised as legitimate programs, but, when loaded,
they begin to harm the system.
Macro viruses attach themselves as executable code inside a document
(such as a Microsoft Word document) and run when the document is
opened. (They can also attach themselves to certain kinds of e-mail.) It
used to be true that you couldn't get a virus from opening a document;
running a program was required. Unfortunately, this has changed thanks
to the widespread use of macros by computer users. Although macros are
very valuable, they mean that when you open a document you are
running a program.
Polymorphic viruses are an especially unsettling class of invader. They're
designed to modify themselves over time and replicate new forms. This
makes them both unpredictable and harder to detect.
There is no sure defense against viruses, and the whole software industry has
devoted great effort over the last few years to designing detection and
remedial software. These programs can be purchased and downloaded from the
Internet or obtained through regular distribution channels. Because viruses
change rapidly and new ones appear almost daily, it is best to shop for an
antivirus utility that comes with free or low-cost regular upgrades that are
easy to apply. The following are some general guidelines for virus programs:
Make sure your choice is compatible with the specific version of Windows
on the system, including any upgrades. The wrong antivirus program
might do more damage than good.
If the computer has a BIOS setting that allows you to disable boot-sector
writes (prevent applications from writing to the boot sector of the hard
disk), consider enabling it. This setting must be disabled before installing
Windows updates and some other programs as well. Keep in mind these
BIOS-level virus checkers are very limited in ability and should not be
relied on for total protection.
Viruses are often transmitted by floppy disks. Be careful when reading a
floppy disk of unknown origin or using your disk on an unfamiliar
machine.
Currently, many viruses and macro viruses are transmitted over the
Internet. Use extreme caution when you download files, especially if they
come from sources other than a manufacturer's Web site. The most
secure protection against Internet-distributed viruses is to have an
antivirus program running at all times (or at least when you're
downloading and first running new files).
Trust no one when it comes to loading programs on your machine. Be
aware that any program you load on your computer could contain a virus.
Be sure to keep your antivirus program updated. Hundreds of new viruses
are written and transmitted each month.
When designing an antivirus program, you need to take into consideration the
needs of the user and the level of risk. A computer that does not have a
connection to the Internet or a LAN (local area network) and rarely receives
files from outside sources is at little risk. A file server that gets files from a
variety of sources, some downloaded from outside, should be equipped with
very robust virus detection. In the latter case, it's good if the software has the
capability to alert a system administrator with an e-mail message or page
when a virus is detected.
Disk Cleanup
Cleaning up old files not only saves on media and reduces copy time during
backups; it also frees up disk space and improves file system performance.
Both Windows 98 and Windows 2000 offer Disk Cleanup wizards available on
the System Tools menu that make cleaning up old files on a disk easy. Simply
invoke the routine and direct it to the desired drive. Wait for the utility to
prepare a list of various temporary files, unnecessary program files, files that
have been moved to the Recycle Bin, and Internet files that are cached locally
on the disk. You can then determine which of these files you wish to delete.
Simply click OK and the files are removed. Figure 19.2 shows the wizard ready
to delete the files.
Figure 19.2 The Disk Cleanup Wizard operating in Windows 2000 Professional
Checking Drive Integrity with ScanDisk
ScanDisk is an incredibly useful program, and, in the early days of MS-DOS,
many people bought utilities like this to keep their system running properly. It
inspects the file system and fixes problems and can do so when the system is
in use. ScanDisk is built into all the currently shipping versions of Windows.
You should be very careful to make sure that any version of ScanDisk you use
is actually the one that is compatible with the version of Windows and the file
for the PC to be checked and corrected. On most systems, ScanDisk is
available in both a command-line version and one that operates within the
Windows graphical user interface (GUI).
The ScanDisk utility can both detect and fix problems on local hard disks,
floppy drives, RAM drives, and some memory cards. It works with compressed
drives set up using DoubleSpace and DriveSpace, but offers only limited
support for third-party compression software. Among the operations you can
perform on a ScanDisk are
Inspecting the physical surface of the drive for bad sectors
Inspecting the file structure, compression structure, and volume
signatures of any compressed drives
Locating and repairing crossed-linked files and lost clusters
Verifying the integrity of both FAT16 and FAT32 file systems
Verifying and repairing problems with the directory tree structure of a
drive
ScanDisk operates in two modes: standard and thorough. Standard performs a
check of both files and folders; the thorough mode adds an inspection of
integrity of the drive's physical surface. You can set ScanDisk to run
automatically and fix errors or to prompt you before making any corrections
(see Figure 19.3).
Figure 19.3 ScanDisk in action.
Windows 2000 has a similar tool that is accessed in the Properties dialog box
for a disk. Open the Tools tab and select the Error-Checking option. Click OK
to start the program if the disk is not shared and in use. If it is, the program is
automatically run the next time the computer is started.
Keeping Files Orderly with Disk Defragmenter
An operating system as complex as Microsoft Windows constantly opens and
closes files, as do applications and users. Due to design issues, the file systems
do not necessarily place data on storage media as a single block when they
write a file to disk. As a result, over time, the files on the drive can become
severely fragmented (spread out across different sectors of the hard drive).
This fragmentation can seriously degrade system performance, as each time a
file is opened it must be gathered from several places and stored in memory.
Disk Defragmenter is a utility you access by clicking
Start\Programs\Accessories\ System Tools\, and it is found in all current
versions of Microsoft Windows. It can be used to analyze a disk and see just
how badly fragmented the files are, and then it can rearrange the disk, placing
the files in contiguous blocks. The newest versions of Disk Defragmenter have
logic that makes them aware of the way the operating system reads
executable and dynamic-link library (DLL) files, so they can place clusters in
the order they are read. Both of these operations can significantly improve
system performance. This utility should be run at least monthly, and more
often on busy systems. Any time a computer user complains of a slowdown
over regular system performance, fragmentation analysis should be
performed. Figure 19.4 shows the Windows 2000 version of the program in
operation. As you can see, it works with both NTFS (Windows NT file system)
and file allocation table (FAT)-based file systems.
Figure 19.4 Disk defragmentation in process.
You can schedule the defragmentation to take place when the computer is not
being used, so the speed of its operation is generally not a concern. Some
screen savers or other programs that involve disk activity can slow down the
operation of the defragmenter, so for best performance they should be
disabled during its operation. Windows offers a Maintenance Wizard to
automate this and other common disk care tasks.
File Backups
Hard drives fail. Critical files become corrupted. Data loss is not a matter of if,
but when. As a computer professional, one of the most valuable services you
can perform is ensuring that your client's critical data is secure. The best way
to do that is by developing a good backup plan and making it as automatic as
possible. In the days of MS-DOS and in the early days of Windows, Microsoft
provided a floppy disk-based backup utility. It was cumbersome to use, and
floppy disks were unreliable. Creating a backup volume that spanned from 10
to 20 disks was asking for trouble.
Today, Windows comes with built-in backup software that supports a variety of
media. You can back up to tape, another hard drive, or removable media.
Third-party vendors provide additional backup software that can write to CD-R
(CD-recordable), CD-RW (CD-rewritable), and other forms of inexpensive,
high- volume media. Given that today's hard drives provide multigigabyte
storage, advanced backup strategies have to be simple and effective.
Developing a Backup Plan
There are generally accepted practices and common methods used for data
backup, and both Windows 98 and Windows 2000 ship with integrated backup
software. Tailoring a backup plan that works for individual needs based on this
software is a simple process, but must take into consideration the amount of
data to be backed up, the frequency of backup, and the equipment available.
The various Windows file systems provide an attribute that can be attached to
a file to indicate when it was backed up. This can be used to filter which files
are copied based on the last time they were backed up or if they have been
backed up at all.
There are five different common types of backups based on frequency and
which files are added to the archive. With some versions of software, you must
select the files manually, whereas in others a wizard or a predefined file list
determines what data is moved to the archive. The backup types are
Normal backup. Copies specifically selected files to the archive, no
matter when the files were last backed up or if they have been modified.
You can choose individual files or entire drives and directories. When
instituting a backup plan, the first step should be to create a normal copy
of every important file. As each file is copied, it is marked as having been
backed up.
Straight copy backup. Similar to normal backup, copies all selected
files, whether they've been backed up recently or not. The difference is
that it does not mark the file as having been backed up. This is useful if
you are making a separate backup copy of a set of files, because it will
not exclude them from the next regular backup.
Daily backup. Copies all the preselected files modified on the date the
backup was performed. The files are not marked as being copied to the
archive.
Incremental backup. Copies just the files that have been created or
modified since the last regular backup. This process changes the archives
setting on the file when it is copied. Incremental backup is used in
combination with normal backup. If it is necessary to restore a drive, the
last normal backup is placed back on the volume, followed by the contents
of the most recent differential backup.
Differential backup. Archives only those files that do not show that they
have been backed up since the last normal or incremental backup.
A backup plan incorporates these different backup methods into a series of
regular copies of data that produces an archive refreshed frequently enough to
meet the user's needs. In some cases, backups must be very frequent and
complete because core data is constantly changing. In other cases, most of the
files hardly change at all, so infrequent differential copies may work.
The amount of data and the backup frequency will also dictate the type of
hardware to be used. Inexpensive external storage devices like a Zip drive
work fine for low-volume applications. For high-volume, high-speed archiving,
one or more high-speed SCSI (Small Computer System Interface) tape drives
or an equally expensive redundant array of independent disks (RAID) may be
employed.
NOTE
Be sure both the device and the media are compatible with the
operating system, file system, and backup software that will be
used on the system.
Many companies use a rolling backup plan, which provides a full normal
backup of the entire contents of system drives at regular intervals, with
incremental or differential backups occurring between those archiving backups.
There is a wide variety of media used for backups. These include various tape
formats, optical discs, and hard drives. Magnetic media is notably unreliable.
As insurance, many people rotate a series of tapes to be used for a given
backup. For example, if backups are done on Monday, Wednesday, and Friday,
then a different set of tapes might be used for each day.
Backup Plan Gotchas
Backup plans are a form of system security, and it is wise to prepare for the
unexpected. There are a few things to consider when setting up policies:
Make sure that your backup copies are stored in a safe, environmentally
sound location. It is generally wise to keep a second set off site in the
event of fire or other disaster.
Keep the copies in a secure location. Sensitive data can be stolen from a
copy almost as easily as from the computer itself.
Backups are sometimes your last line of defense against a virus attack.
Because some types of viruses can reside on a system for a long time
before being detected, it is a good idea to keep one or more long-term
backups (from the preceding month or so) available in the case infection
and data loss.
Most backup software is unable to copy files that are currently open and
may be trained to skip certain files unless given specific instructions. Be
sure the plan includes a method that allows all targeted files to be copied.
Backup technology changes over time, and so does compatibility. When
upgrading hardware, software, or the operating system, be sure that the
new components and the old components will work together and allow the
restoration of backed up data when needed.
Backing Up Files with the Bundled Windows Backup
Applications
The Windows 98 and Windows 2000 operating systems ship with bundled
backup software that is located under System Tools. In Windows 98, you must
add it, as it is not automatically installed as part of the regular setup. The
features and hardware supported vary from platform to platform. Most offer
the ability to predefine jobs, which are collections of files, or drives, that are
targeted for backup. This allows you to designate groups of files, which can
then be backed up at regular intervals. Most also support the various backup
types mentioned earlier. For more information on just which hardware
products are supported as backup devices, how to use the program, and the
specific feature sets included in a given version of Windows Backup, refer to
your operating system help file and related documentation. Figure 19.5 shows
the Windows 2000 Backup program at work.
Figure 19.5 The Windows 2000 Backup utility in action in the backup
NOTE
There is a fundamental difference between the Windows 2000
Backup tool and the ones for other versions of Windows (including
Windows NT). Windows 2000 organizes backup media in pools
managed by the removable storage service. This means you must
use a specific piece of media for a given backup job. If you have a
weekly backup that is supposed to run every Wednesday, then the
machine looks for the media that is attached to that job. If you put
in the tape that is supposed to be for the Friday job, it generates
an error and the job does not run.
Backing Up the Registry and Core System Files
One of the most important parts of the system backup is the system Registry.
As you learned in the preceding chapter, Windows 95, Windows 98, Windows
Me, and Windows 2000 use the Registry to store critical configuration data.
Any time you need to edit the Registry, either by adding a new piece of
software or hardware, or by using a program like REGEDT32, you should
create a full backup of critical system files. These procedures are not the same
for Windows 98 and Windows 2000. Both what is backed up and how it is
backed up is different.
Backing Up the Windows 2000 System State Data
In Windows 2000, any time you perform a backup and check the System State
option in the Backup Tab, the Registry is backed up automatically. Windows
2000 actually considers more than just the Registry as part of its core file
suite, because Windows 2000 needs more than just the Registry data to
restore an operating system to the same state as it was at a given point in
time. The full set of files is referred to collectively as the system state data,
which includes:
The boot files that we discussed in Chapter 16, "Operating System
Fundamentals," under system startup, including various system files and
any other files protected by the Windows File Protection (WFP) system.
Any files contained in the %system root%\System 32\
CatRoot\F750E6C3-38EE-11D1-85E5-00C04FC295EE.
The entire contents of the Registry.
The database that contains all the registration information for the
Component Services Class portion of the kernel.
Information maintained by the system on the Performance Counter
Configuration.
You can also use the Backup Wizard to save the system state data; it offers
you the option during its queries. Keep in mind that you must be logged on
with administrator privileges or be a member of the backup operators' group to
have access to the Backup tool or the Backup Wizard. With the proper
permissions, you can back up data files on remote computers over a network,
but you can only back up system state data on a local machine.
Whenever you save data with the Backup tool, it is a good idea to have it
verify the files (automatically compare the new copy with the original) and to
visually inspect the report that it generates by clicking Export. The report is
displayed in Notepad, and you can print a copy of the report as a record of the
backup. Here is an example portion of such a report:
Backup Status
Operation: Backup
Active backup destination: 4mm DDS
Media name: "Media created 01-Jan-01 at 6:34 PM"
Backup
Backup
Backup
Backup
of "C: "
set #1 on media #1
description: "Set created 01-Jan-01 at 6:35 PM full normal"
Type: Normal
Backup started on 01-Jan-01 at 6:39 PM.
Backup completed on 01-Jan-01 at 6:58 PM.
Directories: 601
Files: 4833
Bytes: 1,308,086,464
Time: 18 minutes and 30 seconds
Media name: "Media created 01-Jan-01 at 6:34 PM"
The bold and italicized text in this example points out three reasons for
keeping a copy of the backup report. It provides a record showing the media
name for a given backup, so you can quickly locate it in your archive to
restore files. It shows that date and type of backup, which can both be used to
verify that a scheduled activity took place. It also shows the amount of space
used on the media, which is handy for calculating how much space remains on
the tape.
Verifying and Backing Up the Windows 98 Registry
Windows 98 also offers a utility for backing up the registry, built into a
program called the Registry Checker. This is a command-line application. Once
again, we see that Windows likes to hide Registry-related tools from the casual
user—you have to know exactly where and how to find it.
Just as with Windows 2000, it's a good idea to do a backup of the Registry
before performing any operation (like installing a new application or piece of
hardware). Windows 98 includes a backup utility within a tool that lets you
examine the Registry and make sure that it is in proper condition.
To run the Registry checker, open a command-line prompt and run the
Start\Run Menu, and type SCANREGW.EXE in the Run dialog box. The
program first scans the contents of the Registry and makes sure that the files
are sound. If everything checks out, it offers to back up the Registry. This
makes the program copy the Registry files and store them in a .cab (Windows
cabinet) file in the \Windows\Sysbckup directory.
Every time you run the program, it creates a new cabinet. The filenames end
in a number, and the most recent version has the highest number just before
the .cab extension. Of course, there are more system files than just the
Registry to be concerned about, and that leads us to another tool.
Checking Critical Files with the Windows System File Checker
System files can be corrupted for a variety of reasons, including improper
system shutdown, problems with disk media, or a new application improperly
overwriting a necessary driver with its version. To minimize both problems and
risks associated with this behavior, the Microsoft developers included a
combination "guardian angel" and administrator utility.
The WFP system tracks all changes to system files and makes sure that any
new files assigned to replace a protected file are valid. It also sends a message
to the system administrator when an improper file replacement of one of these
protected files is attempted.
There are times you may wish to examine the status of these core system files
yourself; for example, if Windows is getting error messages that a certain file
is a problem, or some system service starts behaving improperly. The WFP
system includes the System File Checker (SFC) utility in both Windows 98 and
Windows 2000, which can be run at the command prompt to verify manually
the versions of all system files under protection and reload saved copies from a
hidden cache.
You can use the SFC to verify the integrity of your system files. Open the SFC,
choose Scan For Altered Liles, and click Start. The program reports any files
that do not match the SFC DEFAULT.SFC file. If you know a specific system file
shown on the list is corrupt or missing or you expect it is the cause of some
problem, you can extract it from the Windows installation disk using the SFC
Extract option. In SFC, choose Extract One File From Installation Disk, enter
the full filename when prompted, and click Start. Then give the program the
location of the disk with the file and where you want it to be copied. When you
click OK, the SFC extracts the file to the desired location. The SFC options are
shown in the table below.
SFC
Option
Function
Update the file data in DEFAULT.SFC. Choose this option
Update The when you have updated a system file without running the
Verification SFC and are certain that you want to update DEFAULT.SFC
information to use the updated information about the file the next time
the SFC is run.
Restore
Specify the source location of the file to restore and where
to save the new copy of the file. You are also prompted to
File
Ignore
back up the existing file to the \Windows\Helpdesk\SFC
folder. Choose to back up the file in case there are problems
using the new file.
Skip the file. The next time the SFC is run, this file will
cause the File Changed dialog box to appear because it was
not added to DEFAULT.SFC and it was not restored.
Creating Emergency Repair and Startup Disks
Every Windows computer should have either a Startup disk (Windows 95 or
Windows 98) or an ERD (Windows 2000 and Windows NT) nearby. The
Windows 95 or Windows 98 Startup disk is the same for all computers using
that version of the operating system. In other words, you can use the Windows
98 Startup disk for all Windows 98 computers. You can use Windows 98's
Startup disk to start a Windows 95 or even a Windows 2000 or Windows NT
machine. As long as the file system is compatible, you'll also be able to view
and work with files on the computer. You should use the utilities on a disk for
only that specific version of Windows with which the system Startup disk was
created.
During setup, Windows 95 and Windows 98 offer the option of creating a
startup disk. You can also create one at any time by opening up the Control
Panel, choosing Add/Remove Programs, and clicking the create Start Up Disk
tab. You will need a copy of the distribution CD for that version of Windows
and one blank, formatted, floppy disk.
The Windows 2000 and Windows NT ERD is a different matter. These disks are
specific for the computer on which they were created. The ERD contains three
files: AUTOEXEC.NT, CONFIG.NT, and SETUP.LOG. These are copies of the files
with the same name that are contained in the %SystemRoot%\ Repair folder.
The first two files are used to initialize the MS-DOS environment, and the third
is used by the Windows 2000/NT emergency repair process.
The ERD should be updated any time a change is made to the structure of the
operating system (new drivers, service pack, and so on), or when new
hardware is added to the computer.
Windows 2000 has a wizard available to creating your ERD. It is located in
Programs\Accessories\System Tools\Backup. Under Windows NT, you must
launch the RDISK.EXE program located in the Windows NT directory by clicking
Start/Run and entering the command in the Run dialog box. You will need one
blank formatted 3.5-inch floppy disk.
The ERD should not be used to repair Registry problems. We cover that
process in the next chapter. It should be used if the system becomes so
corrupted that you must restore the original Registry created during startup to
gain access to the system.
Lesson Summary
The following points summarize the main elements of this lesson:
Several routine tasks should be done on a regular basis to keep a
Windows-based computer operating securely at peak performance.
Provide an appropriate level of virus protection.
Remove old and unused files on a regular basis and keep adequate open
space on disks used for virtual memory.
Scan the media for errors and fix any problems.
Defragment the drives.
Back up files and keep recovery disks up to date.
Periodically check for operating system and driver updates and apply
them as appropriate.
How often these tasks should be performed will vary, based on the user,
how the system is used, and the operating environment.
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Chapter Summary
The following points summarize the key concepts in this chapter:
The Right Tools for the Job
The tools needed for computer care and repair are quite simple hand
tools.
Your toolkit should include a collection of startup disks and other software
needed for the types of machines generally worked on.
Accurate information is a critical component of a technician's resources.
Ongoing education is essential.
Creating a safe working environment is part of the job to protect both you
and the equipment.
Planning can save time and ensure that proper care is provided.
Documentation tracks work and make follow-ups more effective.
Planning and Performing Regular Maintenance
Each class of hardware has its own maintenance tasks and procedures.
Viruses are a risk to all computers.
Backups of data must be done in a systematic way on a regular basis.
The hard drive should be cleaned of old files to improve performance and
avoid clutter.
Regular testing and repair of the file system, as well as defragmenting
disks, can improve performance and avoid downtime.
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Review
The following questions are intended to reinforce key information presented in
this chapter. If you are unable to answer a question, review the appropriate
lesson and then try the question again. Answers to the questions can be found
in Appendix A, "Questions and Answers."
1. Name three reasons for adding a laptop computer to your toolkit.
2. What type of solvent should be used to clean the monitor screen?
3. What is a polymorphic virus?
4. What is the ScanDisk program? What is it used for?
5. What is an ERD?
6. What is the best way to remove old, unused files from a Windows-based
computer?
7. How does file fragmentation degrade system performance?
8. Define an incremental backup.
9. Explain the difference between a normal and a copy type of backup.
10. Why is it useful to keep long-term archival files, even if you're making
regular periodic backups on a short-term basis?
Answers
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Chapter 20
Upgrading a Computer
About This Chapter
Computer upgrades are among the most common tasks performed by a
computer technician. With new technology being introduced every day, it is a
constant struggle to stay up to date. Before you can upgrade or repair a
computer, you must know how to take it apart. A thorough understanding of
how to disassemble a computer and put it back together is required of any
computer professional. This chapter provides guidelines for successfully
disassembling, reassembling, and upgrading a computer.
Before You Begin
Before starting this chapter, you should review the previous chapters that
cover the physical components of a computer. Also, if you are not already
familiar with the risks and issues concerning electrostatic discharge (ESD),
review Lesson 2, "Electrostatic Discharge," in Chapter 22, "The Basics of
Electrical Energy."
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Lesson 1: Computer Disassembly and Reassembly
In this lesson, we look at the tools and practices required by a computer
technician to physically take apart a computer and successfully put it back
together.
After this lesson, you will be able to
Develop a systematic and logical approach to repairing a computer
Identify procedures for working on a computer
Identify basic procedures for adding and removing computer components
Estimated lesson time: 20 minutes
Preparation
Knowledge and preparation are the primary ingredients for a successful,
efficient, and profitable upgrade or repair. Before attempting any work on a
computer, it is wise to know what you are working with, and you should have
a good understanding of the problem or task at hand. A few minutes of
preparation can save hours of endless guessing and frustration.
Documentation is one key to preparation. If adequate documentation is not
readily available, your first step is to collect or create it. The Internet is a
valuable tool. Make it a habit to check vendor Web sites for updated drivers
and information before performing any upgrades or repairs. While there, be
sure to download the latest drivers for any new components to be installed.
When you finish a job, don't forget to save the documentation, including an
account of what you did and any problems you encountered.
Documentation to Collect Before Starting the Job
The following list provides examples of the types of documentation you should
assemble before you begin a repair:
A computer configuration sheet listing the devices already on the
machine, hardware settings (IRQ [interrupt request], ports, and so on),
the network configuration, and required passwords for the operating
system.
Copies of the computer and motherboard documentation.
A list of all installed expansion cards. If possible, include the date on
which they were originally installed.
Copies of the operating system documentation (especially if you are not
familiar with the system).
A plan of action. Writing down a checklist of tasks and related tools and
parts before starting a project can help you keep focused and on target.
Remember, plans can always change; but, without a plan, you could find
yourself wandering aimlessly through the project and perhaps getting
sidetracked or lost.
Questions to Ask Yourself Before Starting the Job
Carefully consider the following questions before you open the case of any
computer:
Is this the right computer?
Why am I taking it apart?
Do I have everything necessary to do the job?
Do I need more information before starting this job?
Are there any proprietary hardware components in this machine? If so, do
I have the right tools, parts, and drivers to complete the job?
Do any of these tasks require the assistance of a third-party technician—
for example, internal monitor adjustments?
Tools and Components
Standard Toolkit
You should have a standard toolkit, as described in Chapter 19, "Maintaining
the Modern Computer." Most upgrades (unlike some repairs) require very little
in the way of tools, most just a simple screwdriver. The toolkit should also
contain a DOS—or better yet, the startup disk for your version of Windows to
use if you need to boot the system into a DOS command prompt or edit basic
configuration files.
Items Identified During Planning
Assemble the tools and components identified in the planning stage. If the
update is a major one, make sure you have properly backed up any user data,
as well as the system files and Registry, to be prepared in the event of a
serious problem.
Operating System Disk
Make sure copies of the original operating system disk (or CD) are available. If
it becomes necessary to install one or more components that were left out
during the original installation, the computer might require verification of
serial numbers, installation IDs, or the original distribution disk before any
additional files can be installed. You should also create a rescue disk for your
version of Windows for the machine you are repairing in case there are any
problems with corrupt files in the operating system. It is a good practice to
ensure that you have this disk available.
NOTE
A rescue disk contains a computer's configuration information, so
it is usually unique to the computer for which it was created.
Therefore, you should make a new one for each computer you
service. It should be updated any time the system configuration is
modified.
Disassembly
Disassembling a computer is a straightforward task. In most cases, you need to
remove little more than the outer cover of the case to gain access to the
memory, expansions slots and cards, and the CPU (central processing unit).
Because there are many manufacturers, each seeking to establish its own
unique marketing identity, each brand has some custom components or layout.
The best strategy for efficient disassembly is locating and using the manual
that came with the computer.
Often, manuals don't provide a lot of technical information, but they usually
tell you how to remove the cover. The extent to which you have to
disassemble a computer depends on the specific problem or repair. Following
the procedure outlined here will help you establish a routine for completely
and efficiently disassembling most computers:
1. Make a complete backup of necessary operating system and working files.
2. Document the system (hardware and software).
3. Create a clean work area with plenty of room and light.
4. Gather all the necessary tools for the job.
5. Implement all proper safety procedures.
6. Turn off the computer.
7. Disconnect the power cables.
8. Wear an antistatic wrist strap.
9. Locate the screws for the cover—check the manual to discover the
location of the screws (sides or back).
10. Remove the screws. It's a good idea to store them in a box or plastic tube
to keep them from getting lost.
11. Remove the cover from the computer.
12. Document the location of expansion cards and drives.
13. Remove all the cards and place them in antistatic bags.
14. Document the location and connections for each drive (pay special
attention to the red wire on the data cables—this identifies the location of
pin 1 on the device and driver).
15. Remove the data and power supply cables.
16. Remove the drives from their appropriate bays—look on their sides for
the screws (check the manuals).
17. Remove the motherboard.
Reassembly
Run the Preassem video located in the Demos folder on the CD accompanying
this book to view a presentation of all the hardware components that go into a
personal computer.
To reassemble a computer, simply follow the same procedures as for
disassembly, but in the reverse order. When installing components, remember
the following:
Do not force connectors into place—if they don't fit easily, they are
probably in the wrong place.
Expansion cards often require some force or side-to-side movement to fit
into place, but do not force them.
When removing cables, remember the pin 1 locations. Check notations on
the circuit boards and look for the red wire on the ribbon cables.
Connect the cables to the drives before installing them in the bays.
Test the system before replacing the cover.
Lesson Summary
The following points summarize the main elements of this lesson:
By following a systematic plan, you can simplify the process of
disassembling and reassembling a computer.
Establishing and maintaining good documentation and having the right
hardware and software tools are the keys to a successful upgrade.
Following safety procedures will ensure that no damage is done to you or
the computer.
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Lesson 2: Upgrading a Computer
In today's world of constant change, the task most frequently performed by a
computer professional is upgrading old systems to the latest technologies. This
ability to expand and upgrade a computer can prolong the life and utility of a
system. However, sometimes even the simple addition of a new piece of
software can lead to hardware conflicts and the subsequent need for an
upgrade, as a computer owner tries to squeeze one more year out of "old
faithful." This lesson discusses many aspects of computer hardware upgrades.
After this lesson, you will be able to
Describe the principles behind upgrading a computer
Define the limits of and expectations for upgrading a system
Estimated lesson time: 30 minutes
Run the Mboard video located in the Demos folder on the CD accompanying
this book to view a presentation of a personal computer's motherboard
subsystem.
Run the Assembly video located in the Demos folder on the CD accompanying
this book to view a presentation of components being assembled into a
personal computer.
As discussed in Lesson 1, before you begin to upgrade any computer, you need
to document the system. You should create and maintain files that document
all computers for which you are responsible. Figure 20.1 provides a sample
configuration sheet. Use it as a model to create your own.
Figure 20.1 Sample configuration sheet
Memory, Memory, Memory
Does this computer have enough memory? This is the question that most
frequently causes users to seek a computer upgrade. As programs and
hardware get faster and are required to process more graphics and animation,
the need for memory is as important as the need for speed.
Memory upgrades are perhaps the simplest to perform, but they can be very
confusing without advance planning. Purchasing the right memory for the job
is more than half the process of the upgrade. Before installing memory, there
are five things to consider:
Memory chip format
Memory speed
EDO RAM (extended data out random access memory)
Parity
Cache memory
The best source of information—which should be checked before obtaining
memory—is the documentation that comes with the computer's motherboard.
This source generally lists the type of memory required, the proper population
scheme, and the location on the motherboard. If this information is not
available, open the case and look. Some documentation provides a chart that
includes exactly what memory has been installed and what is needed to
upgrade to a given level.
NOTE
You can add memory with SIMMs (single inline memory modules)
or DIMMs (dual inline memory modules).
SIMM Formats
SIMMs come in two basic, physical formats: a 30-pin and a 72-pin chip. Format
is the first consideration, because the chips must fit into the motherboard. This
configuration, along with the size of the processor, determines how many
SIMMs are required to fill one bank.
The 30-pin formats contain memory in 8-bit chunks. This means that a 32-bit
processor requires four SIMMs to fill one bank. Typical 32-bit processors
consist of two banks of SIMMs and, therefore, eight slots (see Figure 20.2).
Figure 20.2 30-pin SIMM
A 72-pin format is larger and supplies memory in 32-bit chunks. Only one
SIMM is required for a 32-bit machine. Pentium processors have a 64-bit data
path and require a 72-pin SIMM (see Figure 20.3).
Figure 20.3 72-pin SIMM
Memory is normally sold in multiples of 8 MB. However, some older machines
will have 8 MB of "on-board" memory (usually soldered in place on the
motherboard). When memory is soldered in place, it cannot be changed;
however, you can disable it. A computer equipped with this on-board memory
can provide 8 MB of memory to the system without having any SIMMs installed
in the slots. For such computers, installing 16 MB of RAM (random access
memory) would yield a total of 24 MB of RAM; if 64 MB were to be added, the
total RAM would be 72 MB, and so on. You won't likely find hardwired memory
on a system anymore unless the PC is very old.
DIMM Formats
DIMMs are much easier than SIMMS to install or remove, because they come
in a single card, which is simply pushed into a module slot. The "key" cut into
the edge that goes into the slot prevents the card from being inserted the
wrong way. The one problem you face is choosing from the wide variety of
memory types available. When ordering a new DIMM, you must know exactly
the memory type supported by the system on which you wish to install the
memory. DIMMs are found in larger memory sizes than SIMMs, ranging to 256
MB and beyond for single cards.
Memory Speed
Memory speed is the amount of time required to access data measured in
nanoseconds (ns); each nanosecond equals one billionth of a second. Two
important considerations arise when addressing memory speed:
The lower the number, the faster the chip speed.
All chips in the same computer should run at the same speed.
Typical chip speeds are 50, 60, 70, and 80 ns. Be sure to check the
motherboard documentation or the existing chips to determine the correct
speed to use.
EDO RAM
The EDO RAM chip is used extensively with Pentium processors. This chip can
improve read times and overall performance by up to 30 percent. This
performance gain is possible because the chip continues to output data from
one address while setting up a new address.
Parity
Parity is used to check the reliability of data. It requires one additional bit
(chip). Memory can be purchased with or without parity. With parity, it will
cost about 10 percent more. Be sure to check the machine specifications or the
existing chips to determine if parity is required. Parity and nonparity chips
cannot be mixed; however, some computers allow parity to be turned on or off
in the BIOS (basic input/output system) setup.
Cache
Cache memory can be found as either L1 or L2. The L1 cache is built into the
processor and cannot be changed. The L2 cache, on the other hand, can be
built into the processor, built onto the motherboard, or sometimes both. In
most cases, cache memory is fixed, but some machines allow the L2 cache to
be upgraded or expanded. Cache memory is sometimes found on older
motherboards (as DIPs, or dual inline packages). Check the motherboard
documentation to determine what, if any, upgrades can be made to the cache.
IMPORTANT
Take special care when installing DIP chips. They are sensitive to
ESD, can easily be installed backwards (look for pin 1 alignment),
and the pins can be broken or bent during insertion.
Installing RAM
Installing RAM is a simple process. The only problem is that the slots are not
always easily accessible. Sometimes you will need to relocate wires
temporarily or even remove expansion cards. This simple procedure usually
works:
1. Turn off the computer.
2. Disconnect all external devices (alternating current [AC] power and
monitor power).
3. Follow the appropriate ESD safety procedures.
4. Remove the cover of the computer.
5. Locate the SIMM banks and determine that you have the correct size,
speed, and quantity of SIMMs.
6. Insert the SIMM in the slot at a 45-degree angle (backwards) and then
snap it into the upright position, as shown in Figure 20.4. Be sure that
the notch in the SIMM matches the slot. If it doesn't fit easily, it is
probably installed incorrectly.
Figure 20.4 Installing a SIMM
7. When the SIMM is in an upright position, be sure that the metal retaining
clip snaps into position. This clip holds the SIMM in place and must be
opened before any SIMM can be removed.
8. Replace any temporarily removed or relocated wires or expansion cards.
Check others to make sure they have not been loosened or disconnected.
9. Replace the cover of the computer.
10. Reconnect the power, monitor, and any other needed external devices,
and start the computer.
The computer should recognize the new memory and either make the
correction or automatically go to the CMOS Setup program. In many cases,
you need only exit Setup to save the changes.
CPU Upgrades
Installing a new CPU is becoming less common as prices of new
motherboard/CPU combinations, and even new machines, continue to drop. In
many cases, installing additi