Copyright © 2008 Apple Inc. All rights reserved

Copyright © 2008 Apple Inc. All rights reserved
Underlying Technologies
Getting Started
Welcome to the Underlying Technologies course. This
course will review the primary technologies used in
Apple products.
Target Audience
This course is intended for technicians who support and service Apple products.
Prerequisite Courses
Basic Computer Theory and Terms
Time Required
3 hours
Course Objectives
Describe the following technologies:
ALS (Ambient Light Sensor)
Match customer issues to related technologies.
Optical audio
Optical drives
Serial Attached SCSI (SAS)
Sound in/out
(analog, digital, optical)
Sudden Motion Sensor
Video in/out
Universal Binaries
Return to top
Next: Technologies Overview
Technologies Overview
This course gives you basic information on the technologies used by Apple products.
Understanding how these technologies work and where they are used are necessary components in becoming
a skilled service technician.
This section includes the protocols and hardware used in hard-wired connectivity. USB, FireWire, Ethernet,
etc., are used to connect a Mac to a peripheral or network.
AGP, PCI, and ATA, are used inside the Mac for data transfer between different parts of the system.
This section includes AirPort, Bluetooth, and infrared.
Power Management
This section covers basic power management on Mac computers. This includes review of power issue
symptoms and how they can be corrected via reset procedures.
This section includes various technologies such as EFI and Open Firmware and introduces you to Apple
diagnostics external to the Mac OS.
Rosetta and Universal Binaries describe aspects of Apple's move to Intel processors.
Back to top
Next: Course Exercise
Print this page and answer the following questions.
1. You are replacing a customer’s drive. Which of the following requires a parallel ATA replacement?
PowerMac G5
PowerMac G4
2. What might be the consequences of trying to use Full Duplex communication in a shared Ethernet
3. Fill in the blanks:
Most Apple products provide either FireWire 400. or both FireWire 400 ( ____ Megabits per second, 4
and __ pin connectors) and FireWire 800 (800 Megabits per second, __ pin connector). FireWire 800
is____________compatible and allows the connection of a FireWire 400_____________.
4. Target Disk mode has two primary uses:
5. Optical digital audio in and out ports are known as:
Torline ports
Toslink ports
Trolink ports
6. Some peripherals work with the slower USB data-transfer rate of 12 Mbit/s. These include:
______________ and _______________.
7. Which is true?
a) USB devices use two types of plugs, Type A and Type B. The Type A plug is dome-shaped and
connects to the host computer or a downstream hub. The Type B plug, which is flat, connects upstream
to the USB device.
b) USB devices use two types of plugs, Type A and Type B. The Type A plug is flat and connects to
the host computer or an upstream hub. The Type B plug, which is somewhat house-shaped, connects
downstream to the USB device.
8. The _________________ allows you to set up multiple monitors in two ways,
9. ______________offers low power consumption but has a reduced range when compared to
AirPort/AirPort Extreme.
10. Name a Mac on which you can reset the PMU without opening the computer and one that requires
opening the computer.
11. ALS_____________________governs the illumination of the backlit keyboard and the brightness of
the screen.
12. Which type of compression removes some non-redundant content from the original, which results in
reduced quality of the compressed file?
13. Apple-developed CUPS (___________________) is a cross-platform, portable printing software layer
for UNIX-based operating systems.
14. Open Firmware Access - You can start up into Open Firmware by holding down:
Command-Option <esc>
15. The counterpart to Open Firmware for Intel-based Mac computers is:
16. With the introduction of the Mac mini model with an optional DVD+/-RW/CD-RW SuperDrive, Apple
now supports ___________________discs of both + and - types.
17. The Sudden Motion Sensor does not prevent _________________ failures.
18. Which runs natively on either PowerPC or Intel-based Mac computers?
Universal Binary
Binary Translation
Binary Application
19. Match the Customer Issue to the related Technology:
a) Trouble connecting scanner to Mac
1. Ambient Light Sensor
b) Cannot boot up
2. Infrared
c) Screen too dim to read on airplane
3. Rosetta
d) Remote can’t turn on Apple TV
4. USB/Firewire
e) Older application won’t run on MacBook
5. Open Firmware
Parallel ATA
Introduction of Serial ATA (SATA)
Parallel and Serial ATA Compared
Cable Compared
Serial ATA Power and Data Cables
Troubleshooting and Repair Significance
Parallel ATA
The Advanced Technology Attachment (ATA) interface called Integrated Drive Electronics (IDE) by some
companies, has existed in substantially the same form since 1989, and has become the highest-volume disk
drive interface in production.
Over the years, many hard drive companies have continuously improved parallel ATA and extended its data
transfer rate from 3.3 megabytes per second (MB/s) to 133 MB/s.
Introduction of Serial ATA (SATA)
Apple introduced a hard disk interface called Serial ATA with the release of the original Power Mac G5. This
interface offered a number of advantages over parallel ATA including:
Data transfer speeds of up to 1.5 Gb/s (150 MB/s)
A new data and power cable
Lower power consumption
Note: Previous hard disk interfaces such as ATA/66, ATA/100, and ATA/133 are all considered parallel ATA
interfaces. This is because these interfaces use many individual wires to carry data in parallel between the
disk and the host computer. Serial ATA uses less wires to carry this data in serial form to improve throughput
and speed.
Serial ATA is also called:
Parallel and Serial ATA Compared
The table below shows some of the differences between parallel and serial ATA interfaces:
Parallel ATA
Maximum Speed
1.33 Gb/s (133 MB/s)
Maximum Cable Length 0.45 meters
Hot Pluggable
Maximum Drives per
Signaling Voltages
Serial ATA
1.5 Gb/s (150 MB/s)
1.0 meter
0.25 V
Pins per Channel
* The Serial ATA specification includes support for hot pluggable hard disks, however the Power Mac G5 did
not support this feature. This is listed here for specification comparison only.
Cables Compared
The cable types for Parallel ATA and Serial ATA are very different. The image below shows a comparison
between parallel (left) and serial (right) ATA data cables:
Serial ATA Power and Data Cables
There are two types of Serial ATA cables. The data cable and the power cable:
Serial ATA Power Cable and Serial ATA Data Cable
Troubleshooting and Repair Significance
Being able to identify ATA and SATA drives will eliminate confusion when replacing hard drives.
Knowing that two ATA drives can be attached to one cable enables you to correctly replace hard drives
in computers supporting Parallel ATA.
Knowing the differences in performance can enable you to correctly set customer expectations on drive
You now know how to identify data and power cables for Serial ATA drives.
You now know how to distinguish ATA and SATA data cables.
Back to top
Next: Ethernet
RJ-45 Connector
Cat 5
Cat 5e and Cat 6
Half-Duplex and Full-Duplex
Additional References
Troubleshooting and Repair Significance
Ethernet is a family of computer network technologies for LANs (Local Area Networks.)
Most recent Apple computers come with built-in 10/100/1000 megabit per second (Mbps) twisted-pair
Ethernet networking capability, which you can use to connect to a wired network.
10Base-T, 100Base-T, and 1000Base-T networks use twisted pairs of cable wrapped around each other to
form one single cable.
RJ-45 Connector
The ends of a 10Base-T or 100Base-T cable have an RJ-45 style connector.
The RJ-45 connector is similar to a phone cable, except larger and wider. RJ-45 plugs have room for up to 8
wires where phone cords (which use RJ-11 connectors) only have space for 4 wires. RJ-45 is the standard for
10Base-T or 100Base-T networking.
Front and Side of RJ-45
Cat 5
Connect to a 100Base-T network only with category 5 (also called cat 5) wire designed to carry the more
sensitive 100Base-T signals.
NOTE: If older wire is used data transmission problems may occur.
Cat 5e and Cat 6
You should connect to 1000Base-T (Gigabit Ethernet) network using only category 5e (also called cat 5e) or
cat 6 cabling.
Half-Duplex and Full-Duplex
The Apple Ethernet Drivers included with the Mac OS support both half- and full-duplex Ethernet
In half-duplex Ethernet data transmission, only one node (computer, printer, etc.) is transmitting data on an
Ethernet segment at a time.
In full-duplex communication, a single node can simultaneously transmit and receive data to and from
another single node.
This significantly increases data throughput.
Full duplex requires the following configuration:
1. Each node must be its own Ethernet segment or collision domain and not connected to a shared
2. Each node must support full-duplex communication and be configured to do so. All recent Mac
computers support full-duplex communication.
Ethernet Topologies
Most modern Ethernet environments use switched Ethernet hubs for primary connectivity.
In this environment, the network is more dependent on the abilities of these Ethernet switched hubs to
properly buffer data to and from each node in order to maintain two-way data transmissions.
This is in direct contrast to the data throttling capabilities of half-duplex.
Avoiding Wrong Configurations
It's important to realize that, if full-duplex communication was attempted in an environment that does not
support it (i.e. a shared Ethernet segment), or if some nodes in a network environment were configured for
full-duplex while others were configured for half-duplex, massive data collisions and errors would occur
causing significant slowdown in overall throughput.
You can check for such errors using the Network Utility in Mac OS X. A good understanding of your
Ethernet topology and environment as well as the capabilities of each node is necessary before attempting to
configure and use full-duplex communication.
Additional References
Read the Apple support document TA26002 titled 'Gigabit Ethernet: A Brief Description'.
When connecting two computer products via Ethernet, it may be necessary to use an Ethernet crossover cable.
Older Apple products require this while later Apple products do not. Review the Apple support document
HT2274 titled 'Apple products that require an Ethernet crossover cable' for more information on this topic.
Also, read the Apple support article HT1433 titled 'Creating a small Ethernet network', to get a sense of the
physical cabling options.
Troubleshooting and Repair Significance
Ethernet cables themselves can be the source of connectivity issues.
A low quality cable will impact data transfer rates.
You can identify computer models that require Ethernet cross-over cables.
You can identify three versions of Ethernet.
Back to top
Next: ExpressCard/34
About ExpressCard/34
ExpressCard/34 Specifications
Insertion and Removal
About ExpressCard/34
The MacBook Pro introduced support for ExpressCard/34 modules.
ExpressCard/34 is a standard of mobile expansion card architecture created by the Personal Computer
Memory Card International Association (PCMCIA).
The ExpressCard/34 slot on the MacBook Pro is directly connected to the computer through the PCI Express
bus, so the computer doesn't need to use a PCI bridge chip to communicate between the system controller and
the portable's expansion slot.
Some other advantages of the ExpressCard/34 over PC Cards (including CardBus cards) include:
More rugged than PC cards.
Roughly half the size of PC cards.
Uses a PCI Express bus connection to the computer providing higher bandwidth than PC cards.
Uses less power than PC cards.
Currently there are a number of ExpressCard/34 modules starting to become available in the market. These
Flash Card Adapters
TV Tuner modules
Broadband wireless cards (EDGE, EV/DO, etc.)
Flash memory modules
GPS receivers
Always check to make sure the manufacturer of a given ExpressCard/34 supports Mac OS X.
ExpressCard/34 Specification
There are two sizes of ExpressCard/34 modules; ExpressCard/34 and ExpressCard/54. Here is an example of
an ExpressCard/34 module:
IMPORTANT: The MacBook Pro has a single 34mm ExpressCard slot. It can only accept ExpressCard/34
modules. ExpressCard/54 modules may fit partially into the slot but will not reach far enough to make a
ExpressCard interface specifications are:
ExpressCard/34 Module ExpressCard/54 Module
Card dimensions
Card thickness
26-pin "beam on blade" connector
Connector style
Bus type
Bus bandwidth
Avg. power
PCI Express (1-lane)
2.5 Gb/sec
3.3 V - 1000 mA
3.3 V aux - 250 mA
1.5 V - 500 mA
Insertion & Removal
It is important to always properly insert and remove an ExpressCard module, to ensure proper module
connectivity and to avoid damage to the module and the slot's internal connector or latching mechanism.
The slot has a spring-loaded latching mechanism that is reminiscent of a cupboard door latch: Push in and
latch to insert, push in again and spring outward to remove.
To Insert an ExpressCard module:
Gently slide the module, face up, into the slot directly over the ExpressCard slot door. The door should
swing down, allowing the module to be inserted.
Continue to gently push the module into the slot almost all the way in, until you encounter some
Gently push just a bit more firmly and the module will slide just a bit further into the slot, with a
spring-loaded feel to the resistance.
Once you reach the point of maximum insertion, you will not be able to push the module in any further
and you should hear a slight click.
At this point, gently release the module and it should slide just a bit outward and then click into place.
The module is now properly inserted and latched.
Depending on the functionality of the module, and preference settings, an icon of the inserted module
may appear on the Mac OS X desktop.
To remove an ExpressCard module:
Be sure to first dismount the module's icon from the Mac OS X desktop, by dragging its icon to the
Gently but firmly push inwards on the module and the module will slide just a bit further into the slot,
with a spring-loaded feel to the resistance.
Once you reach the point of maximum insertion, you will not be able to push the module in any further
and you should hear a slight click.
Gently release the card and it should slide just a bit outward and then click again.
Continue to pull the module gently outward to remove it form the slot.
Do not simply pull the module out of the slot without unlatching it in this way first, as doing so may
damage the module and/or the internal ExpressCard connector or latching mechanism.
Back to top
Next: FireWire
FireWire Overview
FireWire 400 and FireWire 800
FireWire Connectors
FireWire 400 Cabling
FireWire 800 Cabling
Daisy Chaining
Target Disk Mode
Target Disk Mode for Optical Drive Access
Further Reading
Troubleshooting and Repair Significance
FireWire Overview
"FireWire" (and the "FireWire" logo) is a licensed and copyrighted term used by Apple.
IEEE 1394 and FireWire refer to the same technology.
Apple was the principle creator of IEEE 1394 specification.
The technology is now used by many other computer platforms including Intel and Microsoft.
FireWire technology enables high-speed communications and fast data transfer.
FireWire devices use peer-to-peer technology i.e., they communicate with each other without permission
from a host computer.
FireWire also supplies more power than USB, requires no ID switches or termination, and is hot-pluggable.
FireWire 400 and FireWire 800
Most Apple products provide either FireWire 400 or FireWire 800 connectivity.
Here is a comparison of these standards:
FireWire 400
IEEE 1394a Standard
Up to 400 Megabits per second
supports 4-pin and six-pin connectors
FireWire 800
IEEE 1394b Standard
Up to 800 Megabits per second
requires 9-pin connector
FireWire Connectors
Firewire 400 supports two different connectors:
four-pin (data-only)
six-pin (data and power)
FireWire 800 requires a nine-pin connector
nine-pin data and power
FireWire 800 is backwards compatible and allows the connection of a FireWire 400 peripheral.
FireWire 400 Cabling
six-pin-to-six-pin (allows data and power connection from FW400 port to FW400 peripheral)
six-pin-to-four-pin (allows data-only connection from FW400 port to FW400 peripheral)
FireWire 800 Cabling
nine-pin-to-four-pin (allows data connection only from FW 800 port to FW 400 peripheral)
nine-pin-to-six pin (allows data and power connection of a FW 800 port to a FW 400 peripheral)
nine pin to nine pin (allows FW 800 connection)
Daisy Chaining
FireWire devices can be daisy chained together. Most FireWire devices come with two ports. You can run
one port to your Mac and the other can go to another device.
However, there are some rules to keep in mind.
Devices should be arranged in the chain from fastest to slowest.
Cables should not be longer than 15 feet.
While you can have 63 devices on one port or bus, the longest path can be only 16 devices. A hub can
be used to avoid this situation.
When you connect a FireWire device, it makes itself known with an ID number and lets the bus know
whether it will communicate at 100, 200, 400, or 800 megabits.
Target Disk Mode
When a Mac is in Target Disk mode and connected to another Mac by a FireWire cable, the original computer
operates like a FireWire mass storage device.
Target Disk mode has two primary uses:
high-speed data transfer between computers
diagnosis and repair of a corrupted internal hard drive
The original computer can operate in Target Disk Mode as long as the other computer has FireWire 2.3 or
To put the computer into Target Disk mode, the user holds down the T key while the computer is starting up.
When Open Firmware detects the T key during the boot process, it transfers control to special Open Firmware
To take the computer out of Target Disk mode, the user presses the power button.
NOTE: OS X 10.3.9 or earlier cannot mount volumes from an Intel-based Mac in Target Disk Mode. Also,
Target Disk Mode is not used with the MacBook Air.
Target Disk Mode for Optical Drive Access
Target Disk Mode can be used during troubleshooting, for accessing and booting to optical discs in optical
drives, as well as accessing and booting to internal hard drives.
You can use this approach in situations where you don't have access to a computer's internal optical drive and
wish to run diagnostics on that computer.
Further Reading
Review the Apple support article HT1661 titled 'How to use and troubleshoot FireWire target disk
Troubleshooting and Repair Significance
Starting up a Mac in Target Disk Mode is a powerful troubleshooting technique.
Being able to identify different FireWire cable setups avoids mismatches that waste time.
Target disk mode can also be used to access optical drive based diagnostics for Mac computers that do
not have a functioning optical drive.
Back to top
Next: Optical Audio
Optical Audio
Further Reading
Troubleshooting and Repair Significance
Starting with the Power Mac G5 and iMac G5, some Mac computers came equipped with optical digital audio
in and out ports. (also known as 'Toslink' ports).
These use the Sony/Philips Digital Interface (S/PDIF) protocol over optical cables for connecting to devices
such as decks, receivers and 5.1 surround-sound speaker systems.
Optical minijack connector
Since optical digital audio transmits data as impulses of light rather than electrical signals, it enables true
noise-free sound, eliminating ground loops.
Further Reading
TA26828 Macintosh: How to Connect Audio Devices to Your Computer
TA27095 Power Mac G5: Optical Audio Port Specifications
TA47850 Playing DTS audio files with iTunes.
Troubleshooting and Repair Significance
Optical audio ports can be a factor in troubleshooting certain audio issues.
Back to top
Next: SD Card Slot
Serial Attached SCSI
Troubleshooting and Repair Significance
With the introduction of the Xserve (Late 2006) and continuing with later Xserve models, Apple provides a
drive bay that was compatible with Serial Attached SCSI (SAS) drives.
The Mac Pro (Early 2008) also supports SAS drives installed into its four internal drive bays, but only if the
Apple Mac Pro RAID card is also installed to support these drives.
For more information please refer to the following Apple support article HT1346:
"Mac Pro RAID Card and Xserve RAID Card: Frequently Asked Questions (FAQ)"
SAS is the next generation of SCSI drives providing the serial communication protocol used for direct
attached storage. SAS utilizes a 3 Gbps link and the same physical connection layer as SATA.
For more information on SAS, see the Serial Attached SCSI website (
Troubleshooting and Repair Significance
Knowing that two different drive types can be used in Xserve (Late 2006), Xserve (Early 2008), and
Mac Pro (Early 2008) computers can avoid confusion when determining drive compatibility.
Back to top
Next: Sound In/Out
SD Card Slot
SD Card Slot Overview
Using the SD Card Slot
SD Card Slot Overview
Beginning with portables released in mid-2009, some Apple portable models include an SD card slot, in place
of the ExpressCard slot in previous portable models. This slot works just like an SD card reader attached to the
external USB bus on any other Mac OS X-based computer. Drivers for this interface are included in Mac OS
X. Boot Camp also supports this interface.
SD cards are used for media storage in most digital cameras and camcorders. The SD card slot allows for quick
and easy transfer of media and data with no external card reader or cable required.
For more information about the SD card slot and how to use it, please refer to the following Apple support
article HT3553:
"About the SD card slot in MacBook Pro (15-inch, 2.53GHz, Mid 2009), MacBook Pro (15-inch, Mid 2009),
and MacBook Pro (13-inch, Mid 2009)"
Typical SD Card
SD Card inserted in SD card slot
The SD card slot is designed to work with industry standard SD cards. You can also use miniSD and microSD
cards with the proper adapter(s). Larger cards such as CompactFlash™ or Sony Memory Stick™® are not
supported. XD-Picture cards are also not supported. Use a third-party card reader attached to the USB or
FireWire port on the computer to read these card types.
Examples of Card Types Not Supported in the SD Card Slot
Using the SD Card Slot
To insert the card:
1. Align the "cut corner" short side of the card towards the slot. The metal contacts on the card should face
2. Push the card into the slot until it stops.
Card insertion tips:
When inserted, the SD card will stick out a bit from the port. It will not be flush with the computer
Do not force the card into the slot. If the card does not fit, try reorienting the card so the cut corner faces
the other side of the slot. If the card still does not fit, try another card.
To eject the card:
1. Perform one of the following steps as you would to eject a USB drive:
Drag the card icon to the eject icon in the Dock.
Press the eject icon next to the card icon in the Finder sidebar.
Select the volume icon and choose File > Eject in the Finder.
2. After the card unmounts, pull the card out of the computer.
Card removal tips:
There is no eject button or mechanical eject mechanism for the SD card slot. Simply pull the card out of
the slot by grasping the edge of the card that protrudes from the computer.
Format the card just like any other removable volume, using Disk Utility.
Keep in mind that if you want to use the SD card in a camera, you may need to reformat the card directly
from the camera before recording footage. Consult the documentation that came with the camera for
more information.
SD Card Slot Troubleshooting
Here are some troubleshooting tips you should try if you are experiencing issues with the SD card slot:
If there are images on the SD card, Image Capture or iPhoto may open. This is expected behavior,
especially if the card was used in a digital camera.
You can start up the computer from the SD card if the card is large enough and formatted correctly.
The SD card and built-in reader should appear in System Profiler on the built-in USB bus, as shown
If the card does not appear in System Profiler, try reformatting the card using Disk Utility, or try another
SD card without using an XD or mini SD adapter.
If the card reader does not appear in System Profiler on the USB bus, try resetting PRAM or SMC, or try
starting up from another volume such as the Mac OS X Installer DVD to check System Profiler from a
known-good operating system.
Return to top
Next: Serial Attached SCSI
Sound In/Out
Further Reading
Troubleshooting and Repair Significance
You can connect a microphone, VCR, tape deck, or audio CD player to a Mac and send the sound signal from
the device into the computer, where the audio can be recorded and manipulated digitally.
All Mac computers have built-in speakers. You can also attach amplified speakers or headphones.
Most current and in-warranty Mac desktops and portables have sound input and output jacks. The sound input
and output ports use stereo mini plug connectors.
The computer's audio input and output capabilities feature 16-bit stereo sound with 44.1 kilohertz (kHz) and
22 kHz sampling rates.
Most of the recent Mac computers with built-in displays come with a tiny built-in microphone that resembles
a small hole in the display bezel.
To use a sound input device other than the built-in microphone, select the input source in the Sound pane of
System Preferences.
Further Reading
TA26828 How to Connect Audio Devices to Your Computer
Troubleshooting and Repair Significance
Being able to identify all the configuration options available for both sound input and output, as well as
knowing if the Mac in question has a built-in mic or not, will assist you in solving simple audio issues.
Back to top
Next: USB/USB 2.0
USB 2.0
USB Names
USB Connectors
USB Components
Rules for a USB Chain
Connecting Multiple USB Devices
Troubleshooting USB Issues
Troubleshooting and Repair Significance
USB, built in to all Mac computers - often with two USB ports, allows you to connect a variety of devices,
such as printers, scanners, external etc.
Mac OS X includes several USB kernel extensions, providing access to USB keyboards and other devices
very early in the startup process.
USB 2.0
USB 2.0 devices can transfer data at a rate of 480 Mbit/s.
Some types of peripherals may be available with either the fast data-transfer rate of 480 Mbit/s or the slower
data-transfer rate of 12 Mbit/s.
These include:
Digital cameras
CD-ROM burners
DVD drives
Flash card readers
Other peripherals operate at slower rates because these peripherals do not need fast data transfer rates. They
operate at the two lower rates of either 1.5 or 12 Mbit/s.
These include:
USB Names
Here are the different USB transfer rates:
Low-speed devices (1.5 Mbit/s)
Full-speed devices (12 Mbit/s)
High-speed devices (480 Mbit/s)
The correct label for high-speed USB products is "Hi-Speed USB." Certified products that support high-speed
data rates will use a blue and red logo.
The correct label for low or full-speed USB products is simply "USB." Certified products that support low- or
full-speed data transfers will have this logo:
In the older USB 1.0 and 1.1 specs, 12 Mbit/s devices were referred to as "high speed devices." With the USB
2.0 spec, these are now called "full speed devices."
USB Connectors
USB devices use two types of plugs, Type A and Type B. The Type A plug is flat and connects to the host
computer or an upstream hub. The Type B plug, which is somewhat house-shaped, connects downstream to
the USB device.
Type A USB Plug
Type B USB Plug
The USB root hub in the computer is set to support remote wake-up whenever a device is attached to or
disconnected from the bus.
USB Components
USB requires several components:
Operating system support.
Mac OS has supported USB since Mac OS version 8.1.
A host to control the USB system and manage connected USB devices. A USB chain can have only
one host (typically, a controller chipset in the computer), which is why USB can't connect computers—
hosts—to each other, even though its data transfer speeds can be comparable to Ethernet. The USB host
typically provides two or four Type A ports connected to an internal hub.
A hub, for connecting USB devices. Only hubs have Type A ports, so if you see a peripheral such as a
keyboard or display with Type A ports for additional devices, it must have its own internal hub.
Rules for a USB Chain
When you connect USB devices in a chain:
There can be a maximum of 127 devices attached to one USB bus.
There can be a maximum of six tiers, including the root hub inside the computer. This can be tricky to
track sometimes, since hubs can be hidden inside the computer or on displays, keyboards, and so on.
Bus-powered hubs can't connect to other bus-powered hubs, because the bus doesn't provide enough
power. A keyboard with an internal hub is a good example of a bus-powered hub. Instead, to extend the
chain of USB devices, you have to alternate self-powered and bus-powered hubs, or use all selfpowered hubs.
USB cables can be up to 16 feet long and typically come in approximately 3-, 6-, 10-, and 16-foot
Connecting Multiple USB Devices
To connect more than one USB device to a computer with a single USB port, use a USB hub. You connect
USB devices to the hub, and then connect the hub to the computer. You don't need to install any software to
use a USB hub.
Although USB supports “hot-plugging,” do not detach a USB device such as a hard disk drive or scanner
while it is operating.
For a deeper understanding of USB, read the four frequently asked questions documents and review the
Apple Developers' USB site:
TA24945 USB: FAQ (1 of 4)
TA24948 USB: FAQ (2 of 4)
TA24951 USB: FAQ (3 of 4)
TA24953 USB: FAQ (4 of 4)
Troubleshooting USB Issues
The following are some of the common issues that you may encounter when dealing with USB devices:
Not Enough Power to Function
The Mac OS will generate a "Not Enough Power to Function" message if:
A device tries to draw too much power from the USB bus.
One or more devices plugged into a hub requires more power than is available.
You have attached a self-powered device (like a printer or floppy drive) and forgot to plug it into
an electrical outlet.
If you're using a self-powered device, make sure it is plugged into a working electrical outlet. If not, try
connecting the device directly to your computer or to a port on a powered hub. If you're connecting the
USB device to a powered hub, make sure the hub is plugged into a working electrical outlet.
Not Enough Power For All Functions
The Mac OS will generate a "Not Enough Power for All Functions" message if there is enough power
to supply some but not all of the functions the device is designed to provide.
As above, you'll need to see if the USB device has its own power cord and, if it does, you'll need to
plug it into a working electrical outlet. Also, try plugging the cable for the USB device directly into to
your computer or to an available port on a powered hub. If you're connecting the USB device to a
powered hub, make sure the hub is plugged into a working electrical outlet.
Troubleshooting and Repair Significance
Knowing the different USB standards, connectors and how they operate together will enable you to
correctly set up USB chains.
Back to top
Next: Video In/Out
Video In/Out
Attaching an External Display
External Display
Extended Desktop and Video Mirroring
Digital Video vs. Analog Video Capture
Further Reading
Troubleshooting and Repair Significance
Attaching an External Display
Apple computers have used several ways to deliver the video signal to an external display such as a
television, VCR, projector, or external display.
The following are ports used by Mac computers:
VGA/SVGA You can send the RGB signal through the VGA/SVGA port to Apple and third-party
RGB displays, as well as to televisions and projectors that support RGB video input.
S-video You can send the signal through the S-video port to VCRs, televisions, and projectors with Svideo ports.
Mini-DVI Later Mac computers offered a Mini-DVI port that could connect to either a Mini-DVI to
DVI adapter or a Mini-DVI to VGA adapter.
1. Mini-DVI to DVI
2. Mini-DVI to VGA
Mini DisplayPort Some Late 2008 Mac portable computers introduced an Apple-proprietary port
called Mini DisplayPort.
This port also requires adapters to connect to VGA or DVI displays.
Mini Display Port
The Apple LED Cinema Display (24-inch) uses a Mini DisplayPort as its video connection interface.
Many current Apple computers have video-in via FireWire.
External Display
Many portable models have a video-out port, so you can connect a monitor directly with a VGA-style adapter
(shown above) or other external video device, such as a video projector.
Detailed information on adapter options can be found by checking the specifications at the Apple
Specifications website:
Extended Desktop and Video Mirroring
The Display System Preference allows you to set up multiple monitors in two ways, extended desktop and
video mirroring.
Extended Desktop
Extended desktop uses both displays to create a larger single Desktop. It is enabled by choosing the
Arrangement tab in the Displays System Preference as shown here:
Video Mirroring
Video mirroring means that both displays are showing the exact same image. It is also enabled within the
Arrangement tab of the Display System Preference. There you have the option to select Mirror Displays.
Digital Video vs. Analog Video Capture
FireWire's most popular use to date is the capture and editing of digital video. Digital video capture is also
called DV capture.
Although there are some differences between the methods and equipment needed to capture Digital video,
essentially the process and user experience are similar to capturing and editing Analog video. First lets define
what Analog and Digital video capture means.
Analog video capture - This uses analog video signals. Analog connections include Composite and S-video
type cables/ports.
Digital video capture - Data is transferred in a completely digital format using a high -speed data bus like
FireWire. Digital Video provides a much higher quality of video as well as better speed for capturing the
Important - Remember that a Digital Video cameras will specifically have an IEEE 1394 port on the camera.
You cannot use a "standard" video camera which only has composite or S-video out with a FireWire port.
Further Reading
HT3146 Mac OS X: How to use multiple displays
TS2083 Mac OS X: Multiple displays setup doesn't work
HT1573 Troubleshooting: My computer displays no video
Troubleshooting and Repair Significance
No-video issues occur with some frequency. Understanding basic video connections and settings will
save you time and effort.
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Next: AirPort Extreme
AirPort Extreme
AirPort Extreme is Apple's implementation of Wi-Fi, the IEEE 802.11 wireless networking standard. You
will learn about AirPort Extreme in a separate Wireless Networking course later in this curriculum.
All newer Apple computers support AirPort Extreme.
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Next: Bluetooth
Bluetooth Overview
Bluetooth Support Information
Troubleshooting and Repair Significance
Bluetooth Overview
Bluetooth is a wireless communications protocol often used for connecting peripherals such as headsets,
PDAs, keyboards, and mice to computer systems.
Apple's Wireless Keyboard and Wireless Mouse use Bluetooth.
Bluetooth offers the advantage of low power consumption.
The trade off for low power consumption is a reduced range when compared to AirPort/AirPort Extreme.
Here is a comparison of Bluetooth, AirPort, and AirPort Extreme in both the 802.11g and 802.11n standards:
Bluetooth 1.x
Bluetooth 2.0+EDR
Bluetooth 2.1+EDR
AirPort (802.11b)
AirPort Extreme (802.11g)
AirPort Extreme (802.11n)
Transmission Rate
1 Mbps
3 Mbps
3 Mbps
11 Mbps
54 Mbps
248 Mbps (2x2 antennas)
Later PowerBook and Intel-based Mac computers support the Bluetooth 2.0+EDR standard, and now the
Bluetooth 2.1+EDR standard.
Bluetooth Support Information
Due to the increased use of Bluetooth-enabled peripherals, Apple has provided its customers with an
extensive array of support documentation at the Bluetooth Support site:
In situations where you need to troubleshoot a Bluetooth connectivity or performance issue, this resource is
an excellent first step.
In addition, the Service Manuals for Bluetooth-enabled Mac computers provide troubleshooting steps and
instructions for replacing Bluetooth cards and antennas.
Troubleshooting and Repair Significance
Knowing where to find appropriate support and service resources will save you time when
troubleshooting Bluetooth-related issues.
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Next: Infrared
Infrared Overview
Apple Remote Troubleshooting Tip
Troubleshooting and Repair Significance
Infrared Overview
Some Mac computers use infrared light to exchange information with other devices.
Early Mac computers were equipped with an infrared modem to allow for communication with other
computers or other devices.
Later models of the Mac use infrared technology to communicate with an Apple Remote for control of the
Front Row application used with Apple TV.
Infrared requires line of sight to function and has a relatively short range.
Apple Remote Troubleshooting Tips
Verifying Remote Function
If you have a camera-equipped Mac, you can point an Apple Remote at the camera and see a blinking white
light in your video image. This happens because the video cameras used by Apple can see the infrared light
produced by a functioning Apple Remote.
If you see the blinking light, the Apple Remote has power.
Pairing a Remote
Pairing a remote with a Mac is important in situations where there may be multiple remotes working with
multiple computers. To avoid inadvertent interference with other Mac computers, follow the steps outlined in
the Apple support article HT1619 titled 'Pairing your Apple Remote with your computer'.
Troubleshooting and Repair Significance
You now know how to determine whether an Apple Remote has power and how to pair a remote with a
specific computer.
Back to top
Power Management Overview
Power Management Unit (PMU)
System Management Unit (SMU)
System Management Controller (SMC)
Troubleshooting and Repair Significance
For Further Reading
Power Management Overview
Through the use of the Energy Saver System Preference, you can set up your Mac to use less energy when the
computer is idle or inactive for a specified length of time.
Within this System Preference, you can control when you put the entire computer to sleep, put the display to
sleep, and reduce brightness of the display. Depending on the computer model, this functionality is governed
by a:
Power Management Unit (PMU)
System Management Unit (SMU)
System Management Controller (SMC)
The PMU/SMU/SMC hardware controls all aspects of power consumption inside the computer and responds
to settings chosen in the Mac Energy Saver System Preference and programs
Power Management Unit (PMU)
The Power Management Unit (PMU) is an integrated circuit (computer chip) typically found on a computer's
logic board. As its name implies, the PMU is responsible for managing all aspects of the computer's power.
It controls
hard disk spin down,
sleep and wake,
some charging aspects, and
how any devices attached to the computer affect sleep.
If the settings in the PMU become corrupted, it can result in operational issues such as
your computer not turning on
not displaying video
not waking from sleep
A PMU reset should only be used as a last resort in the case of a hardware failure or when the power
management system is suspected.
NOTE: Resetting the PMU returns the computer hardware, including NVRAM, to default settings and forces
the computer to shut down.
How to Reset PMU
How you perform a PMU reset depends on what Mac you are working on.
For example, an original Mac mini can be reset without opening up the computer.
PMU reset depends on the Mac being worked on.
For example, an original Mac mini can be reset without opening up the computer while an iBook requires
opening the computer in order to access a PMU reset switch.
Here are the reset instructions for several iBook models:
iBook (Dual USB), iBook (Late 2001) and iBook (14.1 LCD)
If the computer is on, turn it off.
Disconnect the AC power adapter.
Remove the battery.
Press and release the reset button (shown below) located above the Audio/Video port on the left side of
the iBook (Dual USB) computer by inserting the end of a paper clip into the small hole and gently
pressing the switch once.
Wait 5 seconds.
Reconnect the AC power adapter.
Put the battery back in the computer.
Press the Power button to restart the iBook computer.
Detail showing PMU button location.
NOTE: Only reset a PMU button ONCE, then wait at least five seconds before attempting to start the
computer up again. This is to give the PMU enough time to start up its internal software and begin monitoring
the hardware.
Pressing a PMU reset button multiple times can crash the PMU's internal software, which can cause any
number of power management issues.
Read and review the Apple support article titled HT1894 'Avoid unnecessarily resetting the SMC or PMU for
troubleshooting purposes' for more information.
System Management Unit (SMU)
The SMU (System Management Unit) controls all power functions on the Mac.
It was introduced in 2004 and was used until the introduction of the Intel-based Mac computers in 2006.
SMU differs from PMU, in that it also controls thermal aspects of the computer, such as fans, blowers and
temperature sensors.
This is required to maintain proper cooling inside newer, faster Mac computers.
Resetting the SMU can resolve some computer issues such as not starting up, not displaying video, sleep
issues, fan noise issues, and so on.
The functions controlled by the SMU include:
Tells Mac when to turn on, turn off, sleep, wake, idle, etc.
Handles system resets from various commands.
Controls the fan.
NOTE: Resetting the SMU does not reset the PRAM. A restart is more effective.
How to Reset SMU
This differs from model to model. Be sure to look up the reset procedure for each model.
System Management Controller (SMC)
In the Intel-based Mac, much of the functionality of the SMU was replaced by the System Management
Controller- the (SMC) - a chip that controls all the power functions including:
Telling the computer when to turn on, turn off, sleep, wake, idle, and so forth.
Handling system resets from various commands.
Controlling the fans.
NOTE: Resetting the SMC does NOT reset the PRAM.
ALSO: Resetting the SMC will not resolve issues in which your computer is unresponsive—in these
situations, restarting your computer is a better choice.
How to Reset SMC
As we saw with PMU and SMU, there are different SMC reset techniques required for different models of
Intel-based Mac computers.
NOTE: Two System Management Controllers in Mac Pro (Early 2009)
The Mac Pro (Early 2009) has two System Management Controllers (SMCs) instead of just one. SMC
functionality is now split between a primary (or master) SMC on the backplane board, and a secondary (or
slave) SMC on the processor board.
Since SMC firmware is stored on both the backplane and processor boards, it is important that the version of
SMC firmware always match on both boards.
Troubleshooting and Repair Significance
You can correctly identify reset procedures
You can correctly identify and isolate power-related issues.
You can readily recognize PMU, SMU, or SMC reset opportunities
For Further Reading
Read and review the following Apple support articles which deal with how to reset a PMU, SMU, or SMC in
an Apple product. For more articles search for 'PMU reset', 'SMU reset', or 'SMC reset' in Knowledge Base:
HT2183 Mac mini: How to reset the PMU
HT1712 Resetting the iMac (Flat Panel) Power Management Unit (PMU)
HT1431 Resetting PowerBook and iBook Power Management Unit (PMU)
HT1767 iMac G5: How to Reset the SMU
HT1436 How to reset the SMU on a Power Mac G5 (Late 2004) or Power Mac G5 (Late 2005)
HT3964 Intel-based Macs: Resetting the System Management Controller (SMC)
Back to top
Next: 32-bit or 64-bit Processor
Ambient Light Sensor
ALS Overview
iMac G5 (Ambient Light Sensor)
ALS Controls for Display and Keyboard
ALS Troubleshooting
Troubleshooting and Repair Significance
ALS Overview
ALS governs the illumination of the backlit keyboards and the brightness of the screen. Two light sensors
provide input to the ALS system. Most recent PowerBook and MacBook Pro models include this feature.
PowerBook (17-inch) showing keyboard illuminated.
iMac G5 (Ambient Light Sensor)
ALS was used in iMac G5 (Ambient Light Sensor) system to measure the amount of light in a room and
determine how bright the sleep indicator lights should be when the computer is in sleep mode.
1. Sleep Indicator Light location
2. Ambient Light Sensor location
The results were that the pulsing light would be brighter in a well lit room and much softer in a dark room.
ALS Controls for Display and Keyboard
Controls for ALS are found in the Display and Keyboard System Preferences.
Follow these steps to turn the automatic display brightness feature on or off:
From the Apple menu, choose System Preferences.
From the View menu, choose Displays.
Click the "Automatically adjust brightness as ambient light changes" checkbox.
Follow these steps to turn the automatic keyboard brightness feature on or off:
1. From the Apple menu, choose System Preferences.
2. From the View menu, choose Keyboard.
3. Click the "Illuminate keyboard in low light conditions" checkbox.
You can also turn on or off the keyboard illumination feature by pressing the F8 key.
NOTE: If you see function keys as shown here on a portable Mac computer, it has a backlit keyboard.
These keys only respond in this way when the ALS is turned on. If you press the keyboard illumination
control keys (F8, F9 and F10) and you see a dimmed graphic with the prohibitory sign (see below), the sensed
ambient light is not low enough for the keyboard illumination to work.
ALS Troubleshooting
Determining if ALS is functioning properly cannot be done in a well lit room.
To see if a keyboard is backlit, you should examine the computer in a dark room. Attempting to block
the ALS sensors manually does not work well.
Troubleshooting and Repair Significance
You know to verify backlit keyboard issues in a darkened room.
You know where to find ALS controls on both the keyboard and System Preferences.
Back to top
Next: Compression
How Compression Works
Troubleshooting and Repair Significance
With the widespread use of digital media with files sizes exceeding the gigabyte range, there is a growing
need to make files smaller without damaging their usefulness.
Users distribute such content more frequently and have an ongoing need to store large files efficiently.
How Compression Works
At a very basic level, all compression schemes work to eliminate redundant information from a file.,
File compression routines write the redundant information once and then refer back to this information
whenever it appears in the file.
This reuse of information enables compression utilities to create smaller files from larger originals.
Compression utilities come in two major types, lossy and lossless.
Lossy Compression
Lossy compression removes some non-redundant content from the original. This results in reduced quality of
the compressed file. Audio will not possess the same fidelity. Digital images will not have as much detail.
Lossy Compression Formats
Here are examples of lossy compression formats:
JPEG (Joint Photographic Experts Group)
This is a standard for the data compression of still pictures. JPEG is recommended when exporting a
still image from a DV clip if the intent is to send the picture through email or use it on the World Wide
MP3 (MPEG layer 3)
A popular format for compressing music.
An ISO standard based on the QuickTime file format that defines multimedia file and compression
Lossless Compression
Lossless compression allows the exact original data to be rebuilt from the compressed file.
Lossless Compression Formats
Here are examples of lossless compression formats:
This is the format used when archiving material in Mac OS X.
GIF (Graphic Interchange Format)
A lossless 8-bit (256 colors) RGB image format often used for Web images.
PNG (Portable Network Graphics)
A bit-mapped image format used for screenshot captures in the Mac OS.
TIFF (Tagged Image File Format)
A high quality format often used in publishing.
AIFF (Audio Interchange File Format)
Developed by Apple and used for storing sound data on computers.
ALAC (Apple Lossless Audio Codec)
Created by Apple and used for lossless compression of digital music.
Troubleshooting and Repair Significance
Knowing the difference between lossy and lossless compression routines allows you to address issues
of file degradation without wasting time on problems created by a compression utility.
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Next: CUPS
CUPS Overview
CUPS in Mac OS X
Troubleshooting and Repair Significance
CUPS Overview
CUPS (Common UNIX Printing System) is a cross-platform, portable printing software layer for UNIXbased operating systems. It is owned and maintained by Apple to promote a standard printing solution. It is
the standard printing system used in Mac OS X v10.2 and later.
CUPS uses the Internet Printing Protocol ("IPP") as the basis for managing print jobs and queues and adds
network printer browsing and PostScript Printer Description ("PPD") based printing options to support realworld printing.
CUPS uses several industry-standard protocols, including:
Internet Printing Protocol (IPP)
Line Printer Daemon (LPD)
Postscript Printer Description (PPD)
Server Message Block (SMB)
AppSocket (JetDirect)
More information on CUPS is available at
More information on IPP is available at
CUPS configuration files are located in the hidden path: /private/etc/cups/.
CUPS in Mac OS X
When you use Mac OS X Print and Fax System Preferences to set up a printer, you are relying on CUPS for
interaction with various printing services.
If you turn on Printer Sharing in System Preferences Sharing pane, you can then access CUPS on your
computer using Safari (or another Web browser).
Type the address "http://localhost:631" into the browser's address field:
If you select Manage Printers, you will be able to see the printers
Troubleshooting and Repair Significance
When troubleshooting printing issues, CUPS access can provide useful information.
Back to top
Next: Open Firmware
Open Firmware
Open Firmware Access
Open Firmware Password Protection
What Open Firmware Password Protection Does
Lost Firmware Password
Troubleshooting and Repair Significance
Open Firmware is a small program contained on a chip within a PowerPC Mac that controls its boot process.
It is responsible, among other things, for building the device tree and probing the expansion slots for I/O
The Open Firmware environment does not rely on the Mac OS.
Open Firmware Access
You can start up into Open Firmware by holding down the Command-Option-O-F keys at restart or power on
before any video is displayed on the screen.
This enables you to manipulate the computer via command line instructions without relying on the Mac OS.
Open Firmware Password Protection
It is possible to password protect a PowerPC Mac at a low level using Open Firmware Password Protection.
To maximize the effectiveness of the firmware password, do all of the following:
Use a secure password that contains both numerals and letters in the first eight characters.
In the Users control panel, Accounts pane of System Preferences, or Server Admin application
(whichever applies to your Mac), strictly limit Admin user status to trusted personnel.
Restrict physical access to the computer.
Select the Mac OS X System folder for the startup device that you plan to protect.
If startup device is correctly selected, select it in Startup Disk preferences and close the preference
If you receive a “save changes” dialog, saving the changes secures your startup device.
IMPORTANT: If you reset the PRAM or Open Firmware, you need to reselect your startup device prior to
resetting the Open Firmware Password.
WARNING: The Open Firmware Password can be reset and changed by any one of the following:
By any administrator user, as designated in the Accounts preferences (or in Server Admin).
Via physical access to the inside of the computer.
When the computer is started up in Mac OS 9 (where applicable)
How to enable the Open Firmware Password
On any computer capable of firmware password protection (including Intel-based Mac computers), follow
these steps:
For Mac OS X 10.1 to 10.3.9, download and install the Open Firmware Password application, which
you can get here.
For Mac OS X 10.4 or later, you must use the updated version that can be copied from the software
installation disc (located at /Applications/Utilities/ on the disc).
Open the Open Firmware Password application.
Click the icon to authenticate. Enter an administrator username and password when prompted.
Click Change.
Click to select the checkbox for "Require password to change Open Firmware settings", as shown
Type your password in the Password and Verify fields.
Click OK. A confirmation appears.
Click lock icon to prevent further changes.
Choose Quit from the Open Firmware Password application menu.
What Open Firmware Password Protection Does
When turned on in most PowerPC computers, Open Firmware Password Protection:
Blocks the ability to use the "C" key to start up from an optical disc.
Blocks the ability to use the "N" key to start up from a NetBoot server.
Blocks the ability to use the "T" key to start up in Target Disk Mode (on computers that offer this
Blocks the ability to start up in Verbose mode by pressing the Command-V key combination during
Block the ability to start up a computer in Single-user mode by pressing the Command-S key
combination during startup.
Blocks a reset of Parameter RAM (PRAM) by pressing the Command-Option-P-R key combination
during startup.
Requires the password to use the Startup Manager, accessed by pressing the Option key during startup.
Requires the password to enter commands after starting up in Open Firmware, which is done by
pressing the Command-Option-O-F key combination during startup.
Lost Firmware Password
If the Firmware password is lost, follow these steps. This procedure works on both PowerPC and Intel-based
Mac computers.
Important: ESD Precautions — To avoid damaging components, be sure to follow Electrostatic Discharge
(ESD)-safe repair practices.
1. Shut down the computer.
2. Gain access to the computer's RAM slots.
3. Add or remove a RAM DIMM to change the total amount of installed RAM. For example:
If the computer has two RAM DIMMs (128 MB DIMM and 64 MB DIMM) for a total of 192 MB of
memory, remove the 64 MB DIMM. This changes the total memory of the computer to 128 MB RAM.
If the computer has a single RAM DIMM, you can change the total memory by adding a DIMM of any
compatible size.
NOTE: Removing a computer's only DIMM is not an option and will prevent the computer from
starting up.
4. Turn on the computer and immediately reset PRAM by holding the Command-Option-P-R key
combination. Press the keys until you've heard two successive startup sounds.
5. Open Firmware password protection is now disabled. Shut down the computer and return it to its
original RAM configuration.
Troubleshooting and Repair Significance
You can start up a PowerPC computer in the Open Firmware environment.
You have seen some of the key commands that you can use during startup.
You can enable Open Firmware password protection.
You have reviewed what this form of password protection provides.
You can bypass Open Firmware password protection when necessary.
Back to top
Next: EFI
Extensible Firmware Interface (EFI)
About Extensible Firmware Interface
Useful Knowledge about EFI
EFI Password Protection
Troubleshooting and Repair Significance
About Extensible Firmware Interface
The Intel EFI specification defines the interface between the OS and the Mac computer’s firmware. A good
way to think about EFI is that it's the equivalent to Open Firmware for Intel-based Mac computers.
The interface consists of data tables that contain platform-related information, plus boot and runtime service
calls that are available to the operating system and its loader. Together, these provide a standard environment
for booting an operating system and running pre-boot applications
Useful Knowledge about EFI
Intel-based Mac computers do not use standard PC BIOS (Basic Input/Output System). EFI provides
this functionality.
EFI builds a table of the computer's hardware configuration automatically and passes that list of device
information to the operating system without any user interaction.
There is no user interface to the EFI environment as there was with Open Firmware.
EFI Password Protection
You can easily password-protect EFI in Intel-based Mac computers using an included utility that comes with
Mac OS X. You can also use this utility to remove EFI password protection. However, just as with PowerPCbased Mac computers, if you forget your firmware password you will need to go through the steps outlined in
the previous section to clear this password.
NOTE: Password protection cannot be removed from some Mac computers such as MacBook Air with its
fixed amount of memory. Please use caution when applying firmware passwords on such models.
Troubleshooting and Repair Significance
While you cannot access EFI directly, awareness of its functions as they apply to diagnostics and
startup key commands is very useful. EFI based diagnostics do not use any OS components. Some
startup key commands for Intel-based Mac computers such as "D for Diagnostic" involve EFI.
Back to top
Next: MIDI
Troubleshooting and Repair Significance
Musical Instrument Digital Interface (MIDI) enables music-related devices to communicate with each other
and with Mac desktops and portables over a serial interface.
This is done either directly via USB, or via MIDI cables and connectors which require a separate USB to
MIDI adapter.
MIDI communication doesn't carry the music itself.
Instead, it carries instructions, such as what instrument or sound to play and when to play it.
MIDI assigns each musical device a unique numeric address, so applications can send instructions to each
device independently.
For instance, an application that orchestrates music can send the instructions for the drum part to a drum
machine, the brass and woodwind parts to a keyboard, and the string parts to a sampler.
Mac OS X includes frameworks or resources to support MIDI in the /System/ Library/Frameworks directory.
Audio MIDI Setup can discover MIDI devices that are attached to the computer and display them in its
window, where you can then establish links (and hierarchical links) between devices.
Troubleshooting and Repair Significance
While MIDI is not normally part of standard troubleshooting, we are providing this overview as context for
troubleshooting some connectivity issues.
Back to top
Next: Optical Drives
Optical Drives
Optical Drives Introduction
CD-ROM Drives
CD-RW Drives
Combo Drives
Dual Layer DVDs
Double Layer Drives
Further Reading
Handling Optical Drives
Troubleshooting and Repair Significance
Optical Drives Introduction
Most Mac computers have some sort of optical disc drive used for reading data discs, playing audio discs,
viewing DVD discs, or burning discs of all types.
The exact capabilities depend on the type of drive installed in the Mac.
CD-ROM Drives
The most basic optical disc drive is a CD-ROM (Compact Disk-Read Only Memory) drive capable of reading
data and audio previously recorded on 650 megabyte (MB) discs.
CD-RW Drives
A CD-RW (Compact Disk Rewritable) drive can read, write, and rewrite recordable CDs. A CD-RW drive
can write (or “burn”) a CD-R ( Compact Disk Recordable) disc, which is permanent, or it can write a CD-RW
disc, which can be erased and written on again.
NOTE:The current Apple disc-burning software (such as, the Burn command in the Finder) writes to media
only once—it doesn't support rewriting, even on CD-RW media. Multiple rewrites require a Disk Utility erase
Combo Drives
A combo drive is a CD-RW/DVD, and therefore can be used to play videos and read data written on DVD
A SuperDrive has all of the functionality of a Combo drive, with the addition of the ability to burn data or
video to DVD-R and DVD-RW discs. The Apple software for creating DVD movie discs, called iDVD,
comes with the SuperDrive and is available as part of the iLife package.
There are two different and incompatible DVD burning formats in wide use within computers today:
DVD-R / DVD-RW and
There exist both types of media and drive mechanisms that can work with either or both types.
Up until recently, Apple used only DVD-R / DVD-RW compatible drive mechanisms in its products, and
supported only DVD-R and DVD-RW disc types.
With the introduction of the Mac mini model with an optional DVD+/-RW/CD-RW SuperDrive, Apple now
supports recordable DVD discs of both + and - types.
Dual Layer DVDs
Beginning with the iMac G5 (Ambient Light Sensor), all SuperDrives come equipped to burn dual-layer
DVD discs.
The additional storage capacity of the DVD+R disc enables you to record 4 hours of DVD-quality video or 16
hours of VHS-quality video without turning over the disc.
You can also archive up to 8.5 GB of computer files on one dual-layer DVD+R disc. This is almost twice the
capacity of traditional single-layer DVD+R discs (4.7 GB).
Disc label
Polycarbonate layer
Metal reflector
Dye-recording layer 2
Semi-transparent metal reflector
Dye-recording layer 1
Polycarbonate layer
Laser beam writing to each layer
The dual-layer DVD+R specification does not require the entire disc to be recorded. However, if one layer of
a dual-layer DVD+R has a recorded signal at a particular point on the disc, the other layer must have a
matching signal. Otherwise, a DVD player may detect an error.
In other words, if one layer has 3 GB of data recorded, the other layer must also have 3 GB recorded. Blank
space may be left at the edge of the DVD without any playback problems.
This is automatically handled by the SuperDrive.
The double-layer SuperDrive only supports burning to DVD+R dual-layer media. It does NOT burn to DVDR dual-layer discs but can read data from them.
The double-layer SuperDrive can burn standard 4.7 GB DVD-R discs, but not the 8.5 GB dual-layer DVD-R
Double-Layer Drives
The 16x SuperDrive built into the latest Mac Pro supports double-layer (DVD±R DL) discs. While singlelayer DVD discs hold up to 4.7GB of data, double-layer discs have two layers, allowing the SuperDrive laser
to read from and write to both layers, almost doubling the storage capacity to 8.5GB. Here is a break-out of
the formats the later versions of this drive can record to and play:
Media Type
Write Speeds
18x, 8x, 4x, 2x, 1x, single-layer, depending on media
8x, 6, 4x, 2.4x, double-layer, depending on media
16x DVD5
12x DVD9
6x, 4x, 2x, 1x, depending on media
8x, 4x, 2.4x depending on media
24x (high speed media)
Further Reading
HT2543 About optical disc drive burning and write speeds
HT2882 Factors that affect writing to or reading from optical media
Handling Optical Drives
Optical drives installed in the latest Mac computers require fairly delicate handling. The following are
guidelines that should be followed whenever such drives are removed or replaced:
Observe ESD (electrostatic discharge) guidelines when handling optical drives.
Handle the drive only by the sides and back edge.
Do not touch the front of the drive.
Do not press on the drive or lift it by the top and bottom cover.
Do not handle the drive by the gull wing edge only.
When storing optical drives, use approved packaging boxes. Never stack loose drives.
When returning a defective optical drive, use the original packaging and an antistatic bag.
Pack only one drive per box.
Troubleshooting and Repair Significance
You can describe disc format capabilities
You can describe recording and playback formats that are used on newer Mac computers
You know how to correctly handle optical drives
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Next: QuickTime
QuickTime Overview
Troubleshooting and Repair Significance
QuickTime Overview
QuickTime Player
QuickTime Player is a free multimedia player used to play and view video, audio, still images, graphics, and
virtual reality (VR) movies.
QuickTime supports the most popular formats on the Internet for news, sports, education, movie trailers, and
other entertainment.
Multimedia Architecture
QuickTime is also a multimedia architecture that other applications can leverage.
Apple’s iTunes, iMovie, and third-party programs use the QuickTime architecture for key multimedia
QuickTime can access 200 kinds of digital media with a Mac or PC including images, music, MIDI, and
QuickTime Pro
QuickTime Pro is an upgraded version of QuickTime Player with advanced features including editing
capabilities and multiple export options.
NOTE: Mac OS X v10.6 Snow Leopard includes QuickTime X which comes with a new QuickTime Player,
offering a clean and uncluttered interface, easy media sharing, and flexible recording capabilities.
A Snow Leopard-compatible version of QuickTime Player 7 is also available for use with older media or with
existing AppleScript-based workflows.
QuickTime Player 7 can be used to playback formats such as QTVR, interactive QuickTime Movies, and
MIDI files. Also, it supports QuickTime 7 Pro registration codes for access to QuickTime Pro functionality.
Troubleshooting and Repair Significance
Understanding that QuickTime comprises an architecture, a player, and an editing environment will
prevent confusion when addressing media-related troubleshooting issues.
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Next: Rosetta
What is Rosetta?
How Rosetta Works
Compatibility with Rosetta
Forcing an Application to Run Translated
Plug-Ins and Rosetta
Device Drivers and Rosetta
Troubleshooting and Repair Significance
What is Rosetta?
Rosetta (named for the Rosetta Stone) is a Mac OS X technology that lets an application written for a
PowerPC Mac run on an Intel-based Mac.
Rosetta runs automatically and transparently and allows applications to run as non-native binaries. The
majority of Mac OS X applications for PowerPC-based Mac computers can run on an Intel-based Mac
using Rosetta.
Rosetta translates PowerPC code into Intel code. It does not emulate a PowerPC processor or
If an application is said to be "running translated" on an Intel-based Mac, it is using Rosetta and most likely is
a PowerPC application or universal binary application forced to run translated.
How Rosetta Works
With the two Mac platforms (PowerPC and Intel), when you launch an application on an Intel-based Mac, the
Mac OS X kernel needs to determine the type of the application at launch.
There are three general application types:
Native (compiled to run on Intel-based Mac computers: includes universal binary applications)
Non-native (compiled to run only on PowerPC-based Mac computers: not designed for Intel-based
Mac computers)
Incompatible (covered later in this training)
A native binary application will simply launch on an Intel-based Mac and operate like a standard Mac OS X
If the application is not native, the Mac OS X kernel launches the application using Rosetta.
Incompatible applications do not launch and may give you an error dialog.
Behind the scenes, Rosetta is looking at the non-native (PowerPC) code that the application is trying to
execute and translates that code so the Intel processor can use it, as represented below:
Notes on Rosetta
Rosetta doesn't simulate or emulate the entire PowerPC processor environment.
Rosetta doesn't run as a separate process or thread.
Rosetta launches within the non-native application's process and optimizes this translated code to
deliver the best possible performance on the non-native application.
Rosetta is also very smart at caching frequently used calls and code from the non-native (PowerPC)
application. Code that is reused repeatedly in your application benefits the most because it needs to be
translated only once, and has already been optimized.
Compatibility with Rosetta
An application's compatibility with Rosetta depends on the application type.
A word processor, which has a lot of user interaction and low computational needs, is typically very
However, Rosetta does NOT run the following types of PowerPC Mac OS X applications:
Applications built for any version of the Mac OS earlier than Mac OS X (Mac OS 9, Mac OS 8, Mac
OS 7, and so on)
The Classic environment
Code written specifically for the Velocity Engine (AltiVec technology)
Code that inserts preferences in the System Preferences window
Applications that require a G4 or G5 processor
Applications that depend on one or more PowerPC-only kernel extensions
Kernel extensions (drivers or code that directly communicate with the computer's hardware).
Java applications with JNI libraries
Java applets in applications that Rosetta can translate (this means a web browser that Rosetta can run
translated will not be able to load Java applets)
Remember, Rosetta is a Mac-to-Mac translation process that allows you to use PowerPC-based applications
on your Intel-based Mac and does not provide any Windows or other operating system compatibility features.
NOTE: With the introduction of Mac OS X v10.6 (Snow Leopard) Rosetta is only installed under the
following conditions:
1. The user specifically selects to install it as part of a 'custom' install of Snow Leopard.
2. The user attempts to launch a PowerPC application and Rosetta isn't already installed. In this case,
Snow Leopard recognizes this and offers to download and install Rosetta 'on-demand'.
Forcing an Application to Run Translated
On an Intel-based Mac you can manually force a universal binary application to run using Rosetta by
selecting the "Open using Rosetta" checkbox in the application's Info window:
With "Open using Rosetta" selected, when the application is launched, it runs translated on the Intel-based
Plug-ins and Rosetta
When a universal binary application uses external programming (in the form of plug-in modules or add-on
modules), it is important to make sure those installed plug-ins are universal binaries as well.
For example, If you install a PowerPC version of the Macromedia Flash plug-in on an Intel-based Mac, you
will get a message saying that plug-in is not installed.
To let that plug-in work correctly, you have to launch Safari translated on the Intel-based Mac so that Rosettacompatible plug-ins can operate correctly
Intel binaries (not universal binaries) cannot run translated. When you need to run a application translated,
you have to use a universal binary or PowerPC version.
Device Drivers and Rosetta
The same rules apply for printer and other device drivers that may use plug-ins:
Nearly every printer driver that shipped with Mac OS X 10.4 is included in Mac OS X for Intel as a universal
PPC printer drivers should run in Rosetta but check with the third-party vendor for a universal binary version
of the driver/plug-in for scanners etc.
Troubleshooting and Repair Significance
In some situations, forcing a Rosetta launch for an application can solve a customer issue.
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Next: Sudden Motion Sensor
Sudden Motion Sensor (SMS)
What It Is
System Profiler
Troubleshooting and Repair Significance
What It Is
Sudden Motion Sensor technology is built-in protection for the hard disk, designed to help prevent disk
failures if the computer is dropped or undergoes unusually strong vibration.
The Sudden Motion Sensor is designed to detect unusually strong vibrations. If this happens, the SMS
instantly parks the hard drive heads to help reduce the risk of damage to the hard drive on impact.
When stable again, SMS unlocks the hard drive heads, and the Mac is up and running within seconds.
The Sudden Motion Sensor does not prevent hard drive failures. Its primarily function is to prepare the hard
drive for impact.
When the Mac is sleeping, the Sudden Motion Sensor is not active - the hard drive heads are already parked
but damage can still be sustained.
The Sudden Motion Sensor is enabled by default.
No user adjustment, or off/on function is available in the Mac OS X interface - though Terminal commands to
disable it are listed below.
System Profiler
The Sudden Motion Sensor's state can be determined by looking at System Profiler under Hardware
Sudden Motion Sensor
This field either says Enabled or Disabled.
The System Profiler shows the Sudden Motion Sensor as Disabled under two conditions:
If a continuous stream of interrupt signals is generated by the module (for example, if there is a motion
sensor failure) the computer automatically disables the feature.
The feature is disabled through a command line, issued via the Terminal utility. In this case, until
another command line is executed, the Sudden Motion Sensor remains off.
There is no graphical user interface for the Sudden Motion Sensor, but you can type a command in the
Terminal application to disable or enable it:
To disable:
Launch the Terminal application (found in the Utilities folder).
You need the system password to perform this command.
At the command line, enter the command:
sudo pmset -a sms 0
To enable:
Launch the Terminal application (found in the Utilities folder).
You need the system password to perform this command.
At the command line, enter the command:
sudo pmset -a sms 1
Use System Profiler to verify that the Sudden Motion Sensor has been either disabled or enabled.
NOTE: In almost all situations, if you need to turn off the Sudden Motion Sensor technology, you are
probably using the Apple portable in an unsafe environment.
If the System Profiler states the Sudden Motion Sensor is disabled when it should not be:
1. Put the Mac to sleep.
2. Pick the computer up and put it back on a steady table top.
3. Wake the Mac up, refresh the System Profiler window under View menu (or use Command-R). If it
changes states to Enabled, try a few more sleep/wake/refresh cycles to verify it is working correctly.
4. If the Mac is still reporting Disabled, launch the Terminal application (found in the Utilities folder).
5. You need the system password to perform this command.
At the command line, enter the command:
sudo pmset -a sms 1
6. Now, refresh System Profiler and check if it is enabled.
7. If System Profiler still reports that the Sudden Motion Sensor is Disabled, there is a problem with the
Sudden Motion Sensor. The Apple portable needs to be serviced.
Troubleshooting and Repair Significance
You can determine Sudden Motion Sensor status on a Mac
You can reset Sudden Motion Sensor status
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Next: Universal Binaries
Universal Binaries
Identifying Application Types
Troubleshooting and Repair Significance
There are two types of usable applications on an Intel-based Mac:
Native (compiled for Intel)
Non-native (compiled for PowerPC and requires Rosetta to operate):
An additional type runs natively on both PowerPC and Intel-based Mac computers.
That means it contains code for both processor types.
This is the universal binary.
A universal binary application is created by a developer who modifies and recompiles an application so it
runs natively on either a PowerPC-based or Intel-based Mac.
If launched on an Intel-based Mac it won't use Rosetta.
Apple has released this icon for third-party application developers to use to indicate an application is a
universal binary:
Identifying Application Types
You can tell if an application is a universal binary by looking at the Kind field in the General section of the
Info window for the application.
Depending on the type, you should see:
Troubleshooting and Repair Significance
Identifying whether an application will run on PowerPC or Intel-based Mac computers will enable you
to avoid troubleshooting non-existent issues.
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Next: Exercise Answer Key
Next: This concludes the Underlying Technologies course.
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