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

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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.

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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 b) Cannot boot up c) Screen too dim to read on airplane d) Remote can’t turn on Apple TV

1. Ambient Light Sensor

2. Infrared

3. Rosetta

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:

Maximum Speed

Parallel ATA

1.33 Gb/s (133 MB/s)

Maximum Cable Length 0.45 meters

Hot Pluggable


Maximum Drives per


Signaling Voltages


5 V

Serial ATA

1.5 Gb/s (150 MB/s)

1.0 meter



0.25 V

Pins per Channel

40 7

* 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 performance.

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.

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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 transmissions.


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 segment.

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.

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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 include:

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 connection.

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 consumption

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 resistance.

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 trash.

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.

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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 FireWire 800

IEEE 1394a Standard

Up to 400 Megabits per second

IEEE 1394b Standard

Up to 800 Megabits per second supports 4-pin and six-pin connectors 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 newer.

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 code.

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 mode".

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.

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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.

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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.

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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 down.

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 casing.

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 here:

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.

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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.

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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 lengths.

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.

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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 video

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.

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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)

1. If the computer is on, turn it off.

2. Disconnect the AC power adapter.

3. Remove the battery.

4. 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.

5. Wait 5 seconds.

6. Reconnect the AC power adapter.

7. Put the battery back in the computer.

8. 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.

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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 formats.

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.

Next: Open Firmware

Back to top

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 devices.

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 pane.

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 below.

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 startup.

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.

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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 beforehand.

Combo Drives

A combo drive is a CD-RW/DVD, and therefore can be used to play videos and read data written on DVD media.


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).

1. Disc label

2. Polycarbonate layer

3. Metal reflector

4. Dye-recording layer 2

5. Spacer

6. Semi-transparent metal reflector

7. Dye-recording layer 1

8. Polycarbonate layer

9. 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 DVD-

R 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 discs.

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



DVD±R 18x


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









CD-ROM 32x -

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

Back to top

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 functions.

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 environment.

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 application.

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 compatible.

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 binary.

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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