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Overview of iMac Developer Note

This chapter provides an overview of the hardware and software features of the current models of the iMac computer.

New Features

New features are listed here with links to the sections that describe them. For a comparison of 15” and 17” iMac features, see Table 1-1.

Processor and speed: The microprocessor in the iMac computer is a PowerPC G4 with a clock speed of 1 GHz in the 15” configuration and 1.25 GHz in the 17” configuration. For more information, see PowerPC G4 Microprocessor.
Memory: The computer comes with 256 MB of DDR333 SDRAM installed in an internal 184-pin DIMM expansion slot, with a build-to-order option of 512 MB. A second user-accessible slot accepts an SO-DIMM up to 512 MB. The maximum supported memory is 1 GB. For more information, see System RAM.
USB 2.0 ports The computer has three USB 2.0 ports; see USB Interface.
System bus: The speed of the system bus is 167 MHz. For more information, see Memory and I/O Device Controller.
Graphics acceleration: The AGP 4X graphics IC used in the iMac is an nVidia GeForce4 MX in the 15” configuration and an nVidia GeForce FX 5200 Ultra in the 17” configuration. For more information, see Video Display Subsystem.
External video port: The external display connector supports VGA, composite and S-video formats for devices such as monitors, projectors, and television sets. This is a new feature in the 15” configuration. The Apple VGA adapter is available to connect with a VGA display. A video adapter with composite and S-video connectors is available separately. For more information, see Video Monitor Port.
AirPort Extreme (optional): A 54 Mbps AirPort Extreme Card is available as a build-to-order option or as a user-installable upgrade. This is a new feature in the 15” configuration. For more information, see AirPort Extreme Wireless Support.
Bluetooth (optional): Bluetooth is available as a build-to-order option to enable short-range wireless connections between desktop and laptop computers and a host of other peripheral devices. This is a new feature in the 15” configuration. For more information, see Bluetooth Technology.

Feature Set

Here is a complete list of the features of the iMac computer. Each feature is described in more detail in a later section.

Processor and speed: The microprocessor in the iMac computer is a PowerPC G4 with a clock speed of 1 GHz in the 15” configuration and 1.25 GHz in the 17” configuration. For more information, see PowerPC G4 Microprocessor.
Cache: The backside 256 KB L2 cache is included on the microprocessor IC and has the same clock speed as the microprocessor. For more information, see Level 2 Cache.
Memory: The computer comes with 256 MB of DDR333 SDRAM installed in an internal 184-pin DIMM expansion slot, with a build-to-order option of 512 MB. A second user-accessible slot accepts an SO-DIMM with up to 512 MB. The maximum supported memory is 1 GB. For more information, see System RAM.
Hard disk storage: The built-in hard disk is 7200 rpm with a capacity of 80 GB and a 160 GB build to order option. For more information, see Hard Disk Drive.
SuperDrive: The 17” configuration of the iMac has a SuperDrive (CD-RW/DVD-R). For more information, see SuperDrive (CD-RW/DVD-R).
Combo drive: The 15” configuration of the iMac has a combination CD-RW/DVD-ROM drive. For more information, see Combo (CD-RW/DVD-ROM) Drive.
Display: The iMac has a built-in 17-inch widescreen flat-panel or 15-inch flat-panel display (measured diagonally). For more information, see Flat Panel Display.
USB 2.0 ports The computer has three USB 2.0 ports; see USB Interface.
System bus: The speed of the system bus is 167 MHz. For more information, see Memory and I/O Device Controller.
Graphics acceleration: The AGP 4X graphics IC used in the iMac is an nVidia GeForce4 MX in the 15” configuration and an nVidia GeForce FX 5200 Ultra in the 17” configuration. For more information, see Video Display Subsystem.
Video RAM: The video hardware in the iMac includes 32 MB (15” configuration) or 64 MB (17” configuration) of DDR SDRAM, which supports 3D features and millions of colors in all resolutions. For more information, see Video Display Subsystem.
External video port: The external display connector supports VGA, composite and S-video formats for devices such as monitors, projectors, and television sets. The Apple VGA adapter is available to connect with a VGA display. A video adapter with composite and S-video connectors is available separately. For more information, see Video Monitor Port.
FireWire 400 ports: The iMac computer has two IEEE-1394a FireWire 400 ports, which support transfer rates of 100, 200, and 400 Mbps. For more information, see FireWire 400 Connector.
Target disk mode: The computer can be configured like a FireWire storage device connected to another computer. See Target Disk Mode.
Modem: The iMac has a built-in V.92 modem with a 56 Kbps data rate. For more information, see Internal Modem.
Ethernet: The iMac has a built in Ethernet port for a 10Base-T and 100Base-TX operation. For more information, see Ethernet Port.
AirPort Extreme (optional): A 54 Mbps AirPort Extreme Card is available as a build-to-order option or as a user-installable upgrade. This is a new feature in the 15” configuration. For more information, see AirPort Extreme Wireless Support.
Bluetooth (optional): Fully-integrated Bluetooth is available as a build-to-order option to enable short-range wireless connections between desktop and laptop computers and a host of other peripheral devices. This is a new feature in the 15” configuration. For more information, see Bluetooth Technology.
Sound: The iMac computer includes external Apple Pro Speakers, a built-in speaker and microphone, stereo headphone jack, Apple Speaker minijack, and audio line-in. For more information, see Sound System.
Keyboard: The iMac comes with an Apple Keyboard. The keyboard is also a USB hub with two USB 1.1 ports. For more information, see Keyboard Features.
Mouse: The iMac comes with an Apple Mouse, a USB mouse with optical tracking. For more information, see Mouse.

Comparison of 15” and 17” iMac Features

Table 1-1 provides a quick comparison of the features of the two configurations of the iMac computer.

**Table 1-1** Feature comparison
	15” iMac	17” iMac
CPU and speed	PowerPC G4 1 GHz	PowerPC G4 1.25 GHz
System bus speed	167 MHz	167 MHz
Main memory	256 MB, 333 MHz DDR SDRAM, supports expansion up to 1 GB	256 MB, 333 MHz DDR SDRAM, supports expansion up to 1 GB
Display	Built-in 15-inch flat panel	Built-in 17-inch, widescreen flat panel
Graphics IC	nVidia GeForce4 MX	nVidia GeForce FX 5200 Ultra
Graphics memory	32 MB DDR RAM	64 MB DDR RAM
Hard disk drive	80 GB Ultra ATA-100 7200 rpm	80 GB Ultra ATA-100 7200 rpm
Optical drive	Tray-load Combo drive	Tray-load SuperDrive
External monitor port	VGA output port/S-video and composite video output	VGA output port/S-video and composite video output
Data ports	Three external USB 2.0 ports plus two USB 1.1 ports on keyboard; two FireWire 400 ports	Three external USB 2.0 ports plus two USB 1.1 ports on keyboard; two FireWire 400 ports
Communication features	10/100 Ethernet; 56K V.92 fax modem	10/100 Ethernet; 56K V.92 fax modem
Wireless features	Optional 54 Mbps AirPort Extreme Card; optional internal Bluetooth	Optional 54 Mbps AirPort Extreme Card; optional internal Bluetooth
Sound features	Built-in speaker and microphone; stereo headphone jack and Apple Pro Speaker minijack; external Apple Pro speakers, audio line-in	Built-in speaker and microphone; stereo headphone jack and Apple Pro Speaker minijack; external Apple Pro speakers, audio line-in

System Software

The iMac computer comes with Mac OS X version 10.2.7 or later installed. Mac OS 9 applications can be run in Classic mode. For more information about Mac OS X, see the reference listed in Mac OS X.

Machine Identification

Apple Computer discourages the targeting of code to specific machine models. However, if it is necessary to identify a machine in order to determine the features of the machine, applications can use the IORegistry with Mac OS X. Or, in many cases, it is feasible to use Gestalt calls to test a machine for specific features.

Asset management software that reports the kind of machine it is run on can obtain the value of the property at Devices:device-tree:compatible in the Name Registry. The model string is the first program-usable string in the array of C strings in the compatible field. The value of the string in the compatible property is PowerMac6,1.

The string obtained from the compatible property cannot be displayed to the computer user. If it is available, use the result from calling Gestalt ('mnam', &result) where result is a string pointer. This call returns a Pascal style string that can be displayed to the user.

Velocity Engine Acceleration

The Velocity Engine (an implementation of AltiVec) is the vector processing unit in the PowerPC G4 microprocessor. Some system software has been modified to take advantage of the accelerated processing that the Velocity Engine makes possible. System software has also been modified to support low-level operations using the Velocity Engine.

For complete information on the Velocity Engine, refer to the following Apple website:

http://developer.apple.com/hardwaredrivers/ve/index.html

For more information, please see the references at Velocity Engine.

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