Retired Document
Important: This document may not represent best practices for current development. Links to downloads and other resources may no longer be valid.
Overview of Power Mac G4
The desktop Power Mac G4 computer uses dual PowerPC G4 microprocessors and is intended for use in content creation, desktop publishing, multimedia, and other activities that require high performance.
New Features
Here is a list of the features that are new to the Power Mac G4 computer.
Microprocessor clock speed The clock frequency is dual 867 MHz, 1 GHz, or 1.25 GHz. For more information, see PowerPC G4 Microprocessor.
System bus speed The system bus has a clock speed of 133 MHz or 167 MHz. For more information, see Processor Bus.
DDR SDRAM Four DIMM slots for 184 pin, 133 MHz or 167 MHz DIMMs (dual inline memory modules) using DDR (double data rate) SDRAM devices. A minimum of 256 MB of RAM is installed in one of the slots. For more information, see Main Memory Bus.
Graphics card Three graphics cards are available: NVidia GeForce4 MX, ATI Radeon 9000 Pro, and NVidia GeForce4 Titanium (as an enhancement option). All cards have ADC and DVI connectors. For more information, see Graphics Cards.
Hard disks An internal Ultra ATA /100 hard disk occupies one of four drive bays in the bottom of the computer and functions as the default boot disk. Space is available in that bay for an auxiliary Ultra ATA /100 device. An internal Ultra ATA /66 device supports two more drives. For more information, see Fixed-Media Drives.
Disk drives Two bays for storage devices with removable-media access through the front panel. For more information, see Disk Drives.
Headphone jack The redesigned front panel includes a headphone jack. For more information, see Headphone Jack.
Audio line-in Rear panel audio line-in port for self-powered microphones or other audio equipment. For more information, see Audio Input Jack.
Audio line-out Rear panel audio line-out port for externally-powered speakers or other audio devices. For more information, see Audio Output Jack.
Switches The programmer’s switch and reset button on the rear panel have been removed. For more information, see the below URL for the AppleCare Knowledge Base Article ID: 88330.
Hardware Features Summary
Here is a list of the hardware features of the Power Mac G4 computer. The major features are described more fully later in this note.
Microprocessors Dual PowerPC G4 microprocessors running at a clock frequency of 867 MHz, 1 GHz, or 1.25 GHz. For more information, see PowerPC G4 Microprocessor.
Dual processor configuration The Power Mac G4 computer has a dual-processor configuration. For information about software and multiprocessing, see Dual Processors and Mac OS 9 Applications.
Memory caches The PowerPC G4 microprocessors used in the Power Mac G4 computer have an internal 256 KB level 2 cache. The computer also has an external 1 or 2 MB level 3 cache. For more information, see Cache Memory.
Processor system bus The bus has 64-bit wide data and 32-bit wide address, a 133 or 167 MHz clock, and supports MaxBus protocol. For more information, see Processor Bus.
DDR SDRAM Four DIMM slots for 184 pin DIMMs (dual inline memory modules) using DDR (double data rate) SDRAM devices. A minimum of 256 MB of RAM is installed in one of the slots. For more information, see RAM Expansion.
ROM The ROM-in-RAM implementation with 1 MB of boot ROM. For information about the ROM, see Boot ROM. For information about the ROM-in-RAM implementation, see the references listed in ROM-in-RAM Architecture.
Graphics card Three graphics cards are available: NVidia GeForce4 MX, ATI Radeon 9000 Pro, and NVidia GeForce4 Titanium (as an enhancement option). All cards have ADC and DVI connectors. For more information, see Graphics Cards.
Sound On front panel: a built-in speaker and 3.5 mm headphone jack. On rear panel: 3.5 mm line-out jack, 3.5 mm line-in jack, and 2.5 mm Apple Pro Speakers minijack. For more information, see Sound System.
Hard disks An internal Ultra ATA /100 hard disk occupies one of four drive bays in the bottom of the computer and functions as the default boot disk. Space is available in that bay for an auxiliary Ultra ATA /100 device. An internal Ultra ATA /66 device supports two more drives. For more information, see Fixed-Media Drives.
Disk drives Two bays for storage devices with removable-media access through the front panel and four bays for storage devices with fixed media. For more information, see Disk Drives.
Headphone jack The redesigned front panel includes a headphone jack. For more information, see Headphone Jack.
Audio line-in Rear panel audio line-in port for self-powered microphones or other audio equipment. For more information, see Audio Input Jack.
Audio line-out Rear panel audio line-out port for externally-powered speakers or other audio devices. For more information, see Audio Output Jack.
Switches The programmer’s switch and reset button on the rear panel have been removed. For more information, see the below URL for the AppleCare Knowledge Base Article ID: 88330.
SuperDrive (DVD-R/CD-RW drive) Some configurations of the Power Mac G4 computer have a SuperDrive drive. For more information, see SuperDrive.
Combo (DVD-ROM/CD-RW) drive A combination DVD-ROM/CD-RW drive is available as an option. For more information, see Combo (DVD-ROM/CD-RW) Drive.
USB ports The computer has two USB ports, described in USB Ports. The keyboard that comes with the computer has two additional USB ports.
Ethernet The computer has a built-in Ethernet port for 10Base-T, 100Base-T, or 1000Base-T operation. The Ethernet port is auto-sensing and self-configuring to allow use of either a cross-over or straight-through cable. For more information, see Ethernet Port.
AirPort Card An AirPort Card is available as a build-to-order option or as a user-installable upgrade. For more information, see AirPort Card.
FireWire ports The computer has two, 6-pin external FireWire ports that support transfer rates of up to 400 Mbps. For more information, see FireWire Ports.
Modem The computer has a built-in Apple 56 Kbps modem. The modem supports K56flex and V.90 and V.92 modem standards. For more information, see Internal Modem.
Keyboard The computer comes with a full-size USB Apple Pro Keyboard. The keyboard is also a bus-powered USB hub with two USB ports. For more information, see Keyboard.
Mouse The computer comes with a USB Apple Pro Mouse, with optical tracking. For more information, see Mouse.
PCI card expansion slots The Power Mac G4 computer has four, 64 bit, 33 MHz expansion slots for PCI cards. For more information, see PCI Expansion Slots.
AGP-4x card slot The computer is always shipped with an accelerated graphics card installed in this slot. For more information, see Accelerated Graphics Port Bus.
Voltage switching Auto-ranging voltage switching accepts 115 - 250V.
Fan speed control The speeds of the fans are thermally controlled and are automatically set as low as possible, to minimize noise. This is a function provided by the fans and is not controllable by user.
Energy saving Sleep scheduling can be controlled via the Energy Saver pane in System Preferences.
Features of the Enclosure
The Power Mac G4 computer’s enclosure is a mini-tower design with opaque side panels and transparent handles. To access the main logic board to install PCI cards or additional memory, lift the latch and swing the side door down.
The front of the computer’s enclosure has the speaker, media doors for the two removable media drives, the power button with power-on light, and a headphone jack.
The back panel includes the A/C power socket, the I/O ports, and the openings for I/O connectors on the PCI cards.
The enclosure has space for four hard-disk storage and two optical devices. See Fixed-Media Drives.
System Software
The Power Mac G4 computer comes with Mac OS X 10.2 and Mac OS 9.2.2 installed. Mac OS X is the default operating system.
Use the APIs IOKitLib and IOKit.framework to get information from I/O Registry Explorer.
Computer Identification
Rather than reading the box flag or the model string and then making assumptions about the computer’s features, applications that need to find out the features of the computer should use the I/O Registry Explorer calls to test for the features they require.
Asset management software that reports the kind of computer it is run on can obtain the value of the property at Devices:device-tree:compatible in the IODeviceTree plane of the I/O Registry. The model string is the first program-usable string in the array of C strings in the compatible field. For the Power Mac G4, the value of the model property is PowerMac3,6.
Dual Processors and Mac OS 9 Applications
To gain a performance advantage on dual-processor configurations, applications that run in Mac OS 9 must be modified to use Multiprocessing Services, an API that allows applications to create tasks that run independently on one or more processors.
Multiprocessing Services allows you to create preemptive tasks within an application. The application still operates in a cooperative multitasking environment with respect to other applications.
Multiple processor support is transparent in Multiprocessing Services. If multiple processors are available, Multiprocessing Services divides the tasks among the available processors. If only one processor is available, Multiprocessing Services schedules all the tasks with that processor.
Multiprocessing Services allows you to determine the number of processors available before creating any tasks.
To obtain more information, including interfaces and libraries, documentation, demonstration applications, and sample code, refer to the references in Multiprocessing Services.
Power-Saving Modes
The Power Manager is designed to implement a common power management strategy across all Macintosh models.
Processor States
The following processor states are defined:
Run Multiple: The system is running at maximum processing capacity with all processors running at full speed.
Run Single: One processor is running at maximum processing capacity. One processor is running at full speed; all other processors are in sleep mode with their caches flushed and their states saved.
Idle One: The system is idling. All clocks are running and the system can return to running code within a few nanoseconds. All other processorsare asleeping as described for Run Single.
System Modes
The Macintosh system has two power-saving modes.
Partial sleep: The power to the disk drive motors and the display is turned off, but the power supply and fans are still on. The computer can still respond to network activity. Hard drive sleep and monitor sleep can be controlled independently via the energy saver control pane.
Full sleep: The main power supply is shut down. A trickle supply provides auxiliary power to the PCI slots and keeps the DRAM state preserved for a quick recovery. All processors are powered off with their state preserved in DRAM. All clocks in the system are suspended except for the 32.768 KHz timebase crystal on the PMU99 IC. This mode allows the computer to meet the 5 W sleep requirement while providing the ability to start up without rebooting.
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 websites:
http://developer.apple.com/hardwaredrivers/ve/index.html
and
http://developer.apple.com/documentation/Performance/Conceptual/vDSP/vDSP_Library.pdf
Copyright © 2002 Apple Computer, Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2002-09-17