ADC Home > Reference Library > Reference > Hardware & Drivers > Apple Hardware > Power Mac G5 Developer Note >

< Previous PageNext Page > Hide TOC

Overview to the Power Mac G5

The 64-bit desktop Power Mac G5 uses dual PowerPC G5 microprocessors and is intended for use in content creation, desktop publishing, multimedia, scientific and technical applications, and other activities that require high performance.

In this section:

New Hardware Features
Hardware Features Summary
Features of the Enclosure
System Software


New Hardware Features

Here is a list of the new hardware features of the Power Mac G5. A list of all hardware features is provided in “Hardware Features Summary.” A comparison of key feature differences are listed in Table 1-1.

Hardware Features Summary

Below is a list of all of the hardware features of the Power Mac G5. The major features are described more fully later in this note. To view the Technology and Performance Overview document, refer to http://www.apple.com/powermac/.

Table 1-1 lists the key differences between the features of the dual 1.8 GHz configuration and the dual 2.0 and 2.5 GHz configurations.

Table 1-1  Feature comparison of configurations

Feature

dual 1.8 GHz configuration

dual 2.0 and 2.5 GHz configuration

G5 Processor clock speed

1.8 GHz

2.0 or 2.5 GHz

System bus speed

half speed of processor

half speed of processor

System controller

U3

U3H

Device/disk controller

K2

K2

SDRAM

4 slot DDR400 SDRAM with max 4 GB

8 slot DDR400 SDRAM with max 8 GB

PCI

3 64-bit 33 MHz PCI slots

3 PCI-X slots

Power supply

600 W

600 W

Features of the Enclosure

The Power Mac G5 computer’s enclosure is a tower design. Figure 1-1 illustrates the front of the enclosure and Figure 1-2 illustrates the rear of the enclosure.


Figure 1-1  Power Mac G5 front view

Power Mac G5 front view


Figure 1-2  Power Mac G5 rear view

Power Mac G5 rear view

The enclosure has space for two hard disk drives and one optical device. See “Hard Disk Drives.”

To access the main logic board to install PCI or PCI-X cards or additional memory, refer to “Expansion.” For full details regarding opening and accessing the computer, refer to the Power Mac G5 User’s Guide that was shipped with your computer.

!

Warning: Opening the enclosure side panel impacts the thermal performance of the computer. Do not run the enclosure with the side panel open. If the air deflector inside the enclosure is removed, the fans will spin very slowly and the system will take action to prevent over-heating.

System Software

The Power Mac G5 ships with Mac OS X 10.3.4 or later installed as the default operating system. The classic environment can be used to run Mac OS 9 applications. Load the Classic application from the “Extras” CD shipped with your computer.

To retrieve information from the I/O Registry, use the APIs in the header file IOKit/IOKitLib.h.

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 I/O Registry 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 G5, the value of the model property is PowerMac7,3 .

Power Management

The basics of Power Mac G5’s power management techniques are described in the following paragraphs.

Processor and Bus Slewing

To lower power consumption, heat generation, and fan noise, the Power Mac G5 computer incorporates an automatic power management technique called bus slewing. Bus slewing is designed to run at high processor/bus speeds and high voltage when the demand on the processor is high, and to run at low processor/bus speeds and low voltage when the demand on the processor is low.

Note: The memory bus runs at 400 MHz and does not slew.

Switching between different processor/bus speeds and voltages is achieved by a gradual transition that is designed to minimally impact system or application performance and typically operates seamlessly to the user. In slewing, the bus runs at half the speed of the processor.

The ranges of the slewed processor speeds are listed below:

Configuration

Processor range

1.8 GHz

1.3 GHz to 1.8 GHz

2.0 GHz

1.3 GHz to 2.0 GHz

2.5 GHz

2.0 GHz to 2.5 GHz

In addition, the Power Mac G5 computer allows the user to control bus slewing mode. The options for specifying either high, reduced, or automatic processor and bus speeds are located at System Preferences>Energy Saver>Options; then select Automatic, Highest, or Reduced.

Note: For best performance when using professional applications with high demand on the system (such as Final Cut Pro or Logic), you may want to set the processor/bus speed option to highest.

If the Power Mac G5 computer detects a processor temperature that is high, due to high ambient temperatures or other factors, it will automatically enter bus slewing mode regardless of the selected setting.

Processor States

The following processor states are defined:

System Modes

The Macintosh system has the following power-saving modes. If the system does not support full sleep, it will use the less efficient doze mode.

Velocity Engine Acceleration

The Velocity Engine is the vector processing unit in the PowerPC G5 microprocessor. System software has been modified to take advantage of the accelerated processing that the Velocity Engine makes possible and 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



< Previous PageNext Page > Hide TOC

© 2003, 2004 Apple Computer, Inc. All Rights Reserved. (Last updated: 2004-06-29)

Did this document help you?
Yes: Tell us what works for you.
It’s good, but: Report typos, inaccuracies, and so forth.
It wasn’t helpful: Tell us what would have helped.