Specifications

Fan Controller

The Power Mac G5 system employs advanced thermal and wattage management to keep acoustic noise to a

minimum. The enclosure is divided into discrete zones, each with independently controlled fans bringing in

cool air from the front of the enclosure, directing it over system components and exhausting it out the rear.

Temperature and power consumption are monitored by the operating system which communicates with the

Fan Control Unit, which in turn controls and monitors fan operation. Note that if Mac OS X is not booted,

thermal management must be provided by the alternate development operating system.

Fan Control Unit (FCU) controls the fans and pumps in the Power Mac G5 and regulates the speeds to run each

fan. The FCU derives fan speed from sensors in each thermal zone. Some of these sensors are thermal while

others monitor power/wattage used in a particular area. It is important to note that there are fixed limits to

fan speed in those areas where power sensors are used. At the upper limits, a fan could be fixed at a particular

speed, based on power consumption, even though that zone continues to generate more heat.

If the FCU does not receive an update from the operating system within two minutes, it begins to ramp up

the speed of the fans to full speed.

Liquid Cooling System

The 2.7 GHz configuration of the Power Mac G5 uses a liquid cooling system controlled by Mac OS X to manage

the temperature of the processors in the computer. The liquid cooling system works in conjunction with the

air cooling system and is designed to to optimally cool internal components as quietly as possible. The liquid

cooling system is sealed and is not designed to be opened.

Warning: Do not attempt to open or service the liquid cooling system. Opening the liquid cooling

system may damage your equipment, and such damage may not be covered by the limited warranty

on your computer.

Architecture

Fan Controller