Specifications

Power Mac G5 (Late 2005) Troubleshooting — General Information 138

Important: Combined maximum power consumption for all four expansion slots should not

exceed 200 W. Combined maximum video RAM for all graphics cards is 1 GB.

While all slots can accommodate PCI Express cards that have up to 16-lanes, if you install a card

that requires a greater bandwidth than the slot provides, the card will operate at the bandwidth

of the slot. For example, an 8x card installed in a 4x slot will operate as a 4x card. Refer to the

following table for details.

PCI Express Slot Bus Bandwith (x) Connector (Lane)

4 4x 16 lane

3 8x 16 lane

2 4x 16 lane

1 16x 16 lane

Thermal Calibration

To ensure proper fan and temperature control in the Power Mac G5 (Late 2005), you must run

Apple Service Diagnostic whenever you replace a processor or logic board with a new processor

or logic board. Apple Service Diagnostic for Power Mac G5 is available as a download from http://

www.info.apple.com/discimages/.

Note: The calibration process of Apple Service Diagnostic requires a controlled environment to

ensure accurate ambient temperature readings. Computers under test must have the transparent

air deector installed and the door sensor switch must be operable. Units under test should also

be located away from heating and air conditioning systems and fan exhaust of other machines.

Ambient temperature should not go above 77 degrees Fahrenheit or 25 degrees Centigrade.

Resetting the Logic Board

Some system problems can be resolved by resetting the System Management Unit (SMU)

microcontroller chip on the Power Mac G5 (Late 2005) logic board. To reset the logic board, do

the following:

Shut down the computer.

Unplug the computer from its power source.

Wait two minutes.

Plug the power cord back in, and turn the computer on. If the computer does not power on,

there is something else wrong with it; refer to the “Startup Failures” section of “Symptom

Charts” in this chapter.

You can also reset the logic board by pressing the SMU reset button on the logic board:

Shut down the computer.

Open the computer, lay it on its side with the access side facing up, and remove the front

inlet fan assembly.