Troubleshooting the Power Mac G5: Thermal management considerations; Older AGP Cards will not work; more
Troubleshooting the Power Mac G5: Thermal management considerations; Older AGP Cards will not work; more
The following is a preliminary assessment of some potential troubleshooting issues that may arise with the Power Macintosh G5, based on developer documentation released by Apple and a few first-hand reports.
Thermal management considerations One major consideration for those planning to run Linux or another operating system flavor on the new Power Mac G5s is that thermal management must be provided by the alternate operating system.
In other words, if you are not booting into Mac OS X, the G5 may not perform to normal spec and may actually shut itself off or engage processor cycling (lowering the chip(s)' clock speed) in order to reduce generated heat.
Also, unlike some previous Power Macintosh models that can be run with the case open and suffer no ill effects, the G5 can not be run with the side panel open. The reason is that there is an air deflector inside the enclosure that is not intact when the case is open, potentially causing overheating.
Power limitation for PCI cards Apple says that in order to satisfy cooling power supply requirements, a total of 90 watts is allocated to the three PCI or PCI-X slots and the AGP Pro slot.
No change from previous models here, except that in the last generation of Power Macintosh G4s, the maximum total power available for all four PCI slots and the AGP-4x slot is 90 watts.
Like previous models, the connectors include a PME signal which allows a PCI card to wake the computer from sleep.
More juice for the AGP slot One major difference from previous G4 models is that the AGP 3.0 8x Pro slot can account for up to 75 watts of that total, depending on which card is installed. The AGP-4x slot found on G4s can account for up to 30 watts of that total, depending on which card is installed.
This is to compensate for the latest round of graphics cards that consume ever-increasing amounts of power and sometimes can take the room (and power) of more than one expansion card.
Older AGP Cards will not work Of important note is that the AGP bus is 1.5 V only and is not backward compatible. Older AGP cards will not work in the Power Mac G5 computer.
Feedback? Late-breakers@macfixit.com.Resources