Every 2-3 months, my 1.8 GHz Dual Processor G5 (purchased 2004) will begin to make a "revving up" nose. It continues to get louder and louder. The screen freezes and my arrow will not move. I can not turn off the computer from the monitor or the on/off button on the front. I have to unplug it to stop it. I do not know what would happen if I did not unplug it. I first noticed this after my 3 year warranty plan expired. Does anyone know if this is a serious issue?
Some system problems can be resolved by resetting the PMU. These include:
No power / computer does not function
USB and/or FIreWire port(s) do not function
Computer does not sleep / wake from sleep
To reset the PMU on the Power Mac G5 follow these steps:
Disconnect the power cord and check the battery in the battery holder. The battery should read 3.3 to 3.7 volts. If the battery is bad, replace it, wait ten seconds, and then proceed to step 2. If the battery is good, go directly to step 2
Press the PMU reset button once and then proceed to the next step. Do not press the PMU reset button a second time because it could crash the PMU chip.
Wait ten seconds before connecting the power cord and powering on the computer.
NOTE: The steps above reset the computer's PRAM (parameter RAM). After resetting the PMU, be sure to set the time, date, and other system parameter settings.
SMU Overview
The SMU (System Management Unit) is a microcontroller chip on the logic board that controls all power functions for two models of Power Mac G5 computer.
Power Mac G5 (Late 2004)
Power Mac G5 (Late 2005)
If one of these Power Mac G5 models is experiencing any issues regarding these functions, resetting the SMU may resolve the issue.
The functions controlled by the SMU include:
It tells the computer when to turn on, turn off, sleep, wake, idle, and so on.
It handles system resets from various commands.
It controls the fans.
NOTE: Resetting the SMU does not reset the PRAM.
What SMU Reset Does and Does Not Do
Resetting the SMU will not resolve issues in which your computer is unresponsive--in these situations, restarting your computer will generally suffice. If your computer isn't responding, perform these steps one at a time, in this order, until the issue has been resolved:
Force Quit (Option-Command-Escape)
Restart (Control-Command-Power)
Force Shut Down (press the power button for 10 seconds)
Resetting the SMU can resolve some computer issues such as:
not starting up
not displaying video
sleep issues
fan noise issues
If an SMU-equipped Power Mac G5 computer still exhibits these types of issues even after you've restarted the computer, try resetting the SMU.
SMU Reset for Power Mac G5 (Late 2004)
Turn off the computer by selecting Shut Down from the Apple menu or by holding the power button until the computer turns off.
Remove the power cord from the computer.
Wait two minutes.
Plug in the power cord.
Turn on the computer.
SMU Reset for Power Mac G5 (Late 2005)
To reset the SMU on a Power Mac G5 (Late 2005) computer, either use the steps listed above for the Power Mac G5 (Late 2004) or:
Turn off the computer by selecting Shut Down from the Apple menu or by holding the power button until the computer turns off.
Open and remove both the metallic outer door and the inner plastic air deflector.
Remove the fan assembly immediately to the left of the processor module.
Press the SMU reset button on the logic board.
Replace the fan assembly, air deflector, and outer door.
Turn on the computer.
Thank you for all the information. Do I try to reset the PMU and the SMU, or just try the PMU and see if the problem occurs again before I try to reset the SMU?
