Some good trouble shooting tips to help fix start up issues and fix
Very important note: If your computer does not retain parameter RAM or PRAM settings when it is turned off, then generally this indicates that the battery needs to be changed. Make sure that you know that you have to reset the PRAM before you continue. Before doing this step you must first know that you are trying to fix major issues with with your Mac Pro.
Resetting PRAM and NVRAM
1. Shut down the computer.
(You will use the following keys on the keyboard only when you are ready to turn on the computer)
2.Turn on the computer and quickly hold down the following keys.
Command-P and Option-R.
(You will need to hold these 4 keys down simultaneously)
3.You must hold the-Option-R-Command-P keys in combination before the gray screen appears
4. Hold down these keys until the computer restarts and you hear the startup sound for the second time.
5. After hearing the startup tune for the second time you can release the keys.
Your computer's PRAM and the NVRAM are reset to the default settings. The clock settings may be reset to a default date on some models. Make sure to set your date/time to the current date and time.
This will help in some troubleshooting situations, if resetting PRAM does not resolve an issue, resetting the PMU may be the next appropriate step.
To reset the SMU on a Power Mac G5 (Late 2005) computer
1. Turn off the computer by selecting shut down from the Apple menu or by holding the power button until the computer turns off.
2. Open the metallic outer door and the inner plastic air deflector, remove them both.
3. Remove the fan assembly to the left of the processor module.
4. Press the SMU reset button on the logic board, it is next to the memory slots (small square with a white or gray button)
5. Replace the fan assembly first then the air deflector, and then the outer door.
6. Turn on the computer.
