The conversation on this page has been archived and is no longer active.

What happens if you reset the PMU too many times.......

Message #1 - Posted 2004/03/16 - Paul Walker

And what can you do to prevent the PRAM from going dead the next time?


Paul Walker

Previously, London Ham Radio Club wrote:

I have a G4-350 tower with PCI (not AGP video). I picked this machine up used a few days ago. I installed a new 80gig HD and loaded 10.3. The installation went ok and the machine appears to be stable. BUT... I must perform a reset (Opt-Alt-P-R) everytime I boot up. After a few chimes, the machine starts ok. If I shutdown and then push the power button, the machine chimes and appears to start for a few seconds, I never get the rastor and the machine just sits there. The OS does not appear to start. If I then hit the reset button then pram reset, I am good to go until I shutdown.

The machine only has Apple ram although I tried others; no change I tried another video card; no change
I removed the SCSI card; no change
I tried another battery; no change

There doesn't appear to be a firmware upgrade for this machine although the Apple site was confusing. This link suggests that no upgrades were available:

Anyone experience this before? Is the machine sick or it OSX corrupting the pram?

As you are doing a PRAM reset each time you start, it may be related to CUDA OR PMU problems or even the PRAM battery.

At least try:
replacing the PRAM battery (usually a 3.6 volt available at Radio Shack @ $10 or so, cheaper computer sources).

Near the battery on the motherboard is a small button. On older machines this was called the CUDA reset and newer Macs the PMU. Some may mention this as Hardware reset. This controls power startup issues on the motherboard and parameter ram issues.

With G4 off, Press this button ONCE for about 2-5 seconds. Then try restarting your G4.

(Pressing this button MORE than once can cause the PRAM battery to go dead within days instead of 3-5 years)

Good luck & I hope it works for you.


Message #2 - Posted 2004/03/17 - leeg

Paul Walker wrote:

to answer the subject, if you reset the PMU too many times, you can crash it. Then the PRAM battery life shrinks from 5 years to 2 days, and the computer will only turn on if you're lucky.

Graham Lee
I am leeg, for we are many
"The internet is a gateway onto the net." - Bob Dole.

Need Help? Have a Question?

Looking for more help, comments, and answers?

Ask your questions on Ask Different. Ask Different is a community of Apple users ready to help.