GSOD on Power Mac G5 -- advice please

[uberamd]

I have been trying to get a G5 working for a while now with no success. I will just give you a rundown of the situations I am having:

1. The computer passes all Apple Hardware tests from the installation CD that came with the computer
2. The computer turns on and makes the startup chime
3. The computer will show the boot devices (hard drive, DVD, CD, etc)
4. The computer will not boot the OS, just spins and spins under the Apple logo, then turns into the gray "No" symbol. Then the fans start spinning up to full speed, as if the computer is going to take off like a helicopter.
5. The computer will not boot off of the CD/DVD, just spins and spins under the Apple logo then turns into the gray "No" symbol. Then the fans start spinning up to full speed, as if the computer is going to take off like a helicopter.

Its like the computer wants to work, everything SEEMS fine, however it just refuses to boot off of any devices. I have swapped the RAM, video card, hard drive, and DVD drive from a functional G5 with no success. This problem is baffling me like none other because everything LOOKS like it should work, however it just craps out.

Back when it was working it would randomly freeze up and the fans would kick up to full speed. I have gotten it to boot from CD a few times but it was random and not consistent. It kept rejecting the leopard DVD (spitting it out over and over).

Any more suggestions before I throw this thing into oncoming traffic?

 

[wpc33]

1) PMU reset?
2) NVRAM?
3) Did you try a processor re-calibration from the apple service diagnostic(ASD) cd?

 

[uberamd]

1) PMU reset?
2) NVRAM?
3) Did you try a processor re-calibration from the apple service diagnostic(ASD) cd?

Thanks for the suggestions. I did do the PMU reset with the button, NVRAM reset with the open firmware, and the PRAM reset. I haven't done processor recalibration yet, hoping to avoid that.

Here is a slight update, I was able to get Debian 5.0 PPC edition to install on the system just fine, and rebooted a few times and it seemed ok but it did lock up once and the fans ramped up to full speed.

Then, OS X suddenly started booting off the second hard drive, and it ran perfectly and was responsive but started randomly locking up and the fans would kick in to full speed. To me it seemed like the system ONLY locked up when it was idle for a length of time. I watched some youtube videos, setup dual displays, etc and it worked fine but when I let it sit for 30-60 minutes the fans would kick in full speed and it was dead until I force powered it down.

I am puzzled. OS X diagnostic disc claims the logic board is fine, but thats the last thing I can think of that might be dead. And a logic board replacement is not something I care to do.

 

[wpc33]

have you tried booting from a different SATA port?

 

[disconap]

What model G5 is it? If it's not a liquid cooled and you're a tinkerer, I'd actually suggest seeking out a schematic and checking the processor's heat sink (gigantic mass of fanned metal with the G5 logo on the top of it), it's possible that it just needs to be reseated and some liquid silver applied. Though it is odd that the fans kick in when idle, it still could be heat building up and not being dispersed (this would lead to panic mode).

 

[DewGuy1999]

Maybe Power Mac G5 Uniprocessor 5.1.5 f2 Firmware Update