[Zubir]

I have a heavily upgraded G4 Digital Audio that developed a boot problem after I removed the heatsink to apply better thermal paste. In short, I have to press the CUDA button to get the machine to boot after being powered down. If completely powered down and restarted, the power button light comes on immediately instead of coming on after 2 seconds, and the fans will spin up, but I get no video, and the USB doesn't power up (optical mouse doesn't light up.) The machine will soft reboot normally, but will not not boot if the reset button is pressed.

I've:

1. replaced the battery,
2. checked the new battery with a multimeter to verify 3.6v,
3. removed all cards, cables, and power supply connector from the logic board, and let it sit all night,
4. every trick I've come across on the net.

Nothing has worked. So, is it time to buy a new mobo off eBay, or is there some secret method of getting this thing to boot normally again?

[d.fine]

Tried re-placing the CPU? Removing the heatsink could have caused that.

[Zubir]

Yeah, when I removed all the cards, I removed the processor also. Stripped the logic board bare, even the battery, and let it sit all night. I re-installed everything, hit the CUDA button, zapped the PRAM and Open Firmware after that, still have the problem.

[popheader]

I ran into the same problem when updating my sawtooth G4. I added a 1 ghz G4 processor to which before I did this I updated the firmware. After this I too could not boot my mac. I isolated to a bad stick of memory? For what it's worth also you might want to read this too. http://docs.info.apple.com/article.html?artnum=60839

[Zubir]

I think the problem may be that my Sonnet G4 fanless upgrade is dying. The level 3 cache is no longer listed in the "About this Mac..." thing.

[Zubir]

I put my old Apple 533 processor back in, and the boot problem is gone. The Sonnet's level 3 cache is not showing up in the System Profiler, or in Xbench. Is it possible for a processor to continue working with a dead level 3 cache?