strange crashes with iMac8,1 24"

[finbarqs]

I have an iMac that has been crashing without any type of warning. The mouse cursor would move, but the clock would stop. I would literally have to hard reset the computer to get going. This would happen almost immediately, or within 5 minutes. One time, I saw a completely blank white screen.

I've tried repairing the permissions without the installation discs, but it didn't work. Has anyone run into these issues?

AHT reports no issues, even the advance test.

 

[Emulex]

sounds like its applecare time! if you've done a factory osx restore and it does this something is jacked up.

maybe tail dmesg log or one of the /var/log files remotely so when it happens you can see whats going on.

 

[finbarqs]

update: it does it in boot camp also!

 

[finbarqs]

funny, safe boot, nothing happens! Everything is fine in safe boot! running prime 95...

 

[Hellhammer]

Try SMC and PRAM resets. Reinstalling OS X might help too if those resets don't (it won't erase any data).

 

[finbarqs]

PRAM, SMC resets tried, Reinstalling OSX just results in a black screen.... Actually further diagnostics resulted in taking the imac apart.

Changed the HDD (might as well) and SL installs without a hitch! connected the old drive, and everything is working without any issues! The only thing different now, is that it's laying flat on it's back, and it's open. (panel is also disconnected). Everything seems to be fine.

this is a 2008 intel iMac

3.06GHz
2GB of RAM
8800GS MXM 512MB ram.

I occasionally would get panic logs too... but didn't really help me that much after searching for entries in regards to the log.

I suspect the system's GPU maybe overheating... I don't think it's damaged yet, as I'm not getting any graphic anomalies..

I guess the support for this thesis would be that safe boot would work without a hitch, running p95 for OSX for 16 hours (CPU reached a temp of 98C max -- 2C away from max threshold!) since Safe boot would load the mininum (not even the GPU driver...)

 

[Hellhammer]

NVIDIA 8800GS is known to fail. There are many threads about this in MacRumors so you are not alone with this issue.

 

[finbarqs]

scratch that... in bootcamp, running 4 instances of prime 95 will be okay (2x CPU, 2x MEM)

Then as soon as I run 3DMark 2005 in a loop, crashes the whole system! I think we have our culprit!