Under-Volt/Clock seriously overheating Nvidia 8800 GS GPU

[KNASEN]

Dear all,

 

I have just bought an imac 8,1 24" 3.06GHz that behaves terribly. Whenever do the least graphics intensive task (i.e opening a folder) the everything freezes with artefacts on the screen. I have tried to put the fans on max with SMC Fan Control with only some minor improvement, and the same goes for having freezing room temperature. Graphiccelerator does not support the Imac, and Rivatuner only works in windows.

 

The computer is out of warranty and I am truly desperate and in dire need of help!

 

Is there any nice soul who could guide me to how I could remedy this by any means - DSDT or KTEXTS?

 

If I could either:

— Turn down the clock speeds

— Get the GPU to throttle heavily

— Turn down the voltage to the card

I would be ever so grateful! Thank you!

 

Edit: Since it's an Nvidia card that needs hacking I am hoping this is the correct forum for the question

[kch0pa]

First of all you should try a complete reinstall of OS X. Then, if that doesn't work, try checking the temps on the graphic card and then cleaning the ventilation system of the computer; that involves opening it up, but since it's out of warranty, that shouldn't be a problem. If that doesn't work, you have a defective graphic chip, undervolting may solve the issue, but its not a permanent solution.

[KNASEN]

First of all you should try a complete reinstall of OS X. Then, if that doesn't work, try checking the temps on the graphic card and then cleaning the ventilation system of the computer; that involves opening it up, but since it's out of warranty, that shouldn't be a problem. If that doesn't work, you have a defective graphic chip, undervolting may solve the issue, but its not a permanent solution.

 

Thanks for the reply kc0pa! Appreciated

 

I have done a complete reinstall, which sadly didn't remedy the situation. The temps of the graphic card range from 65-105 degrees celsius (149-221 farenheit). The ventilation is also quite clean.

 

So I have a defective chip. The 8800GS in the 8,1 Imac is apparently plagued with this manufacturing defect.

 

After seeing a specific kext in the Kernel Panic reports I tried removing of the NVDAResman.kext which helped a lot and remedies the lock ups. But is severely laggy when it comes to playing back video from youtube, quicktime etc.

 

I would really love to undervolt the graphics to stop the locking up but keep some video functioning. How do I do this?

[kch0pa]

Here's a thread I found on the subject. Seems like the solution would be replacing the whole logic board.

http://forums.macrumors.com/archive/index.php/t-1085213.html

Not sure how you'd underovolt your GPU; CPU's can be done with CoolBook, GPU's would probably involve ROM hacking, and I'm not sure how you can do that. Of course it would be a lot easier on Windows, you could use RivaTuner. Try dumping the ROM with some tool on Windows or Linux and then asking someone for help on how to patch it.

[AREOS]

Thanks for the reply kc0pa! Appreciated

 

I have done a complete reinstall, which sadly didn't remedy the situation. The temps of the graphic card range from 65-105 degrees celsius (149-221 farenheit). The ventilation is also quite clean.

 

So I have a defective chip. The 8800GS in the 8,1 Imac is apparently plagued with this manufacturing defect.

 

After seeing a specific kext in the Kernel Panic reports I tried removing of the NVDAResman.kext which helped a lot and remedies the lock ups. But is severely laggy when it comes to playing back video from youtube, quicktime etc.

 

I would really love to undervolt the graphics to stop the locking up but keep some video functioning. How do I do this?

 

Can you please provide a IOREG registry save?, to seek if there is any thing wrong, I have this card in my laptop Gateway P6801 and I dont have any heat issues I need to compare them .