How Can I tell if GPU or PSU is faulty?

Hi,

Recently my PC stopped booting up. Happened before and a CMOS reset fixed.

This time it hasn't, nor has a deep CMOS reset or reseating and cleaning everything.

I beleive the fault is not hard disks as I have Windows 7 on a RAID set up and Ubuntu on seperate standard disk. Neither work.

I have suspected that it was either the Motherboard (IP35 Pro), the PSU (700w) or the GPU (8800 gts). The motherboard lights are on and the codes are often FF or 7F.

I tried another, smaller GPU in the PCIe slot and the system then boots - BUT I don't know if that means my graphics card is faulty or the PSU, because my GPU needs a lead from the PSU directly, where as the one I tried that worked doesn't.

Any idea how I can tell if it is the GPU or PSU? I can't afford to shell out on a new card if it doesn't work.

Thanks

Pretty sure (95%+) it's the GPU. AFAIK the 8800GTS just pre-dates nVidia's $1 billion solder mistake. However, that just means it's not guaranteed to fail like G92, G84, G86 etc., nVidia were so evasive about the whole defect thing that it's impossible to be sure. Either way a lot of 8800GTS's and GTX's seem to die anyway - possible because they are hot, power hungry cards anyhow.

So you've tested another card and it worked, so that rules out mobo, CPU or RAM and the PSU provides at least enough juice for the other card. Behardware.com measured the 8800GTS at around 50W idle at the Windows desktop (LINK), which is not that great but you can pull more than that by stressing your CPU. Since almost everything these days draws mostly 12V from the PSU, to test your PSU you can just load your CPU 100% and if it works your PSU should be well able to handle your 8800GTS. In other words: the GPU is kaput :(

One of those which is hard to say without more testing, ideally you need to test the pc with a different psu and test the gpu in a different pc to rule out one or other