New
#11
Well, there's always CPU cache. And some mobo's have a bit of memory built in (at least they used to - back in the olden days).
Try running the Small FFT's and the Large FFT's test in Prime95
Also try running the video tests anyway - it will also test the channels to the memory (inferred)
The more tests we run, the more likely we are to be able to find the issue.
IME it's more common to lose a mobo than it is to lose a CPU - but every case is different.
When you BSOD'd with the other graphics cards, was the onboard video disabled in the BIOS?
If not, I'd try it again with it disabled. If not disabled then the onboard stuff will still be running - with maybe a software switch causing the switch to the add on card (which would leave the onboard card running, but not active).