Graphics card: Sapphire 7850 oc (default clocks)
Memory speed: 1448 (181 x 21), therefore underclocked from default of 1600
PCI express is set at 100% I believe, in the Gigabyte bios.
PSU: Antec Earthwatts 650w
I played BF3 for awhile without issues, but yes those stress tests like IBT - Maximum, OCCT - Large data set, Prime 95-small fft were making the monitor turn off and then come back on either a few seconds later or perhaps 30 seconds later. It would happen more than once, for example near the end of each test loop in IBT testing. That kind of tells me the PSU might be strained?
Perhaps not enough amps on the 12v rails, I don't know.