HW BSOD

Hi!

I've experiencing BSODs on my win7 but I think they're caused by HW errors. I've a fairly new HW configuration. BSODs error codes are quite random, I've already discussed this in the SW part of the forum. I've already changed my memory modules cause they seemed to be faulty but BSODs still exists though they're not as frequent as before. Mostly BSODs happens when a lot of memory is used. For example FF is opened with lot of tabs and torrent is running too or during games. I've run OCCT & Prime95 both ended with errors. The two progs showed the same trend: with high processor and low memory (or bus) activity (Prime: smallFFt, OCCT: small data set) it run a bit longer but with blend, large FFT it stops with error nearly immediately.
Please give me some hint on how can I determine if it's a processor or motherboard error?

Thank you,
Akos

System specs:
Motherboard: Gigayte MA790GPT-UD3H
Processor: AMD Phenom II X4 955
Memory: OCZ Gold Low Voltage 2 x 2 GB DDR3-1333 PC3-10666

Run Memtest86+ on each stick of memory individually, preferably overnight.

Memtest86+ - Advanced Memory Diagnostic Tool

What was indicated by the Blue screen as the cause?

I've BSODs caused by these drivers (+BSOD code): ntoskrnl.exe (0x3B), atikmdag.sys (0x116), dxgkrnl.sys (0x116), mpfilter.sys (0x1E).
I did some search on atikmdag.sys and I've found that it can be caused by overheating. That can be a real issue on my side because I use the integrated GPU. My CPU temps is also very high ~70°C during CPU tests (amd official max temps is 62°C). Although OCCT large/medium data set tests fail before it could reach 62°C but small ds test goes up to >70°C without a failure (prime95 show similar results).
I'll run memtest86+ as u said although I suspect rather a motherboard or CPU error (or temp?).
Minidumps attached.

thx