I played games for like 4 hours straight, no restart, pretty sure it's the PSU now, can't believe I've actually managed to max out a PSU.
I'm actually running a 5960x at 4.4Ghz, I think that's easily 200w, although there's no way to tell, no software I've tried is giving me sensible numbers.
If I then put my GPU on 400w, I could easily be blowing my power budget. The reason I didn't think this was the problem was because as soon as the system restarts, I thought it was the PSU, I usually immediately dial back the CPU so save power, yet it still restarted, probably because the PSU was still running hot and haven't cooled down to within specs yet. So that threw me off into thinking it was the GPU.
It's no big deal though, since I wouldn't be running this GPU at 400w everyday anyway, efficiency goes to **** after 200w, there's barely any improvement in real games going from 200w to 400w, and I know this can run 300w indefinitely.
On the CPU side, I just put in a current limit, now it's still running up to 4.4, but if running all 8 cores it will get down to 4.0, I with this has proper turbo boost power controls, instead it's totally busted and telling me I'm only at 70w when my 140amp current limit is in effect.