Apparently random restarting (No BSOD). Stability passed.
I have a rather confusing and frustrating problem here. I'll start with computer specs then explain what I'm experiencing:
Intel Core i5 750
Xigmatech Dark Knight NightHawk Edition (heatsink)
Asus P7P55D LE
RipJaws Gaming Ram F3-12800CL7 (2 x 2GB)
Sapphire Radeon HD 6870
7500rpm Samsung 500GB sata HDD
Usb Front Card Bay
Sony sata CD/DVD writer
It all began after I noticed temps of 95+ on my i5 under max load with stock cooler. I believe CPU was getting throttled which was noticeable. I reapplied thermal paste dropping temps right down, and decided to buy an after-market cooler (the Xigmatech listed above) so I could also overclock.
Once everything was fitted, I began monitoring temps using RealTemp and InteBurnTest (maximum) and they were around 20 idle and 45ish under load. So I decided to go ahead and overclock.
EDIT: CPU temps don't pass 60-65 degrees celcius for any of the following:
I was only aiming for 3.6 - 3.8GHz on overclock. I achieved stable bclock (180 and 190MHz at 1.3VTT).
SPD set to 8, Ram timings set to recommended 7-8-7-24, and DRAM voltage set to 1.6 (Mobo only allows 0.1 change, so 1.6 or 1.7 really which I think is odd). Memtest ok and again system was stable.
I went for the full overclock:
Bclock = 190MHz
CPU clock ratio = 20
VTT = 1.3V
SPD = 8
Dram = 1.6V
Vcore = 1.3V
PLL = auto
PCH = auto
LLC = enabled
Power saving features disabled
I ran IntelBurnTest (maximum)(3 loops), the computer passes it, then immediately restarts with no BSOD. I try again a few more times, and the computer does the exact same thing. Gives me Passed Stability test notification to proceed to immediately restart with no blue screen.
I update Bios to latest here.
A bit confused and after a few more tries with slight tweaks (Bios tweaks and checking all components are seated/connected properly) and the same thing, I lower the bclock to 180MHz, set Vcore to auto (happens to be 1.256V on testing). Set the PLL = 1.9 and PCH = 1.15, and try again.
I complete an hour of IntelBurnTest and pass the stability test, and the computer is fine. So I run a few hours on OCCT with a large data set, and it is also perfectly stable. I left the computer running the full night as well with no problems.
When I woke up today, and attempted to restart it, the computer kept rebooting non stop at various points during boot, sometimes getting to windows loading, and sometimes getting fully into windows before restarting (only one bsod). Many of the times though it doesn't get up to the boot screen.
I was getting Your overclock has failed, Press F1 to lower the clock or adjust the BIOS or F2 to load defaults, and it doesn't matter what I do.
I already know the computer is stable with the overclock, but it does it even if I default back to stock. Just random restarting. I thought maybe the power supply is getting old or faulty, but I can't find any proof of this or a pattern. By removing unnecessary components, defaulting the BIOS (which should run perfectly well at stock, because it has been doing for ages), I still can't come to a logical conclusion of the fault.
I originally thought maybe the hard drive was causing it, because minimum write speed was extremely low during tests, but removing that from the equation makes no difference.
If I overclock it's more likely to restart, I think. But that instability seems to carry over even when I default the BIOS. However if I leave the computer and come back a bit later, things seem to be OK (I'll monitor this).
This is all on a fresh install of windows, but I'm pretty sure that does not matter.
I'll leave the bios at default settings, and monitor the situation (I'll probably do some stress testing to see if I can force a problem since the computer is running ok with default settings right now), but any suggestions and advice will be greatly appreciated. If I can narrow it down to a faulty component, I'll go ahead and replace, but I can't find proof of that so far.
Thank you greatly in advance, and sorry for the wall of text. If there is anything important you think I haven't mentioned please ask.
EDIT: Computer restarted when running IntelBurnTest (maximum). It proceeded to restart 4 times without even reaching boot screen, then on the fifth time it was able to fully boot into windows. Seems to only happen when CPU is under load, as far as I've witnessed. All this only occurred after I tried to overclock.
EDIT: Whatever is happening is getting worse. I can barely keep the computer on now. Everything Powers up for about 2-3 seconds then switches off and restarts. Can occasionally boot into windows, where it is likely to restart soon after.
EDIT: After deciding the probability of it being the PSU was high enough to warrant a replacement, I bought and fitted a new one. Everything seems fine now.