I just reapplied thermal paste on my cpu i7-2700k yesterday because the temperature was too high - 40C idle and 75C under load at 4.6ghz. I ran the cpu at 4.8ghz for a month without any problem, but I decided to lower the temperature to make it even more stable. Lowering to 4.6ghz wasn't enough as the max temp was still above 75C, so I decided to lower it further. With 4.5ghz and 1.27 Vcore, the system seemed fine for having a max temperature of 70C after running prime 95 for a while. To my surprise it kept crashing when I played bf3. I automatically assumed that I didn't have enough voltage, so I up the voltage by 0.01 at a time. It crashed again just now with 1.29v.
I suspect that I might have damaged the CPU during reinstallation. I took out the heatsink and the CPU, and wiped down the residue with 70% rubbing alcohol. Cleaning the CPU took some time because there was thermal paste on the side of the top square. I gently took out as much residue as I could with a soft tooth pick and rubbed with non fabric clothing and alcohol very carefully. During the proccess I touched the bottom of the CPU once with my finger on accident, and might have contaminated it with skin grease.
I'm running prime95 again with 4.3ghz while I'm writing this. The temperature has been below 70C. If it crashes again on bf3, I really don't know what to do.
Your cleaning technique is correct! I hold the CPU upside down by the edges, and then use alcohol swabs. Usually 3 swabs will get rid of the old paste.
Please ensure that the heatsink is fastened in a cross pattern tightening manner; as evenly as possible. I make the fasteners finger tight and then tighten 1/4 turn at a time in a cross pattern. Do not over tighten.
Three turns even on fine threads is about 1 mm distance, maybe more depending on the screw pitch, and is too much. It will tend to tilt the heatsink base.
1/4 turn at a time after making the fasteners finger tight would be conservative and very safe. After all you are going to do this maybe once a year?
Point noted, but this still doesnt explain the high temperature and instability. It's been an hour since prime95 started. The temperatures of all cores are generally between 60-65C and peak at 70C. It looks stable so far - no crash or blue screen. I will keep running this for a couple more hours and then run bf3 afterward. What really baffles me though, is it was stable and bf3 never crashed at 4.8ghz, yet it gets so problemetic.