Using asus p8z77-v lx, i5 2500k 4.2Ghz 1.3V, i only changed voltage and multiplier. I ran prime95 blend for about 10 hours, i also tried combination of prime95 and furmark and OCCT PSU stress test. It is all stable. Today i played starcraft 2 and after a few minutes it crashed (first white screen then restart). I even tried upping voltage to 1.325V and it didnt help - took a while longer but still crashed. Then i put frequency to 4.1Ghz at 1.325V and it didn't crash anymore. This doesn't really make sense since prime95 + furmark stressed my cpu a lot more then the game. Temps during stress are cpu 70C, gpu 80C, starcraft 2 my cpu is 60C, gpu is 70C. I am thinking there must be something else beside cpu voltage. Because even 1.3V for 4.2Ghz is not good at all. I had another i5 2500k chip and it was the same.