I had extremely good success for 24 hours on prime95 at 4.8 and 5.0ghz (see this link for details on the bios settings i used), at 1.385 and 1.41 volts.. http://www.overclock.net/intel-motherboards/941863-p8p67-deluxe-2600k-5-0ghz-success.html I ran into an issue with the motherboard.. had to have it replaced (if i had more than one ram stick in, it wouldnt post, i also had bsod errors with the same cpu that was working fine).. So i get the new board, put the old cpu back in (had bought another cpu, tried putting it in, but the cpu fault led kept coming on, so i've stuck with the old original sb cpu that hit 5.0ghz).. So i updated to the bios that i had success with.. put the old settings in.. No luck.. I dont even get a bsod, it just spontaneously reboots.. there is no mini dump or bsod.. I've tried a bunch of settings.. including lowering to 4.7ghz.. i've tried setting the duty to extreme and cpu capability to 120%, nothing helps.. I've even increased the volts at 4.7ghz to what i had working at 5.0ghz (1.41) when really it shouldnt need more than 1.385 with this cpu, from its past working state.. I've run out of ideas, short of replacing the cpu yet again (i think the replacement was just a doa) and then redoing the settings custom to the new cpu. Any thoughts? Also wondering if maybe my cpu has decided to go south on me.. (i do have 2 of 4 drives in an my areca addon pciex4 raid which appear to be "missing" but havent had a chance to figure out why). Thanks for any suggestions here.