Bios all the way. When i got the spec in sig i tried the asus turbo v utility in windows. For a light oc of 4.2ghz, it was setting the vcore to 1.2700 ono. Temps were getting a bit high for such a mild clock. By using the bios, i was able to run at 4.5ghz on 1.300 vcore set in bios, (1.272 @ load). Temps pretty much the same, but the voltage set on the windows oc was likely too high.