With my 6600k ive got it to 4.7ghz on 1.35v (not my everyday oc. 1.28v and 4.5ghz is everyday) but what i found is that with 1.35v it boots at 4.9 and runs aida 64 for a while. but once you switch to something that isnt a stable load like cinebench or such, it will BSOD. Not going to push more...