I've managed 4.2ghz so far, but i keep getting random freezes and bsods, i think its a memory issue though. Running 1.475v in bios, somehow it ends up at 1.55v in windows though. Should be able to push farther as temps are still under control, ive just been too lazy to care as this thing is so much faster than my q6600 ever was. Running at 3.2ghz (dummy overclock in bios) daily as its rock solid stable and still plenty fast.