My chip does 850 fine and i had it on 900 for several days. The other day I had it going full blown for several hours and when i rebooted it locked in windows while at 900mhz. I have backed it down to 850mhz. This has to be a heat problem. I only have one fan in the bottom of the front of the case. I have now added one in the front at the top. I really do not think this helps the cpu which is at the back. Should I make a hole in the case and put one in the top near the sucking air out or in? I think I need better case cooling. My two motherboard monitor temps for the case are currently on 22c and 27c. Thanks!