Running IBT and prime95 at the same time does nothing. They just cancel eachother out. If IBT detects another high draw on your CPU it doesn't ask as much from your CPU. So it's cancelling it out. The best way to stress test quickly is either run IBT or prime95 AND play a demanding game at the same time. That will tell you if your stable for sure. I've tried it and it's crashed many of my "Stable" oveclocks.