The thing about Prime 95 is I've found that it'll catch even slight instability. I know a few people say their CPU will run Prime 95 just fine, but lock up when they encode video or something. But I've never had problems with instability if a CPU will run Prime 95 forever... I have found out though that there are certain intervals where my CPU's have become unstable. For example... if the RAM is very unstable, it errors out right away, if it's a little more stable, it takes 4 minutes to error out, if it's still not quite stable it takes 7 minutes. If it runs longer than 7 minutes, I've never had problems with RAM stability. As far as CPU stability, errors either show up within the first 2 minutes, just before 1 hour, just after 2 hours, right around 4 hours, just after 7 hours, or never.