If you look a few posts up you will see my q6600 1hr blend prime stable at 514fsb, which did turn out to stay stable. So to answer your question yes it can run 500+. I would try with higher mch. It takes mine about 1.6v for 500 to be fully stable with my q6600. I dont know if quads tend to need more for 500 then a dual core or not. Even with 1.75v on my mch it stays a cool 43c at full load but for some reason I think its bugged, that is what the probe says though. Try a higher mch