You're darn lucky you didn't have an old socket A Duron in there! BOOM!
Anybody have a link to the old THG video where they pulled the heatsinks off of P3, P4, and the original Athlon under load? The intels all throttled to save themselves, but the AMDs, well, BOOM! about sums it up. I assume AMD has fixed that by now and I know Intel still has the throttling.