The guys over at HardOCP have managed to fry a 1Gz athlon, a 2Gz P4, A 3Gz P4 (while cooled to -25C and also running at 4.2Gz!) and now they are cooling a 3gz P4 to run at 4.44Gz in this article. Quite interesting. Twin Vapochills and water cooling all in one case. sounds like fun!