Looks like someone has broken the 6ghz barrier. They overclocked a P4 Prescott from 3.6ghz to just over 6ghz at 1.3ghz FSB. They cooled it using liquid nitrogen.
I'm guessing it's not too stable. I wonder how long it can hold that. Probably end up snaping under the huge amount of stress. Anyway check it out yourselves
http://www.xtremesystems.org/forums/sho ... ge=1&pp=25