Quoting primesuspect

Xtremesystems had a party at CES that we sadly had to miss (well, Fatcat and Pseudonym made it), but anyways - they hit 6.4ghz last I heard. Liquid helium.

Ok lets get some facts out about the PhenomII at the Xtremesystems party.

It was on liquid helium. They got WCPUID of 6.5ghz. The were able to do 3DMark05 @ 6.3ghz with 2 cores lower clocked to 6.0ghz and running @ -240c (thats not a typo)

The best we saw the "Sekrit i7 975" that intel was using was 5.3ghz on LN2.