In my experience, the vast majority of the Q6X00 lineup could do 3ghz no issues, most could do 3.2ghz some could do 3.4ghz and a few could do more. But 4ghz?? Good grief yes that's a golden sample!
The worst for mine, was so many "Bus/Interconnect Error" WHEAs at only 367 MHz FSB, FFS! Yes, mine did 3.3 GHz, in fact at only 1.4V/1.39V? (That wasn't a lot of Vcore for 65nm!) Looked like the bus errors stopped me before I could even try 3.4!
Linpack passed at 3.3 GHz core speed, but Prime95 blend failed with "Bus/Interconnect Error" WHEA error, until I turned up the FSB termination voltage to 1.35V and even then, I have to keep it cooler than usual, for especially a low load, otherwise, the same error is back, even when running nothing demanding!
Linpack didn't reveal bus instability like Prime95 blend did.
