I have hit 3.6ghz on Air cooling with my Q6600. It's quite amazing seeing all 4 cores at this speed...but theres nothing that really utilizes all the power unless im heaviley multitasking, gaming, or modelling in 3ds max.
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Inferno Package/CAI/180tstat/3" DP/AL 104 XP's/3.8 MPS/Tuned