Well I was able to get to 3.6 with my Q6600 go but temps are a concern. Although I can stay below the “stock”max temp of 71 lower would be better. I am on air and Cores 1 &2 consitantly run about 5-6 degrees hotter than 3 and 4. Could the weight of my extreme 120 be tilting the HS and causing uneven temps or perhaps I just did a crappy job on install.
Unfortunately I don’t have my OC notes in front of me at the moment but I believe my Bios VCore was set at 1.43v to achieve such an OC. Voltages any lower would result in a core failure in Prime95. So far having no issues with booting or blue screens. Vista Ultimate 64 with 4 gig Kingston HyperX mem.
3.6 is pretty much the upper limit on air cooling on a Q6600.
The core thing is differences in the two die... you have two E6600 dies pasted together. Anyways.. best way to average that out is lap the Heat sink and CPU. If you don't want to do that, you're at about the max you can go (as you've seen).