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Aye, I have tried everything I can think of. I can get it to around 3.5 (tops) but it resets itself back to 2.4 anthing from a few hours or a few weeks later.
I upped the voltage, no difference. Changing the frequency to 101 helped a little I think though I can't be certain.
It's getting to the stage where I'll either book it in to a local computer shop to see what they can get out of it or I'll just eek out the 775 socket a while longer with a Q9650 or an 8600. Don't see the point of changing the motherboard at this point.
Are you sure it's your cpu that's letting you down and not your RAM? What do you have that set to?
As mentioned above 3.5GHz isn't bad for a Q6600, and you'd be unlikely to see much difference between that and a Q9650@4GHz apart from in benchmarks.
What RAM is it and what voltages are you chucking through it? Just because it passes memtest doesn't mean it won't fall over at some point. BTW you should ideally run memtest overnight giving it time to do several passes.
Just for your information, my Q6600 needed 1.4v to get to 3.6GHz and that was on a X38 board.
EDIT: Might be an idea to post your BIOS settings in here (vcore, ram voltages and timings, northbridge voltages etc etc), there might be somebody else who's running the same board that may be able to help.