I just built a Core i7 920 system. And I went for a less expensive motherboard, the Asus P6T. It's in a case that has lots of ventilation, it's a Coolermaster HAF 932. And it seems stable at 18x200~ 3.6GHz. Mind you this CPU is not one of the D0 stepping cores, but it's not requiring extra voltage and it's running fairly cool.
Now I still need to do some real stability testing. But if it will do this speed on air cooling, I'll be a happy camper!
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I'd love to build a Phenom II, with a 790FX board. And compare the two systems head to head. But I can't afford to do that!