Well I am using a XFX 790i Ultra with E8400 and A-DATA DDR3 1600. The memory will do 1800Mhz CL7 at 2V and the CPU works perfectly fine on good air at 4.05 GHz (450 MHz).

When using the P04 BIOS from XFX, the board runs fine at 400 MHz (3.6 ghz), stable. I can easily boot at 450 MHz and I know the memory works flawlessly at this speed (benched on P5K3 Deluxe). But I won't be able to format the HDD for Windows Install at this speed, and after installing windows at 400 MHz FSB and then raising it back to 450, I get corruption after boot. The shipping bios of the board was riddled with bugs. Even very noticable ones (tried setting CL7-7-7 in the bios always ended up with CL8-7-7 for example) those seem fixed by P04. Oh and setting 1T or 2T does not change anything in my case.

I will try to tweak the settings as mentioned. I was aiming for those 4+ Ghz on air...

cheers
DS