I have the P5Q pro stable at 8.5x500 with an E8400 on bios 0901. Basically at first no amount of tweaking could get 500mhz stable it would constantly BSOD but I upped the cpu voltage to 1.4v and it was rock solid stable but what was weird is that it would need 1.4v even at 6x500 the high FSB needs the cpu volts unlike my P35 board.