JH68,
Exactly, what cpu do you have? If it's a P4 2.53/533fsb, then the bios set by hardware option will read 133, the default. If it's a P4 2.5/400fsb, then it will read 100, the default.
Since the GA-8IHXP is a i850E board, a P4/533fsb cpu works best. A P4/400fsb cpu actually works better & OCs better with a i850 board (e.g.AbitTH7II). Note that the 2 chipsets work correctly with different rdrams, i850E/16 bit pc1066/800rdram or i850/16 bit pc800/400rdram.
Your choice of rdram you use with the GA-8IHXP is important & is the limiting factor in overall performance. Best to use only 2 slots with rdram modules & the other 2 with crimms. EasyTune utility is of no real value & best not installed.
If Ocing is your interest, the 2.53/533 cpu is a poor OCer. The 2.2/400 & 2.8/533 are great OCers. Have used both boards mentioned above with various cpus extensively.