what bios are you running simkin? air or water cooled? i'd say SPU PLL, FSBT, NB, voltages are important. hell, all are important. what i did is looked in the manual for the highest normal settings (except for DRAM) and set it to that. i worked my way back from there to find what was stable. that was for the 3.8 though. 3.9 was another story.