The Vtt suggested by Intel is way off. Additionally, in order to run a larger ammount of RAM, you will need to up your Vtt. Call your RAM manufactuerer and they should clear this up for you. I run my i7 860 at 1.41V Vtt. If I am overclocking at 4GHz anything less than 1.25V will BSOD on me and anything less than 1.2 won't even boot.