start with a Vtt 0.02-0.04v above Vcore or so, set the NB ref to 0.63x, CPU ref to 0.65x, and Vnb will vary depending on strap, performance level and mem divider generally. From here once you get a baseline for yourself and find out what the minimum Vnb and Vcore you can work with is, lock Vnb down a step or two above minimum and setup NB ref, once you've got that merry, then CPU ref should nearly fall into place once you lock down a solid Vcore. You'll probably need to go up or down a few steps on Vtt till you find where it's most comfortable thanks to Asus minimalist gtl adjustment on the RF