Thanks Kavin, yeah cpu could determine what voltages memory needs, so far 2x i7 920 c0 and 1x i7 920 d0 all require me to have 1.65v vdimm for GT at 2000mhz 7-8-7-20.

Guys just remembered one thing, for my Win7 setup in bios power management I have HPET support enabled and set at 64bit. Not sure if it that is what is allowing me 21x Turbo without problems. Worth a try