To be stable at 4 GHz or above I had to increase these voltages:

IOH/ICH 1.1V Voltage: 1.27v
IOH Analog Voltage: 1.25v
ICH 1.5 Voltage: 1.7v

Caught them in this thread http://www.xtremesystems.org/forums/...d.php?t=214381. They seemed to do the difference in stability. 20 x 200 seems impossible for me though. Using 21 x 192 atm. I have a vcore of 1.45 and VTT of 1.4.

For a 200 bclk I need VTT of 1.5 or above to post, this feels like a little too much for 24/7 use..