P67 Asus Sabertooth B3. I have been able to run it at 1866 but it was unstable even at 2T timing or when I loosened the timing manually. Selecting a profile of anything above 1866 and no boot. The XMS3 is also rated at 1.65v although I am able to run mine OK at 1.55v @ 1600 on the stock timings. When I plugged in a pair of Mushkin, I simply selected the 2133 profile and bammm, boots fine at low volts and my bench scores improved straight away. I get the impression that RAM designed to run at 1.5v is better suited to SB setups. Carl