Fear the mighty x58
I forgot what a pain it is to clock this board There just isn't enough granularity to fine-tune the memory frequency... I can only choose the CPU to be even numbered multiples of the BCLK, (22x, 20x, 18x) etc, and I can only choose 3x, 4x or 5x the BCLK for the memory frequency. For a 4Ghz CPU clock this pretty much puts me at 915Mhz (22x183 with "5x" mem multiplier as above).
The memory controller on the CPU seems to hit a hard wall at 950Mhz. I can boot up and run 32Mb pi at 950Mhz (3.8Ghz CPU) with 9-9-9-24, even on 1.4v. But at 955Mhz I can't even get into windows no matter the timings (even CAS11 with 1.65v it won't get into Windows). Tried adjusting all sorts of voltages, but nothing seems to dent to 950Mhz wall.
Anyway, so that's pretty much the frequency I have to run at - all that's left is to tweak the timings
Memory is Corsair XMS rated at 2000Mhz 9-9-9-24.
I will fire up my mighty X58 rig later and give it a blast.