I've just attempted to rebuild my rig with the Sabertooth X58, i7950 and 6gb of Corsair XMS3 memory. I've had a few strange problems with the system not posting, but after fiddling around and resetting the CMOS a few times i've gotten that to work.
My issue now is that the bios is only recognizing 4gb of memory, which I understand is a pretty common issue (although oddly, CPU-Z reports the full 6gb). After playing with the manual memory settings a bit and shuffling things around, I'm to the point where i'm pretty convinced the issue is with my heatsink pressure.
I've got the Venomous X and when I installed it, I thought it was odd that I had to remove to locking bracket from the board in order to install the backplate. So now, anytime I remove the pressure plate to remove the heatsink, the processor just comes right off, stuck to the bottom with thermal grease. Is this okay?? Seems to me like it could be part of my problem, my only other alternative at this point seems to be just monkeying with quarter turns to see if the pressure really is the issue.
Took a couple days to sort out 'cause I was too lazy to pull everything out right away. After taking everything out I replaced the motherboard bracket that allows the CPU to be locked into place. I also realized i had the extra square spacer bit in the middle of the backplate, so I removed that and put some thin nylon spacers from Ace Hardware on the backplate screw posts. Threw everything back together and it all works like a dream now, all 6gb recognized.