Although I have not been able to stabilize my system this post is great since I'm a noob and I can understand it better than many other guides! Thank you!

I am trying to get my 950 D0 (X58 FTW3) to run at 4.0Ghz (20x200) with 6GB(3x2) XMS3s  (supposively rated at 7-8-7-20-1T)
my CPU Vcore is at 1.2875 (my CPU temp goes up to 72C with prime95 during 30 mins of testing and I've heard my limit is 75 so I dont think I can go higher.) DIMM V:1.65, VTT V: 50mv

I set my timings to 7-8-7-20-74-1T tried both setting the uncore to 16x and also leaving it on auto, and memory ratio of 2:8.

Every time I run memtest I am getting errors. Do you guys know what do I need to tweak or if my CPU vcore is killing me? any information at all to try to stabalize this machine. I have another set of XMS3s which I am going to try to see if the sticks could be the problem and report back.

Thank you!!!

Ok, thank you for replying :) i tried what you told me and the errors kept happening so i switched all three modules to the other 3 which are supposed to be exactly the same kit but instead of the newer v8.2a they were v5.11a and i left everything at 78720741T and it ran 2 full passes without errors :D i did not touch my voltages vtt stayed at 50mv cpu core same v and vdimm at 1.65. Seems like one of the newer sticks might be faulty or need more juice than normal as your theory stated. Thank you for helping me work this problem out!

Question: if i wanted to overclock my cpu to 4.2 without increasing the ram and leaving it as it is, what would i have to set the ratio, cpu host freq, and uncore to? Im assuming these are the only values i would have to tweak. Is this correct?

Again, thank you!

Thank you so much for this.  This was exactly what I wanted to know in my post @ the SR2 section!  Cudos to you brother!

I just wanted to thank you for this great guide.
It sure helped me out...i am now running my mem at 2000mhz, instead of the 1540mhz, thanx to your simple explanation.
 
Claude