I've been running with pretty low Ram sub volts 0.82v compared to 0.90v (normal per bios) at 1.80v base so 45.50% of vdimm however > 1150Mhz you need to start cranking it up to around the 50% mark. found +100ps clock skew on channel A & -100ps on B seems to help a bit. Evas idea on Rank timings
Quote Originally Posted by Eva2000
Setting the 4 subtimings listed here to the following also helped stablise memory clock at 640mhz 5-5-5-15 at 2.56v

* Trd2rd(Different Rank).: 10
* Twr2wr(Different Rank): 9
* Twr2rd(Different Rank): 9
* Trd2wr(Same/Diff Rank): 10
from 5:6 Memory Divider (2.40B) + MCH Tweak Testing