I run 400FSB 2:3 for DDR2-1200 @2.3v cas 5 on the DFI P965-S. I can't get board to do over 509FSB stable. 515FSB would be ideal which is why I'm considering the P35-Pro. Aren't you using crucial 8500's? What are your genie bios settings for the 515FSB along with voltages?