I have had a P5B deluxe with 3 different 4 sticks of memory configurations. every setup required tRCD and tRP at 5 or greater. That is the only change I need to make from the 2 to 4 memory stick configuration. Increased memory volts were needed for overclocking either 2 sticks or 4. It was the save volts requirement in either setup.
With 4 sticks you can try the TRFC at 35. But, for 4 sticks I have needed that set to 42.
I keep the others set at defaults. They are 10 and 11. I think that these setting are used by OEM when optimizing of the bios.
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http://www.chuckbam.com/101007/bench..._stability.htm