The other issue of number of modules is an am64 problem. With san diego (ie FX, Opterons and 3700 / 4000) and venice (3000, 3200) cores, which are the newest ones, you are limited to EITHER 2 sticks of ram at full ddr400 1T speeds, or 4 sticks at ddr400 2T. Its just a limit on the meory controller, since the p4s don't have onboard controllers it isnt an issue for them.
If you could find 4 sticks of SINGLE sided ram (most are double, in fact pretty much all) then 4 sticks would work at 1T.
btw I didnt mean "what are you talking about" as if you are crazy, rather that if there was a specific reason (ie you wanted a new pc, or switching to intel) then I could give a more specific reply see.
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