you don't have to worry about that with AMD64s, with PC3200 it's a 1:1 ratio by default (meaning CPU and RAM communicating at the same speed)
it was only back in the XP days when CPUs were 266FSB, 333FSB, and 400FSB that you had to worry...AMD64s don't technically use FSB anymore but they are basically '400FSB' (I only use that as a reference to show you what I mean)
400FSB = DDR400 (PC3200) which = 1:1