855 maxes out at PC2700. If you use PC3200, you can get a percent or two faster because you can run it at lower latencies than typical PC2700 memory. (The fastest notebook memory I've found is still CL2.5; you can run PC3200 CL2.5 at PC2700 CL2 though.) Also if you're going to overclock the CPU then your memory bus speed will raise too. In that case, using PC3200 will let you overclock without worrying about the memory struggling to keep up.
6/15/05 at 5:15pm