FSB is quad pumped so you take the base speed and multiply by 4 when your taking about core 2 chips.
FSB=Base FSB x4
The CPU speed is the base speed times the multiplier
The FSB speed that matter with stock speed is 1333 which means you could go as low as ddr2 667 and not have a performance loss. (assuming you dual channel the memory the 667x2=1333)
The ratio allows the memory and the CPU to stay in sync. 1:1 is ideal. but if you ram is faster it will alter it so that the effective is 1:1. (can't figure an example right now.)
Long story short. at stock speed the slowest ram you can buy is ddr2 667 and if your ram is faster then your cpu then you will not expierence a performance loss, you will just not utilize your memory to it's fullest extent.
Thanks guys for your help, does that mean that fast ram (1066 onwards) effectively only helps when over-clocking? I mean, I dont think there are any chips from Intel that would be able to utilize ram @ 1066, 1333 or even 1600 when running at their stock speeds???
Yes 667 is slower then 1333. but keep in mind that memory is run in dual channel to double is speed. 667x2=1333
yes faster ram is only useful when overclocking. The next intel chip will use ddr3 and a triple memory bandwidth. So if your building now there is no real point in getting the faster memory. I would at least get ddr2 800. the extra bandwidth will help with small overclocks which are easy enough on most motherboards