New Santa Rosa Machine, 800MHz FSB but only 667MHz mem controller?

I'm a little confused about my new MacBook Pro...its got a Santa Rosa chipset (Intel PM965), which has an 800MHz FSB, but the mem controller only supports DDR2-667? Why isn't it running 1:1? I'm coming from the AMD world, and I realize that running asynch in the Intel world isn't as big of a deal as in the AMD world, but I still don't understand why they did that...

I am not familiar with that system but can you gives us the exact specs of the system? cpu, etc?

But in the Intel world 800MHz means 200MHz (quad pumped) = 4 x 200MHz = 800MHz FSB. So with a 1:1 memory ratio your memory would be running at (400MHz) DDR2-400. If your memory is set to a memory multiplier of 5/3 (not sure if it is possible) then (2 x 200MHz) x 5/3 = 667MHz it could technically be running at 667MHz (DDR2-667).

You say that the memory supports DDR2-667 but it doesn't necessarily mean it is running at this speed.

yeah, as GTengineer said, intel FSB is quad pumped, Ram is only doubled.

So 200 FSB = 400Mhz ram
333 FSB = 667hmz ram
400 FSB = 800Mhz ram
(at 1:1)
your running 3:5 ratio right now

im waiting for a pm965 mini-itx or matx board so i can get a few of those... 35 tdp dual cores..hmm tasty for some low power folding action.

well some santa rosa's do 800mhz ram ... like mine i think does 800mhz for 2 gigs but if you put in 4 gigs then it drops to 667 ...