fsb

I have a duo-core motherboard that supports FSB speeds of 533 mhz, 800 mhz and 1066 mhz. My CPU is rated at 800 mhz. I'm using DDR2-4200 memory which is 533 mhz. My question is does my FSB run at both speeds or must it "dumb" down the CPU to the lowest speed? Also, if I were to get...