|kuwese's answer is correct. You should always reduce the advertised speeds down to their actual frequencies to make proper comparisons.|
Since you mentioned FSB, you're probably asking about an Intel system. For best performance, the CPU:DRAM frequency ratio should either be 1:1 or 1:2. In other words, CPU freq at 200MHz & RAM freq at 200MHz, or CPU freq at 200MHz & RAM freq at 400MHz.
If you leave your settings at their defaults, your ratio would be CPU freq at 200MHz & RAM freq at 533MHz, which is a approx 3:8. That leaves you with two choices...1.) overclock the CPU to 266MHz freq (1066MHz FSB) to hit 1:2, or 2.) underclock the RAM to 400MHz (800MHz DDR) to hit 1:1.
Hopefully you don't have a P4 because the above ratio theory does not apply.