CPU FSB

Neither number is an accurate way to identify the amount of work a CPU does in a given time period. The only real way to judge is with benchmarks with real world applications. Generally a faster processor speed will, when judged with other processors of the same type, preform better. However when comparing different processor architectures this does not work.

At 2ghz Penryn Core > Conroe Core > Phenom > Athlon >> Pentium 4 Core.

The FSB mostly effects the amount of data that can be transfered between memory and the CPU. This will, most times, have less effect on performance than the processor speed. A 800 FSB CPU in a 1066 Chipset will run at the older 800 FSB speed. Make sure whatever chipset you use supports your processor. Many newer Intel processors will not work in older chipsets even if they have the same socket. (A 1066 fsb CPU will not work in a mother board only capable of a max 800 FSB). This is less of a problem with the AMD chipsets but I would still advise checking with the manufactures website.

Thanks for the advice, but I don't want to know what CPU is fastest etc.
I just want to understand what FSB means and how to calculate the speed of CPU.