The FSB is pretty much the FSB. However, for your CPU, as long as your motherboard's BIOS can identify the CPU (there are cool identifiers within the CPU that tell the BIOS what CPU it is), the FSB will be automatically configured to your CPU.
Overclocking is when you increase the FSB a bit. Or more than a bit. You can also, and this is what I think you are talking about, set your CPU FSB higher than your RAM FSB. This is what is called an asynchronous FSB.
My personal opinion: Don't mess with Async. It often makes your computer run slower rather than faster.
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