Originally posted here by nihil
Hi Jareds FSB = Front Serial BUS,
Ehhmm.. It's Front Side Bus.

http://www.computerhope.com/jargon/f/fsb.htm

It's the bus the processor uses to communicate with the rest of the hardware, IO and memory.
And yes, it's THE bottleneck (there are a few others like the PCI bus). This FSB bottleneck is the reason why there's first and second level cache on your processor.

Please explain how the 1000mhz FSB is the bottleneck if it's faster than all (readily) available RAM.
Because the processor runs 2-3 times faster then the fastest RAM available. They can make the actual RAM chips as fast as the processor (the cache in modern processors runs at the same speed as the processor) but the problem is in the connection between the processor and the memory.

This has to do with physics.. Electricity travels at about half the speed of light. With these extremely high frequenties, electrons can't travel fast enough to cope with the physical distance involved.