CPU busses

I heard that the busses a standard pc has, are 400mhz fast. My computer has a 100mhz external clock (I believe it is called) speed. From what I understand, it means that although the busses support a much faster speed, my computer isn't able to utilize it. How much does that matter? what are those busses connected to? Isn't my RAM connected directoly to my motherboard? Aren't busses connected just to my hard drive and CD-Roms?

Bus is just a generic term for some data transport mechanism. The bus you're referring to about your CPU is called the FSB (Front-Side Bus). Its the speed at which your motherboard can communicate with the CPU.
The higher the bus speeds, and, the wider the bus (i.e. 64bit v 32bit) the higher the data throughput.

Thanks :)

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Originally posted by Blacknight
My computer has a 100mhz external clock

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Because most FSB are quad-pumped, you have a 400MHz FSB also, but it is truly only 100MHz, and it sends 4 times the amount of information each cycle.