Whether it is a laptop or a desktop, any computer is made up of several pieces of hardware that communicate with each other. Sending data back and forth to ensure that the user gets the desired results.

I have seen some theoretical stuff on computers & hardware, but I wonder how it all comes together.

• CPU
• RAM
• Graphics Card
• L1 CACHE
• L2 CACHE
• L3 CACHE
• FSB
• ...

And all other things. Which is the biggest bottle neck? Why would a person not want/need a big value in one of those categories in certain situations?

P.S.: when reading the specs of the i5 750 processor, I came across this description:

In place of the FSB, one or more high speed, point-to-point buses called Quick Path Interconnect (QPI) are used, formerly known as Common Serial Interconnect Bus or CSI. QPI features higher bandwidth than the traditional FSB and is better suited to system scaling.

What is this, and how does it compare to FSB?

EDIT: I am not planning to buy a computer at all. The goal of this question is to understand the internal relation of various hardware pieces, their specific functions and how they work together.

For instance, I have heard to a somewhat higher-than-usual amount of L2/L3 Cache can help speed up your computer. What's up with saying that? Also I forgot to mention Hard-disk RPM.