That's what he has, but I think what TechKnight is saying is that you can't just drop a faster CPU in.  Well, you could, but it wouldn't be any faster.  The new CPU would just be downclocked to whatever the crystal is set to.  If you change the crystal so you have a faster CPU, the other components that are dependent on that original crystal operating at its original frequency will fail.

So to avoid that, you only change the line that's in charge of the CPU speed, and put a doohickey in so you can change the frequency without changing everything else.