palladin9479 :
Yep, like all things Silicon has a finite limit. It's as I said, the absolute speed limit for a given material is based on how fast an electron can move through it. Faster your electrons move the shorter the time between signal generation and signal reception, aka signal propagation. The shorter that time the more signals can be sent per unit of time measurement, aka clock speed.
The electron speed has very little to do with it, electrons move very slowly. In semiconductors they barely move at all
http://en.wikipedia.org/wiki/Drift_velocity
Electric fields on the other hand move extremely quickly (speed of light in a vacuum, just below that in unshielded wire, significantly lower in shielded wire). Imagine a crowded expressway, everyone wants to get home so everyone's trying to move forward. If one car exits the expressway then we can use the driver's anger to gauge how bad the traffic is. We can also assume that as one car leaves, another enters. Thus, for a signal to pass from one point to another the carriers themselves need not move the entire distance, only enough that the information itself be carried.
Electromagnetic waves function very similarly to material waves. If you wave a skipping rope up and down each point on the rope only ever moves up and down, but the material pushes and pulls on the material next to it which is in turn moving up and down. This is how a wave travels down a rope, in a pool, and in an electrical wire. It's also the reason why DC power is horrible for long distance transmission.