Electronic – CPU and clock rate

clockclock-speedcpu

As I understand it, CPUs generate electrical pulses using a quartz crystal. The rate the pulses are generated (taking into account various multipliers) give the processing speed which all components run off (2, 3, 4 GHz etc).

Does this mean that these electrical pulses drive all the components in the CPU? i.e. is the clock rate the input of electricity for the CPU where transistors are switched on and off (potentially) at the clock rate? So a clock rate of 3GHz means that transistors can be switched on and off 3 billion times a second? Or have I interpreted it wrong?

Also, when the quartz crystal generates this electrical pulse, what happens to it exactly and what does it do?

Best Answer

Actually, the clock cycle wont tell the speed at wich a single transistor can switch, but, how much time it does take for a signal to travel the slowest/longest path. A single cmos transistor on a modern cpu can switch at speeds much higher than the clock used on the cpu, but, the clock is not based only on transistor switching speed but on signal travel times. Thats the whole point of dividing the cpu into shorter stages (pipelining), to decrease the length that the signal must pass before finishing the execution of a certain task. That length versus speed of electron flow will determine the longest propagation delay and so will limit the max clock of the system.