How are clock rate measured and what does it mean?

After some Wiki researches about clock rate, I find two question:

1. What does a cycle mean?

2. How does a cycle affect the processing speed?

Sorry for being a noob.... But really hope someone can answer my question, Thank you

What does a cycle mean?

Clock is a signal used to sync things inside the computer. Take a look at Figure 2, where we show a typical clock signal: it is a square wave changing from “0” to “1” at a fixed rate. On this figure you can see three full clock cycles (“ticks”). The beginning of each cycle is when the clock signal goes from “0” to “1”; we marked this with an arrow. The clock signal is measured in a unit called Hertz (Hz), which is the number of clock cycles per second. A clock of 100 MHz means that in one second there is 100 million clock cycles.

In the computer, all timings are measured in terms of clock cycles.

Source Clock

How does a cycle affect the processing speed?

To think that clock and performance is the same thing is the most common misconception about processors.

If you compare two completely identical CPUs, the one running at a higher clock rate will be faster. In this case, with a higher clock rate, the time between each clock cycle will be shorter, so things are going to be performed in less time and the performance will be higher. But when you do compare two different processors, this is not necessarily true.

If you get two processors with different architectures – for example, two different manufacturers, like Intel and AMD – things inside the CPU are completely different.

As we mentioned, each instruction takes a certain number of clock cycles to be executed. Let’s say that processor “A” takes seven clock cycles to perform a given instruction, and that processor “B” takes five clock cycles to perform this same instruction. If they are running at the same clock rate, processor “B” will be faster, because it can process this instruction is less time.

For modern CPUs there is much more in the performance game, as CPUs have different number of execution units, different cache sizes, different ways of transferring data inside the CPU, different ways of processing the instructions inside the execution units, different clock rates with the outside world, etc.

Source Clock

Further reading

• How a CPU Works