Clock Speed: Difference between revisions
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This is because clock speed is not actually a measure of performance in itself. The clock simply synchronises the different components within the CPU so that everything operates in proper order. The higher the clock speed, the more quickly these components operate.
== Instructions and Design ==
The design of the components themselves is another matter. CPUs perform operations called 'instructions' on data to get results; some operations take multiple cycles to perform, others can be performed multiple times in a single cycle. Exactly how fast it can do these varies between CPU types. In the example above with the Pentium and Core, the Core is faster because it does more operations (more ''work'') per clock cycle than the Pentium does.
When you put the clock speed together with the operations per cycle, and the 'bit size' or data word length, you get a fairly decent estimate of performance. Measuring performance based on clock speed alone is usually referred to as the "megahertz myth," generally by companies competing with Intel.
== Latency ==
Also, a processor cannot just move instantly from one clock cycle to the next. There is a lag between them, called latency. This is an issue with processors, but even more with RAM, which also has a clock speed. Latency means that there is a pause, when a component does nothing. It's the digital equivalent of inertia, and gets worse with poor hardware synchronization, because data has to sit and wait for components to open up for it. It's usually a microscopic fraction of a second, but with dynamic programs like video game graphics, latency cannot be ignored. High latency parts are either best left out of the system, or reserved for processing that doesn't involve graphics (physics, AI, and others).
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== Clockless CPUs ==
Therefore, clockless CPUs are mostly prototypes, none have been mass-produced for desktops or even cell phones yet. x86, ARM, and PPC (in that order) remain by far the most likely CPUs an end user will deal with.
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