Editing Clock rate (section)

== Comparing ==
{{main|Megahertz myth}}
The clock rate of a CPU is most useful for providing comparisons between CPUs in the same family. The clock rate is only one of several factors that can influence performance when comparing processors in different families. For example, an IBM PC with an [[Intel 80486]] [[Central processing unit|CPU]] running at 50&nbsp;MHz will be about twice as fast (internally only) as one with the same CPU and memory running at 25&nbsp;MHz, while the same will not be true for MIPS R4000 running at the same clock rate as the two are different processors that implement different architectures and microarchitectures. Further, a "cumulative clock rate" measure is sometimes assumed by taking the total cores and multiplying by the total clock rate (e.g. a dual-core 2.8&nbsp;GHz processor running at a cumulative 5.6&nbsp;GHz). There are many other factors to consider when comparing the performance of CPUs, like the width of the CPU's [[Bus (computing)|data bus]], the latency of the memory, and the [[CPU cache|cache]] architecture.

The clock rate alone is generally considered to be an inaccurate measure of performance when comparing different CPUs families. Software [[Benchmark (computing)|benchmark]]s are more useful. Clock rates can sometimes be misleading since the amount of work different CPUs can do in one cycle varies. For example, [[superscalar]] processors can execute more than one [[Instructions per cycle|instruction per cycle]] (on average), yet it is not uncommon for them to do "less" in a clock cycle. In addition, subscalar CPUs or use of parallelism can also affect the performance of the computer regardless of clock rate.