Megahertz myth

While clock rates are a valid way of comparing the performance of different speeds of the same model and type of processor, other factors such as an amount of execution units, pipeline depth, cache hierarchy, branch prediction, and instruction sets can greatly affect the performance when considering different processors.

Similarly, at this time the Intel 80486 was selling alongside the Pentium which delivered almost twice the performance of the 80486 at the same clock rate.

[2] The myth arose because the clock rate was commonly taken as a simple measure of processor performance, and was promoted in advertising and by enthusiasts without taking into account other factors.

[5] From approximately 1995 to 2005, Intel advertised its Pentium mainstream processors primarily on the basis of clock speed alone, in comparison to competitor products from AMD.

This continued up until about 2005, when the Pentium Extreme Edition was reaching thermal dissipation limits running at speeds of nearly 4 gigahertz.

Several years' advances in manufacturing processes and power management (specifically, the ability to set clock speeds on a per-core basis) allowed for clock speeds as high or higher than the old NetBurst Pentium 4s and Pentium Ds but with much higher efficiency and performance.

In June 2013, AMD released the FX-9590 which can reach speeds of up to 5.0 GHz, but similar issues with power usage and heat output returned.