The following text is excerpted from an article on the web about CPU performance.

"The total clock speed or CPU performance of a device indicates how many processing cycles per second can be executed by a CPU, considering all of its processing units (more commonly referred to as cores). The CPU speed is measured in gigahertz (GHz), with each gigahertz being equivalent to one thousand million cycles per second. Given the same clock rate, more CPU parallelism can contribute better performance. However, power dissipation and circuit temperature usually constrain modern processors clock frequency and thus they can be dynamically changed so that circuit temperature stays below a certain limit.

When considering the total CPU speed, let us look for more GHz and a higher core count. Although this is not the single determining factor for an electronic device's performance, high processor speed is crucial if you are looking to perform demanding tasks such as gaming or video editing. As for the core count, a CPU chip with multiple processing units has the advantage of being able to run various tasks at the same time.

Nowadays, a CPU chip can comprise cores with varying speeds, thanks to ARM's big.LITTLE technology; the advantage is that tasks are assigned to different cores depending on how demanding they are, optimizing system usage, and preventing overheating. For instance, sending e-mails doesn't require much processing power. Instead of assigning this task to a sophisticated core, the system will delegate these tasks to LITTLE cores that produce less heat than the BIG cores with an aggressive execution such as multi-issue pipelines, hardware multithreading or out-of-order execution. Besides, even a single-core may be able to operate on different clock speeds: namely "base" and "turbo."

The current victor when it comes to total clock speed for computers is AMD's Epyc 7742, flaunting an overall clock rate of 64 x 2.25GHz (64 cores with 2.25 GHz each). The fierce competition among manufacturers means that higher CPU performance is a never-ending race."