CPU Clock Speed

The clock speed of a CPU is the speed at which it can potentially execute instructions. In older CPUs this was measured in millions of cycles per second or megahertz (MHz); more recent CPUs are so fast that they are measured in billions of cycles per second or gigahertz (GHz). A CPU of a certain type and model may be available in a range of clock speeds. All other features being equal, the CPU with the faster clock speed will be more expensive.
However when comparing different models of CPUs, the faster clock speed alone will not determine the fastest CPU. Manufacturers use a wide variety of technologies to speed up CPUs. For example, the number f clock cycles required for completing the same operation was vary between CPU models. To the end user, the perceived speed of a a PC, or lack of it, may involve other aspect of the total design of the compute, such as the ache size, the amount and speed of the RAM and the speed of the hard drive.