a measure of the rate at which the main processor is being run, measured in MHz
The switching frequency of the clock circuit in digital logic. It is principally determined by the rise/fall time required for the digital devices used in a circuit to change logic state (from 0 to 1 or vice versa).
The changes in the cycle from one state to another within a computer system are timed using a pulse produced by a circuit called a clock. The unit of measurement for the number of complete cycles per second is the Hertz. Typical clock speeds range from 33 MHz to 2.5GHz.
The speed of the computer is measured by electronic circuits in an internal timing device.