The speed of a computer processor, or CPU, is determined by the clock cycle, which is the amount of time between two pulses of an oscillator. Generally speaking, the higher number of pulses per second, the faster the computer processor will be able to process information. The clock speed is measured in Hz, often either megahertz (MHz) or gigahertz (GHz). For example, a 4 GHz processor performs 4,000,000,000 clock cycles per second.
Computer processors can execute one or more instructions per clock cycle, depending on the type of processor. Early computer processors and slower CPUs can only execute one instruction per clock cycle, but modern processors can execute multiple instructions per clock cycle.