Digital circuits

Most integrated circuits of sufficient complexity utilize a clock signal in order to synchronize different parts of the circuit and to account for propagation delays. As ICs become more complex, the problem of supplying accurate and synchronized clocks to all the circuits becomes increasingly difficult. The preeminent example of such complex chips is the microprocessor, the central component of modern computers, which relies on a clock from a crystal oscillator.

A clock signal might also be gated, that is, joint with a controlling signal that enables or disables the clock signals for a certain part of a circuit. This technique is often used to save power by efficiently shutting down portions of a digital circuit when they are not in use.

In some near the beginning microprocessors such as the National Semiconductor IMP-16 family, a multi-phase clock was used. In the case of the IMP-16, the clock had four phases, each 90 degrees apart, in order to synchronize the operations of the processor core and its peripherals. Most modern microprocessors and microcontrollers use a single-phase clock, however.

Many modern microcomputers utilize a "clock multiplier" which multiplies a lower frequency external clock to the suitable clock rate of the microprocessor. This allows the CPU to operate at a much higher frequency than the rest of the computer, which affords performance gains in situations where the CPU does not need to wait on an external factor.