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In computer architecture, clock gating is a popular power management technique used in many synchronous circuits for reducing dynamic power dissipation, by removing the clock signal when the circuit, or a subpart of it, is not in use or ignores clock signal. Clock gating saves power by pruning the clock tree, at the cost of adding more logic to a circuit. Pruning the clock disables portions of the circuitry so that the flip-flops in them do not switch state, as switching the state consumes power. When not being switched, the switching power consumption goes to zero, and only leakage currents are incurred.[1]
Although asynchronous circuits by definition do not have a global "clock", the term perfect clock gating is used to illustrate how various clock gating techniques are simply approximations of the data-dependent behavior exhibited by asynchronous circuitry. As the granularity on which one gates the clock of a synchronous circuit approaches zero, the power consumption of that circuit approaches that of an asynchronous circuit: the circuit only generates logic transitions when it is actively computing.[2]