Asynchronous circuit
An asynchronous circuit is a circuit in which the parts are largely autonomous. They are not subject to a central clock circuit, but instead need only wait for the components used in the current instruction/operation. This is contrasted in a synchronous circuit in which all parts of the circuit are operational and drawing power, even if not used for the current instruction/operation.
Asynchronous circuits offer several benefits over synchronous circuits, including avoiding clock skew and being (typically) less noisy. However, asynchronous circuits are more susceptible to the metastability problem.
Quotes
- "Asynchronous inputs are at the root of our race problems." -- D. Winker and F. Prosser
- "Having spend untold hours debugging digital designs, I can assure you that metastable behavior is a real problem, and every digital designer had better understand it" -- Bruce Nepple 1998-12-31