The Return of Asynchronous Logic

Introduction Asynchronous logic is enjoying a resurgence of interest and is poised to resume a role in commercial electronics which it has not played for a few decades, despite its use in some of the earliest computers. For the last twenty years electronic design has been dominated by the use of clocks to control communication and state transitions. The clock, like the conductor of an orchestra, keeps all parts of the system synchronized. However, while synchronous operation is essential to the correct functioning of an orchestra, it is not central to the operation of an integrated circuits. An integrated circuit is more like a production line where maintaining a smooth flow of partially completed products is important, but achieving this by forcing exact synchrony throughout the production line is unnecessarily rigid. There is no doubt that the clock offers a simple control model, as a result of which electronic design has been able to keep pace with and exploit rapid advances in technology. So why should we contemplate discarding the basis of the design methodology which has been so successful?