Arbiter (electronics)

Arbiters are electronic devices used in asynchronous circuits to order computational activities for shared resources; they prevent two operations from occurring at once when they should not. They are required in computers which have multiple CPUs or other devices accessing memory, and have more than one clock. It is then possible for requests from two unsynchronized sources to come in at nearly the same time. "Nearly" can be very close in time, in the sub-femtosecond range. The memory arbiter must then decide which request to service first. Unfortunately, it is not possible to do this in a fixed time.
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