Design and analysis of arbitration protocols

Arbitration protocols are needed to prevent conflicts when several processors share a common resource. Five arbitration protocols, commonly used in digital systems, are modeled and their hardware implementations are discussed. The effect of the chosen protocol on the performance of the system, access time (delay before the bus is available) and data throughput (channel utilization efficiency) for each processor, can be studied using the models for these protocols. Four of the protocols considered are identified as being suitable for multiprocessor systems. It is shown that the rotating-priority protocol gives the best system performance. The fifth protocol, the unequal-priority protocol, is shown to offer the worst performance. This is because the protocol was originally intended for single-processor systems. Hardware schemes for the other four protocols are proposed. The schemes are decentralized and require a smaller number of communication lines between the processors. Live insertion and removal of processors from the system is possible since bus-status information is available to all processors at all times.<
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