Comparison of Multiplexing Schemes for Wormhole-Routed Networks

Time multiplexing and demand multiplexing are two ways to share a physical channel in wormhole routed networks which use multiple virtual channels. Message latency with time multiplexing is higher than with demand multiplexing but the former has the advantage of requiring less complex and expensive hardware. Thus the magnitude of the performance difference between the two is critical in deciding which approach to use in a cost-eeective network. In this paper we compare the performance of time and demand multiplexing using a simulation based approach. We show that demand multiplexing consistently out-performs time multiplexing{the improvement in message latency varies from 20% to 100% for representative traac patterns and for a variety of routing algorithms on a mesh architecture.