Comparison of Mesh and Hierarchical Networks for Multiprocessors

Upper bounds on message delay and throughput are developed for two networks that have been used in recent multiprocessor systems. Two-dimensional mesh networks with bidirectional links and no end-around connections are compared to bus-type hierarchical networks that use segmented rings for the interconnection paths at each level of the hierarchy. Wormhole routing of short, fixed-length messages is used in the mesh networks, while a complete message can be switched between ring segments in one switch time in the hierarchical networks. It is found that three-level hierarchical systems perform somewhat better than mesh systems with respect to the basic bounds criteria that are developed.