Inside parallel computers: trends in interconnection networks

Computational scientists who depend on parallel computing to let them run larger models in less time will be disappointed unless the processors can pass information back and forth quickly. The interconnection networks through which processors communicate in tightly-coupled parallel machines thus remain a vital research topic for computer architects. Over the last two decades, we have seen an evolution in the demands placed on these networks. Early SIMD machines required the simultaneous transfer of data from each network input to each output for a relatively small set of communication configurations or permutations; whereas the SIMD and MIMD machines of today need to support varied patterns of synchronous and asynchronous traffic, respectively. Interconnection networks can be categorized according to a number of criteria such as topology, routing strategy and switching technique. They vary widely in their cost, fault tolerance, simplicity, amenability to partitioning, and their aggregate bandwidth for local and nonlocal traffic patterns.