The influence of VLSI technology on the construction of distributed computing systems composed of hundreds of computers is investigated. After a review of Project X-tree, the concept of a modular communications domain to carry the inter-processor message traffic is introduction and analyzed. A separation of the switching circuitry from the user processors permits communication and computation to take place concurrently. It also provides the flexibility to match the network topology to a particular application and facilitates the construction of heterogeneous networks.

A design is presented for a set of VLSI building blocks that permit the construction of high-bandwidth networks of arbitrary topology, providing the modularity needed for incremental expansibility. The proposed VLSI switching components support message-based, virtual circuit communications over dedicated, time-multiplexed links. The simplest representative is the Y-component, a message switch with only three ports. Its usefulness for the construction of a variety of networks is shown with the analysis of simplified models. Some simulation results are presented that corroborate these findings.




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