A comparison of Broadcast-based and Switch-based Networks of Workstations

Abstract

memory, fault tolerance. Networks of Workstations have been mostly designed using switch-based architectures and programming based on message passing. This paper describes a network of workstations based on the Simultaneous Optical Multiprocessor Exchange Bus (SOME-Bus) which is a low-latency, high-bandwidth interconnection network that directly links arbitrary pairs of processor nodes without contention, and can efficiently interconnect several hundred nodes. Each node has a dedicated output channel and an array of receivers, with one receiver dedicated to every other node's output channel. The SOME-Bus eliminates the need for global arbitration and provides bandwidth that scales directly with the number of nodes in the system. Under the Distributed Shared Memory (DSM) paradigm, the SOME-bus allows strong integration of the transmitter, receiver and cache controller hardware to produce a highly integrated system-wide cache coherence mechanism. Backward Error Recovery fault-tolerance techniques can exploit DSM data replication and SOME-Bus broadcasts with little additional network traffic and corresponding performance degradation. This paper examines switch-based networks that maintain high performance under varying degrees of application locality, and compares them to the SOME-Bus, in terms of latency and processor utilization. In addition, the effect of fault-tolerant DSM is examined on all networks. 1