This paper examines the performance of distributed-shared-memory (DSM) systems based on the Simultaneous Optical Multiprocessor Exchange Bus (SOME-Bus) using queuing network models and develops theoretical results which predict processor utilization, message latency and other useful measures. It also presents simulation results which compare the performance of the SOME-Bus, the crossbar and the torus using queuing-network models. The SOME-Bus is a broadcast-based, fiber-optic interconnection network which contains a dedicated channel for the data output of each node, eliminating the need for global arbitration and providing bandwidth that scales directly with the number of nodes in the system. The effect of collective communications due to cache coherence is examined. Results reveal that the performance of the SOME-Bus interconnection network is the least affected by large communication times, compared to the other two architectures considered here. Even in the presence of intense coherence traffic, processor utilization and message latency is much less affected than in the other architectures.