A Comparative Throughput Analysis of Scalable Coherent Interface and Myrinet

It has become increasingly popular to construct large parallel computers by connecting many inexpensive nodes built with commercial-off-the-shelf (COTS) parts. These clusters can be built at a much lower cost than traditional supercomputers of comparable performance. A key decision that will greatly affect the overall performance of the cluster is the method used to connect the nodes together. Choosing the best interconnect and topology is not at all trivial since performance and cost will change as the system size is scaled. This paper presents throughput models used for the analysis and comparison of performance in two leading System Area Networks (SANs), Myrinet and Scalable Coherent Interface (SCI). First, analytical models for throughput are developed by determining the theoretical bandwidth of all internal buses and links that are part of the interconnect architecture. Then, experiments are conducted to measure the actual bandwidth available at each of these components, and the models are calibrated so they accurately represent the experimental results. Finally, the models are used to compare the maximum throughput of Myrinet and SCI systems with respect to system size and overall dollar cost.