FLEXBAR: A crossbar switching fabric with improved performance and utilization

Crossbar based switching fabrics form a critical component of many modern high-performance electronic systems, including network routers and switches, multi-processor computing systems, and high-end application-specific integrated circuits (ASICs). This paper describes a simple, yet effective, hardware modification to enhance the performance and utilization of a generic crossbar. The proposed structure, called FLEXBAR, is based on the addition of lightweight, configurable, input and output hardware layers that exploit unutilized switching paths to provide additional data transfer capability for highly loaded paths. FLEXBAR has been implemented and evaluated as a network switch fabric. Extensive system simulations under various traffic scenarios indicate that latency reduces by up to 70%, and peak throughput of highly loaded ports can increase by over 100%. A full-custom design of FLEXBAR in 0.35 micron technology requires marginal area and performance overheads (4.47% and 8.23%, respectively, for a typical configuration) compared to a conventional crossbar.