Decomposed Arbiters for Large Crossbars with Multi-Queue Input Buffers

Crossbars are key components of communication switches used to construct multiprocessor interconnection networks. For a fixed number of nodes, larger crossbars result in reduced probability of conflicts and allows packets to traverse the network in fewer hops. However, increasing the size of the crossbar also increases the delay of the arbiter used to resolve conflicting requests. The increased arbitration delay can lead to overall poor network performance. The impact of the increased arbitration delay can be mitigated by decomposing the arbitration process into multiple steps, such that some requests can be granted before the arbitration of the entire crossbar is complete. This paper deals with the design of such decomposed arbiters for large crossbars. The focus is on crossbars with multi-queue buffers at their inputs. Such buffers have been shown to provide significantly higher performance than conventional FIFO buffers.