Asynchronous Bypass Channels: Improving Performance for Multi-synchronous NoCs

Networks-on-Chip (NoC) have emerged as a replacement for traditional shared-bus designs for on-chip communications. As with all current VLSI design, however, reducing power consumption in NoCs is a critical challenge. One approach to reduce power is to dynamically scale the voltage and frequency of each network node or groups of nodes (DVFS). Another approach to reduce power consumption is to replace the balanced clock tree with a globally-asynchronous, locally-synchronous (GALS) clocking scheme. NoCs implemented with either of these schemes, however, tend to have high latencies as packets must be synchronized at intermediate nodes between source and destination. In this paper, we propose a novel router microarchitecture which offers superior performance versus typical synchronizing router designs. Our approach features Asynchronous Bypass Channels (ABCs) at intermediate nodes thus avoiding synchronization delay. We also propose several new network topology and routing algorithm that leverage the advantages of the bypass channel offered by our router design. Our experiments show that our design improves the performance of a conventional synchronizing design with similar resources by up to 26% at low loads and increases saturation throughput by up to 50%.