FastTrackNoC: A DDR NoC with FastTrack Router Datapaths

This paper introduces FastTrackNoC, a Network-on-Chip router architecture that reduces latency by bypassing its switch traversal (ST) stage. FastTrackNoC adds a fast-track path between the head of a particular virtual channel (VC) buffer at each input port and the link of the opposite output. This allows non-turning flits to bypass ST when the required router resources are available. FastTrackNoC combines ST bypassing with existing techniques for reducing latency, namely, pipeline bypassing of control stages, precomputed routing and lookahead control signaling, to allow at best a flit to proceed directly to link traversal (LT). FastTrackNoC is applied to a Dual Data Rate (DDR) router in order to maximize throughput. Post place and route results in 28nm technology show that (i) compared to the current state of the art DDR NoCs, FastTrackNoC offers the same throughput and reduces average packet latency by 11-32% requiring up to 5% more power and (ii) compared to current state of the art Single Data Rate (SDR) NoCs, FastTrackNoC reduces packet latency by 9-40% and achieves 16-19% higher throughput with 5% higher power at the SDR NoC saturation point.