DyAD - Smart Routing for Networks-on-Chip

The performance of Networks-on-Chip (NoC) is highly dependent on the throughput and latency properties of the on-chip routers. Deterministic routing gives better latency at low packet injection, however, the performance degrades quickly when the network becomes congested. Compared to deterministic routing, adaptive routing alleviates the congestion problem at higher packet injection rates by distributing packets across multiple routing paths. However, it suffers from higher latency at low injection rates due to the extra logic needed to perform the routing path selection. In this paper, we present and evaluate a novel routing scheme called DyAD which combines the advantages of both deterministic and adaptive routing schemes. More precisely, we envision a new routing technique which judiciously switches between deterministic and adaptive routing based on the network’s congestion conditions. The simulation results show the effectiveness of DyAD by comparing it with purely deterministic and adaptive routing schemes under different traffic patterns. Moreover, a prototype router based on the DyAD idea has been designed and evaluated. Compared to purely adaptive routers, the overhead of implementing DyAD is negligible (less than 7%), while the performance is consistently better.