Partially Adaptive Look-Ahead Routing for Low Latency Network-on-Chip

Adaptive routing algorithms offer the ability to avoid congestion by supporting multiple paths between a source and destination. However, supporting adaptive routing for low latency routers is a challenge due to the computation of routing algorithm in one router in advanced (i.e. look-ahead routing). This paper presents an RTL architecture of partially adaptive look-ahead routing algorithm on a recently proposed low latency, virtual channel wormhole Network-on-Chip (NoC) router. In our proposed design, each router pre-computes the preferred output ports based on its local congestion and transfers the preferred output ports to the neighbouring routers. These preferred output ports are used in the look-ahead routing to select the optimal output port for the packet. We compare our proposed partially adaptive routing architecture with the reference design using look-ahead XY routing algorithm under matrix-transpose traffic and obtained 10% improvement at maximum injection rate. Our proposed routing algorithm has negligible area overhead (<2%) while has no influence on maximum operating frequency.