Synthesis of low-overhead configurable source routing tables for network interfaces

In on-chip multiprocessor communication, link failures and dynamically changing application scenarios represent demanding constraints for the provision of suitable Quality of Service. Networks-on-Chip (NoCs) featuring dynamic routing are a known way to tackle these issues, but deadlock freedom and message ordering concerns arise. NoCs with configurable routing, whereby the communication routes are explicitly chosen at runtime out of a set of statically predefined alternatives, provide intelligent adaptation without impacting the consistency of traffic flows. However, configurable source routing on a NoC platform requires a design that provides fast path lookup coupled with low area and power consumption. This paper presents an exploration and synthesis approach that, depending on the required amount of routing flexibility, can for example reduce by 3 to 15 times the area cost of the NoC routing tables by adopting partially reprogrammable routing logic instead of fully reprogrammable tables. Further optimizations based on path redundancy allow to reduce up to 17 times the silicon cost.