A formally verified deadlock-free routing function in a fault-tolerant NoC architecture

Abstract

A novel fault-tolerant adaptive wormhole routing function for Networks-on-Chips (NoCs) is presented. The routing function guarantees absence of deadlocks and livelocks up to two faulty channels. The routing logic does not require reconfiguration when a fault occurs. The routes themselves are dynamic. Based on the faults in the network, alternative routes are used to reroute packets. Routing decisions are based only on local knowledge, which allows for fast switching. Our approach does not use any costly virtual channels. As we do not prohibit cyclic dependencies, the routing function provides minimal routing from source to destination even in the presence of faults. We have implemented the architecture design using synthesizable HDL. To ensure deadlock freedom, we have extended a formally verified deadlock detection algorithm to deal with fault tolerant designs. For a 20×20 mesh, we have formally proven deadlock freedom of our design in all of the 2,878,800 configurations in which two channels are faulty. We supply experimental results showing the performance of our architecture.