Towards an Effective Utilization of Partially Defected Interconnections in 2D Mesh NoCs

In typical NoC systems, most Routing Algorithms (RAs) abandon the interconnection between two adjacent routers if one traffic direction is broken, despite whether the other one is still functional or not. In this paper, we propose a distributed logic based RA, which can efficiently utilize the UnPaired Functional (UPF) links in such partially defected interconnects. The basic fault pattern tolerated by the proposed RA is a fault wall, which is composed of adjacent broken links with the same outgoing direction. Messages are routed around the fault walls along the misrouting contours of the broken links. The proposed RA requires at least 3 Virtual Channels (VCs) and dynamically reserve them to misrouted messages to avoid deadlock. Our experiments indicate that, for random and localized traffic patterns, we achieve an average saturation throughput 20% higher than the Solid Fault Region Tolerant (SFRT) RA, and 22% and 14% higher than the Ariadne routing table based RA, respectively. For the real applications, sample and satell, our proposal requires a routing execution time with at least 16% shorter than both SFRT and Ariadne. Synthesis results with Synopsis Design Compiler and TSMC 65nm technology indicate that, embedding the proposed RA into a baseline router results in 11% area overhead, which is only 3% higher than that of SFRT. In contrast, Ariadne area overhead is 15% for an 8 × 8 NoC and increases to 21% for a 10 × 10 NoC.