Dodec: Random-Link, Low-Radix On-Chip Networks

Network topology plays a vital role in chip design; it largely determines network cost (power and area) and significantly impacts communication performance in many-core architectures. Conventional topologies such as a 2D mesh have drawbacks including high diameter as the network scales and poor load balancing for the center nodes. We propose a methodology to design random topologies for on-chip networks. Random topologies provide better scalability in terms of network diameter and provide inherent load balancing. As a proof-of-concept for random on-chip topologies, we explore a novel set of networks - dodecs - and illustrate how they reduce network diameter with randomized low-radix router connections. While a 4 x 4 mesh has a diameter of 6, our dodec has a diameter of 4 with lower cost. By introducing randomness, dodec networks exhibit more uniform message latency. By using low-radix routers, dodec networks simplify the router microarchitecture and attain 20% area and 22% power reduction compared to mesh routers while delivering the same overall application performance for PARSEC.