Virtual Channels and Multiple Physical Networks: Two Alternatives to Improve NoC Performance

Virtual channels (VC) and multiple physical (MP) networks are two alternative methods to provide better performance, support quality-of-service, and avoid protocol deadlocks in packet-switched network-on-chip design. Since contention can be dynamically resolved, VCs give lower zero-load packet latency than MPs; however, MPs can be built with simpler routers and narrower channels, which improves the target clock frequency, power dissipation, and area occupation. In this paper, we present a comprehensive comparative analysis of these two design approaches, including an analytical model, synthesis-based designs with both FPGAs and standard-cell libraries, and system-level simulations. The result of our analysis shows that one solution does not outperform the other in all the tested scenarios. Instead, each approach has its own specific strengths and weaknesses. Hence, we identify the scenarios where each method is best suited to achieve high performance, very low power dissipation, and increased design flexibility.