Tree-Mesh Heterogeneous Topology for Low-Latency NoC

Abstract

In Network-on-Chip (NoC), topology is one of the most important design choices that determine performance and power consumption. Mesh, being the most popular NoC topology for many researches and products, is mainly tailored towards high throughput. However, many researches show that NoCs rarely operate under heavy load and that latency is often much more critical in practice. In this paper, I show that by adding a small tree network to assist the baseline mesh network, the zero-load latency can be greatly reduced while still maintaining the high throughput. For the management of the hybrid network, I propose a novel algorithm to steer each packet to different networks based on hop-count gain. The algorithm also includes latency monitoring scheme and contention monitoring scheme in order to prevent tree network to get contested too much. Experiments were performed not only on synthetic traffics but also on real application workloads to evaluate the performance of the proposed design. The results show improvements on zero-load latency, throughput, and moreover, energy consumption.