Enhancing Network-on-Chip Performance by Reusing Trace Buffers

Abstract

Ensuring the functional correctness of networks-on-chip (NoCs) can be particularly challenging, and communication-centric debug methodologies have been widely used by engineers to validate NoC functionality during post-silicon validation. Design-for-debug structures, such as trace buffers and monitors, are usually inserted in such systems-on-chip to enhance signal visibility. However, this debug hardware becomes underutilized once the chip goes into production. While the size and organization of the router buffers directly impact network throughput, these buffers also dominate the on-chip router area. We propose a scheme augmented virtual channel (AugVC) to reuse trace buffers to augment router buffers, with the objective of improving the overall network performance. The experimental results for a 64-node mesh network show that our proposed approach can reduce latency by up to 38.25% for transpose traffic compared to a baseline design with reduced buffer sizes. We also propose an extension, output port directed virtual channel (ODVC), that uses a modified virtual channel assignment strategy, on the basis of the designated output port of a network packet. This strategy reduces the average packet latency and area of the router by 45% and 32.4%, respectively.