A Lightweight Early Arbitration Method for Low-Latency Asynchronous 2D-Mesh NoC's
Weiwei Jiang, Kshitij Bhardwaj, Geoffray Lacourba, Steven M. Nowick · 2015
A new asynchronous low-latency interconnection network is introduced for a 2D mesh topology. The network-on-chip, named AEoLiAN, contains a fast lightweight monitoring network to notify the routers of incoming traffic, thereby allowing arbitration and channel allocation to be initiated in advance. In contrast, several recent synchronous early arbitration methods require significant resource overhead, including use of hybrid networks, or wide monitoring channels and additional VCs. The proposed approach has much smaller overhead, allowing a finer-grain router-by-router early arbitration, with monitoring and data advancing independently at different speeds. The new router was implemented in 45nm technology using a standard cell library. It had 52% lower area than a similar lightweight synchronous switch, xpipesLite, with no early arbitration capability. Network-level simulations were then performed on 6 diverse synthetic benchmarks in an 8x8 2D mesh network topology, and the performance of the new network was compared to an asynchronous baseline. Considerable improvements in system latency over all benchmarks for moderate traffic were obtained, ranging from 34.4-37.9%. Interestingly, the proposed acceleration technique also enabled throughput gains, ranging from 14.7-27.1% for the top 5 benchmarks. In addition, a zero-load end-to-end latency of only 4.9ns was observed, for the longest network path through 15 routers and 14 hops.