Energy-Efficient and Fault-Tolerant Unified Buffer and Bufferless Crossbar Architecture for NoCs

Network-on-Chip (NoC) architecture is considered to be an attractive solution to overcome the combined problems of limited bandwidth and scalability in multicores. Input buffering at the router allows the network to sustain the accepted throughput without performance degradation. However, the input buffers consume a substantial portion of the total power budget, and there have been proposals to reduce the size of these buffers. Eliminating buffers altogether can also reduce the power consumption at low network loads, however at higher loads when conflicts are frequent, deflecting or dropping packets can lead to higher power. In this paper, with both enhancing performance and decreasing power consumption as our goals, we propose a dual-input crossbar design called DXbar, which combines the advantages of bufferless networks to enable low-latency routing at low network load and limited buffering capability to handle excessive packets at high network load. Moreover, we also propose a unified dual-input crossbar that combines the bufferless and buffered approach in one integrated architecture. The dual crossbar network naturally provides fault tolerance and improves the reliability of the network. Dual-input crossbar architecture improves the area overhead, while providing similar performance as dual crossbar architecture. DXbar design not only has superior performance compared to the state-of-the-art designs based on similar motivation, but also achieves significant power savings. The simulation results of the proposed methodology show that DXbar achieves over 15-20% performance improvement and saves at least 15% power over the baseline design for synthetic and Splash-2 benchmarks. We further evaluated the performance by injecting varying percentage of faults into the network for both DOR and WF adaptive routing algorithms. Our results indicate that DOR outperforms WF adaptive routing algorithm at high network loads with increasing percentage of faults.