HPPT-NoC: A Dark-Silicon Inspired Hierarchical TDM NoC with Efficient Power-Performance Trading

摘要

Networks-on-chip (NoCs) acquired substantial advancements as the typical solution for a modular, flexible and high performance communication infrastructure coping with the scalable Multi-/Manycores technology. However, the increasing chip complexity heading towards thousand cores, together with the approaching dark-silicon era, puts energy efficiency as an integral design key for future NoC-based multicores, where NoCs are significantly contributing to the total chip power. In this paper, we propose HPPT-NoC, a dark-silicon inspired energy-efficient hierarchical TDM NoC with online distributed setup-scheme. The proposed network makes use of the dim silicon parts of the chip to hierarchically connect quad-routers units. Normal routers operate at full-chip-frequency at high supply level, and hierarchical routers operate at half-chip-frequency and lower supply voltage with adequate synchronization. Routers follow a proposed TDM architecture that separates the datapath from the control-setup planes. This allows separate clocking and operating supplies between data and control and to keep the control-setup as a single-slot-cycle design independent of the datapath slot size. The proposed NoC architecture is evaluated versus a base NoC from the state-of-the-art in terms of performance and hardware results using Synopsys VCS and Synopsys Design Compiler for SAED90nm and SAED32nm technologies. The obtained results highlight the power-frequency-trading feature supported by the proposed hierarchical NoC through the configurable data-control clock relation and maintained over the different technology nodes. With the same power budget of the base NoC, the proposed architecture provides up to 74% setup latency enhancement, 32% increased NoC saturation load, and 21% higher success rates, offering up to 78% improved power delay product. On the other hand, with 38% power savings, the proposed NoC provides up to 37% enhanced latency and 15% higher success rates, with 72% enhanced power delay product. The proposed design consumes almost double the area of the base NoC, however with an average of 56% under-clocked (dim) silicon area operating at half to quarter the maximum chip frequency. This results in reduced power density as a main concern in the dark-silicon era down to 24% of the base NoC.