Cross-layer Energy and Performance Evaluation of a Nanophotonic Manycore Processor System Using Real Application Workloads

Recent advances in nanophotonic device research have led to a proliferation of proposals for new architectures that employ optics for on-chip communication. However, since standard simulation tools have not yet caught up with these advances, the quality and thoroughness of the evaluations of these architectures have varied widely. This paper provides the first complete end-to-end analysis of an architecture using on-chip optical interconnect. This analysis incorporates realistic performance and energy models for both electrical and optical devices and circuits into a full-fledged functional simulator, thus enabling detailed analyses when running actual applications. Since on-chip optics is not yet mature and unlikely to see widespread use for several more years, we perform our analysis on a future 1000-core processor implemented in an 11nm technology node. We find that the proposed optical interconnect can provide between 1.8x and 4.8x better energy-delay product than conventional electrical-only interconnects. In addition, based on a detailed energy breakdown of all processor components, we conclude that a thermal ring resonators and on-chip lasers that allow rapid power gating are key areas worthy of additional nanophotonic research. This will help guide future optical device research to the areas likely to provide the best payoff.