Computer performance scaling is critical to advances in a wide range of fields, including medicine, telecommunications, climate science, weather forecasting, engineering, and design. With the rise of multicore systems and increasing processor-core count as the hardware mechanism for increased compute power, parallel program performance is now critical to continue this performance scaling. This work emphasizes latency reduction as this will be the most important performance impediment as the number of processors increases. Electrical interconnections can support the large information bandwidth over small distance, for example, between neighboring processors. Packet switching can share bandwidth between processors at a cost of latency that increases with inter-processor spacing. This research involves the use of nano scale optics to implement an optical broadcast network that can address all processors during a single clock cycle. Media access control will partition information between the high bandwidth point to point messages to be packet switched and latency bound synchronization messages to be optically broadcast. The investigators address the problem of a hybrid on-chip interconnection network both experimentally and theoretically. The bulk of the experimental work will involve fabricating and demonstrating the operation of nanophotonic broadcast network. The broadcast network will consist of a two dimensional slab waveguide region addressed with optical antennas that are fed and read out from nanophonic channel waveguide components. Optical sources will be placed off-chip and input to the netwrk through silicon on insulator waveguides. Wavelength division multiplexing will provide multi simultaneous channel operation through the single transceiver per processor interconnect. The media access control that partitions inter processor communication into high bandwidth packet switched communications and latency bound synchronization messages will be simulated using experimental data and phenomenological models of the actual interconnection network.
