Sustainability in Network-on-Chips by Exploring Heterogeneity in Emerging Technologies

With the scaling of technology, the computing industry is experiencing a shift from multi-core to many-core architectures. However, traditional metallic-based on-chip interconnects may not scale to support many-core architectures due to high power dissipation, and increased communication latency. Attention has recently shifted to emerging technologies such as silicon-photonics and wireless interconnects to implement future on-chip communications. Although emerging technologies show promising results for power-efficient, low-latency, and scalable on-chip interconnects, the use of single technology may not be sufficient to scale future architectures. In this paper, we extend the heterogeneous architecture Optical-Wireless Network-on-Chip (OWN [1]) to Reconfigurable Optical-Wireless Network-on-Chip (R-OWN) by introducing run-time reconfigurable wireless channels. Like OWN, R-OWN is designed such that one-hop photonic interconnect is used up to 64 cores (called a cluster) and communication beyond a cluster is one-hop wireless to limit the network diameter to a maximum of three hops. The photonic bandwidth is efficiently shared using time division multiplexing (TDM) while the wireless bandwidth is shared using frequency division multiplexing (FDM). By exploiting the heterogeneity of two emerging technologies, we reduce the energy/bit, improve performance via reconfiguration, and thereby improve the sustainability of NoCs and CMPs. We propose a preliminary assessment of implementing heterogeneous technologies with the router microarchitecture. Further, we also discuss the design of horn antenna for implementing the wireless channels. Our results indicate that R-OWN improves the performance (throughput and latency) by 15 percent when compared to OWN while consuming 7 percent more energy than OWN. Further, OWN and R-OWN improve energy-efficiency by 54-61 percent when compared to WCube and CMesh architectures, respectively. It should be noted that both OWN and R-OWN require less area than state-of-the-art wired, wireless, and optical on-chip networks.