OWN: Optical and Wireless Network-on-Chip for Kilo-core Architectures

Abstract

As technology scaling is already enabling the integration of tens of hundreds of cores on a single chip, kilo-core chip multiprocessors (CMPs) are expected to be available within a decade. However, metallic-based on-chip interconnects may not scale to support kilo-core architectures due to increased hop count, high power dissipation, and increased latency. Emerging technologies such as silicon-photonics and wireless interconnects are under serious consideration as they show promising results for power-efficient, low-latency, and scalable on-chip interconnects. However, photonic technology suffers from scalability issues due to high component cost and complex arbitration while wireless technology lacks sufficient bandwidth for on-chip communication. In this paper, we propose an architecture called Optical-Wireless Network-on-Chip (OWN) that leverages the advantages of wireless and photonic technologies while circumventing the disadvantages of these two emerging technologies. Kilo-core OWN is designed such that one-hop photonic interconnect is used up to 64 cores (called a cluster). For communication beyond a cluster, one-hop wireless interconnect is proposed to enhance scalability. Both wireless and photonic bandwidths are efficiently shared using time division multiplexing (TDM). Moreover, packets routed across technologies are guaranteed to be deadlock-free. Our area results indicate that OWN requires 34% more area than hybrid-wireless architectures and 35.5% less area than photonic architectures. The energy/bit for OWN is 30.36% less than wireless and 13.99% more than photonic architecture. OWN demonstrates higher saturation throughput when compared to wired, wireless, and photonic technologies for synthetic network traffic.