REDELF: An energy-efficient deadlock-free routing for 3D NoCs with Partial Vertical Connections

3D integrated circuits (3D ICs) using through-silicon vias (TSVs) allow to envision the stacking of dies with different functions and technologies, using as an interconnect backbone a 3D network-on-chip (NoC). However, partial vertical connection in 3D NoCs seems unavoidable because of the large overhead of TSV itself (e.g., large footprint, low fabrication yield, additional fabrication processes) as well as the heterogeneity in dimension. This article proposes an energy-efficient deadlock-free routing algorithm for 3D mesh topologies where vertical connections partially exist. By introducing some rules for selecting elevators (i.e., vertical links between dies), the routing algorithm can eliminate the dedicated virtual channel requirement. In this article, the rules themselves as well as the proof of deadlock freedom are given. By eliminating the virtual channels for deadlock avoidance, the proposed routing algorithm reduces the energy consumption by 38.9% compared to a conventional routing algorithm. When the virtual channel is used for reducing the head-of-line blocking, the proposed routing algorithm increases performance by up to 23.1% and 6.9% on average.