XYZ-Randomization using TSVs for low-latency energy efficient 3D-NoCs

In this paper, we propose a method to design low latency and low energy networks for 3D Network-on-Chip (3D-NoC). Recent many-core processors require low-latency interconnection networks since the increasing number of cores limits the network performance. To achieve high performance in such many-core chips, small-world or random networks have been applied in the NoC field. However, the actual diameters and average shortest path lengths (ASPL) of these networks are far from the theoretical lower bound. In this work, we propose an approach based on the graph theory to design ultra low-latency topologies. We introduce a method to design a network that has low values of diameter and ASPL, with configurable upper bound of wire length, called opt ASPL. We also show that irregular topology, such as the topology used in opt ASPL, has a higher average energy consumption than general regular topology like 3D torus. In NoCs, energy budget and link length are limited, and thus such parameters must be carefully considered. Therefore, we introduce a multi-objective optimization for the ASPL and energy consumption called opt A/e which can obtain the Pareto optimal set useful for NoC designers. In a router with 64 nodes per chips and 4 chips stacked with a 3D-NoC, our proposed network optimized for energy consumption has a lower ASPL by 26.8% and a lower energy consumption by 10.9% compared to a 3D torus.