LastZ: An Ultra Optimized 3D Networks-on-Chip Architecture

3D IC technology enables NoC architectures to offer greater device integration and shorter interlayer interconnects. The primary 3D NoC architectures such as Symmetric 3D Mesh NoC could not exploit the beneficial feature of a negligible inter-layer distance in 3D chips. To cope with this, 3D NoC-Bus Hybrid architecture was proposed which is a hybrid between packet-switched network and a bus. This architecture is feasible providing both performance and area benefits, while still suffering from naive and straightforward hybridization between NoC and bus media. In this paper, an ultra optimized hybridization scheme is proposed to enhance system performance, power consumption, area and thermal issues of 3D NoC-Bus Hybrid Mesh. The scheme benefits from a rule called \emph{LastZ} which enables ultra optimization of the inter-layer communication architecture. In addition, we present a wrapper to preserve the backward compatibility of the proposed architecture for connecting with the existing network interfaces. To estimate the efficiency of the proposed architecture, the system has been simulated using uniform, hotspot 10\%, and Negative Exponential Distribution (NED) traffic patterns. Our extensive simulations demonstrate significant area, power, and performance improvements compared to a typical 3D NoC-Bus Hybrid Mesh architecture.