Exploring Topologies for Source-synchronous Ring-based Network-on-Chip

The mesh interconnection network has been preferred by the Network-on-Chip (NoC) community due to its simple implementation, high bandwidth and overall scalability. Most existing mesh-based NoC designs operate the mesh at the same or lower clock speed as the processing elements (PEs). Recently, a new source synchronous ring-based NoC architecture has been proposed, which runs significantly faster than the PEs and offers a significantly higher bandwidth and lower communication latency. The authors implement the NoC topology as a mesh of rings, which occupies the same area as that of a mesh. In this work, we evaluate two alternate source synchronous ring-based NoC topologies called the ring of stars (ROS) and the spine with rings (SWR), which occupy a much lower area, and are able to provide better performance in terms of communication latency compared to a state of the art mesh. In our proposed topologies, the clock and the data NoC are routed in parallel, yielding a fast, synchronous, robust design. Our design allows the PEs to extract a low jitter clock from the high speed ring clock by division. The area and performance of these ring-based NoC topologies is quantified. Experimental results on synthetic traffic show that the new ring-based NoC designs can provide significantly lower latency (upto 4.6x) compared to a state of the art mesh. The proposed floorplan-friendly topologies use fewer buffers (upto 50% less) and lower wire length (upto 64.3% lower) compared to the mesh. Depending on the performance and the area desired, a NoC designer can select among the topologies presented.