On Chip Network Routing for Tera-Scale Architectures

The emergence of Tera-scale architectures features the interconnection of tens to several hundred general purpose cores to each other and with other IP blocks. The high level requirements of the underlying interconnect infrastructure include low latency, high-throughput, scalable performance, flexible and adaptive routing, support for isolated partitions, fault-tolerance, and support for irregular or partially enabled configurations. This chapter presents the architecture and routing algorithms for supporting these requirements in the overall framework of mesh and torus-based point-to-point interconnect topologies. The requirements and desired attributes for tera-scale interconnects are outlined. This is followed by an overview of the interconnect architecture and micro-architecture framework. The descriptions of various routing algorithms supported are at the heart of the chapter, and include various minimal deterministic and adaptive routing algorithms for mesh and torus networks, a novel load-balanced routing algorithm called pole-routing, and performance-isolation routing in non-rectangular mesh partitions. The implementation aspects of these topics is covered through an overview of the environment for prototyping, debugging, performance evaluation and visualization in the context of specific interconnect configurations of interest. Overall, this chapter aims to illustrate a comprehensive approach in architecting (and micro-architecting) a scalable and flexible on-die interconnect and associated routing algorithms that are applicable to a wide range of applications in an industry setting.