Network-on-Chip design and synthesis outlook

With the growing complexity in consumer embedded products, new tendencies forecast heterogeneous Multi-Processor Systems-On-Chip (MPSoCs) consisting of complex integrated components communicating with each other at very high-speed rates. Intercommunication requirements of MPSoCs made of hundreds of cores will not be feasible using a single shared bus or a hierarchy of buses due to their poor scalability with system size, their shared bandwidth between all the attached cores and the energy efficiency requirements of final products. To overcome these problems of scalability and complexity, Networks-On-Chip (NoCs) have been proposed as a promising replacement to eliminate many of the overheads of buses and MPSoCs connected by means of general-purpose communication architectures. However, the development of application-specific NoCs for MPSoCs is a complex engineering process that involves the definition of suitable protocols and topologies of switches, and which demands adequate design flows to minimize design time and effort. In fact, the development of suitable high-level design and synthesis tools for NoC-based interconnects is a key element to benefit from NoC-based interconnect design in nanometer-scale CMOS technologies. In this article we overview the benefits of state-of-the-art NoCs using a complete NoC synthesis flow, and a detailed scalability analysis of different NoC implementations for the latest nanometer-scale technology nodes. We present NoC-based solutions for the on-chip interconnects of MPSoCs that illustrate the benefits of competitive application-specific NoCs with respect to more regular NoC topologies regarding performance, area and power. Moreover, we show that it is currently feasible to synthesize in an automatic way a complete custom NoC interconnect from a high-level specification in few hours. Finally, we summarize future research challenges in the area of NoC interconnect design automation.