The rapid emergence of Chip Multi-Processors (CMP) as the de facto microprocessor archetype has highlighted the importance of scalable and efficient on-chip networks. Packet-based Networks-on-Chip (NoC) are gradually cementing themselves as the medium of choice for the multi-/many-core systems of the near future, due to their innate scalability. However, the prominence of the debilitating power wall requires the NoC to also be as energy efficient as possible. To achieve these two antipodal requirements—scalability and energy efficiency—we propose TornadoNoC, an interconnect architecture that employs a novel flow control mechanism. To prevent livelocks and deadlocks, a sequence numbering scheme and a dynamic ring inflation technique are proposed, and their correctness formally proven. The primary objective of TornadoNoC is to achieve substantial gains in (a)  scalability  to many-core systems and (b) the  area/power  footprint, as compared to current state-of-the-art router implementations. The new router is demonstrated to provide better scalability to hundreds of cores than an ideal single-cycle wormhole implementation and other scalability-enhanced low-cost routers. Extensive simulations using both synthetic traffic patterns and real applications running in a full-system simulator corroborate the efficacy of the proposed design. Finally, hardware synthesis analysis using commercial 65nm standard-cell libraries indicates that the area and power budgets of the new router are reduced by up to 53p and 58p, respectively, as compared to existing state-of-the-art low-cost routers.
['Jung-Hee Lee', 'Chrysostomos Nicopoulos', 'Hyung Gyu Lee', 'Jongman Kim']
TornadoNoC: A lightweight and scalable on-chip network architecture for the many-core era