Proceedings of the 40th Annual International Symposium on Computer Architecture - ISCA '13
Multiple networks have been used in several processor implementations to scale bandwidth and ensure protocol-level deadlock freedom for different message classes. In this paper, we observe that a multiple-network design is also attractive from a power perspective and can be leveraged to achieve energy proportionality by effective power gating. Unlike a single-network design, a multiple-network design is more amenable to power gating, as its subnetworks (subnets) can be power gated without
... gated without compromising the connectivity of the network. To exploit this opportunity, we propose the Catnap architecture which consists of synergistic subnet selection and powergating policies. Catnap maximizes the number of consecutive idle cycles in a router, while avoiding performance loss due to overloading a subnet. We evaluate a 256-core processor with a concentrated mesh topology using synthetic traffic and 35 applications. We show that the average network power of a power-gating optimized multiplenetwork design with four subnets could be 44% lower than a bandwidth equivalent single-network design for an average performance cost of about 5%.