TooT: an efficient and scalable power-gating method for NoC routers

Abstract

With the advent in technology and shrinking the transistor size down to nano scale, static power may become the dominant power component in Networks-on-Chip (NoCs). Powergating is an efficient technique to reduce the static power of under-utilized resources in different types of circuits. For NoC, routers are promising candidates for power gating, since they present high idle time. However, routers in a NoC are not usually idle for long consecutive cycles due to distribution of resources in NoC and its communication-based nature, even in low network utilizations. Therefore, power-gating loses its efficiency due to performance and power overhead of the packets that encounter powered-off routers. In this paper, we propose Turn-on on Turn (TooT) which reduces the number of wake-ups by leveraging the characteristics of deterministic routing algorithms and mesh topology. In the proposed method, we avoid powering a router on when it forwards a straight packet or ejects a packet, i.e., a router is powered on only when either a packet turns through it or its associated node injects a packet. Experimental results on PARSEC benchmarks demonstrate that, compared with the conventional power-gating, the proposed method improves static power and performance by 57.9% and 35.3%, respectively, at the cost of a negligible area overhead.