Power punch: Towards non-blocking power-gating of NoC routers

As chip designs penetrate further into the dark silicon era, innovative techniques are much needed to power off idle or under-utilized system components while having minimal impact on performance. On-chip network routers are potentially good targets for power-gating, but packets in the network can be significantly delayed as their paths may be blocked by powered-off routers. In this paper, we propose Power Punch, a novel performance-aware, power reduction scheme that aims to achieve non-blocking power-gating of on-chip network routers. Two mechanisms are proposed that not only allow power control signals to utilize existing slack at source nodes to wake up powered-off routers along the first few hops before packets are injected, but also allow these signals to utilize hop count slack by staying ahead of packets to "punch through " any blocked routers along the imminent path of packets, preventing packets from having to suffer router wakeup latency or packet detour latency. Full system evaluation on PARSEC benchmarks shows Power Punch saves more than 83% of router static energy while having an execution time penalty of less than 0.4%, effectively achieving near non-blocking power-gating of on-chip network routers.