Lightweight Message Encoding of Power-Gating Controller for On-Time Wakeup of Gated Router in Network-on-Chip

Power-gating has become one of the most widely used circuit design techniques to mitigate static power. Routers are the major contributor in Networks-on-Chip (NoC) power. The high idle time of practical applications can be utilised to power-off (gated) router in NoC. However, network performance is being compromised as the gated router disconnects the associated node from the rest of the network. Packets in the network face a router wakeup latency before reaching to their destinations. In this paper, we propose a Leon, Lightweight message encoding scheme for power-gating controller to wakeup the sleeping router at right-time on arrival of the packet. We maximize power-gating time of router by wakeup them not early than the required to a packet to maximize static power gains. Simultaneously, the packet does not face wakeup latency of the router as the prior sending of wakeup messages through dedicated signal lines activate router at exactly right-time when it is required. Thus, our proposed message encoding achieves a performance-aware maximal static power reduction wherein control signals stay ahead of packets and preventing packets from having to suffer router wakeup latency. Our experiments show that Leon reduces 39% network latency as compared to conventional power-gating. It enables total static power savings up to 89% on low traffic with a minor overhead in area and power over conventional power-gating. Also, hardware implementation benefits are 83% in area and 70% in power over state-of-the-art encoding.