Switch folding: Network-on-Chip routers with time-multiplexed output ports

On-chip interconnection networks simplify the increasingly challenging process of integrating multiple functional modules in modern Systems-on-Chip (SoCs). The routers are the heart and backbone of such networks, and their implementation cost (area/power) determines the cost of the whole network. In this paper, we explore the time-multiplexing of a router´s output ports via a folded datapath and control, where only a portion of the router´s arbiters and crossbar multiplexers are implemented, as a means to reduce the cost of the router without sacrificing performance. In parallel, we propose the incorporation of the switch-folded routers into a new form of heterogeneous network topologies, comprising both folded (time-multiplexed) and unfolded (conventional) routers, which leads to effectively the same network performance, but at lower area/energy, as compared to topologies composed entirely of full-fledged wormhole or virtual-channel-based router designs.