Adaptive Bubble Router: A Design to Improve Performance in Torus Networks

International Conference on Parallel Processing


A router design for torus networks that significantly re- duces message latency over traditional wormhole routers is presented in this paper. This new router implements virtual cut-through switching and fully-adaptive minimal routing. Packet deadlock is avoided by providing escape ways gov- erned by Bubble flow control, a mechanism that guarantees enough free buffer space in the network to allow continuous packet movement. Both deterministic and adaptive Bubble routers have been designed in VLSI using VHDL synthesis tools. Adopt- ing a fair quantitative comparison, we demonstrate that Bubble routers exhibit a reduction in base latency val- ues over 40% with respect to the corresponding wormhole routers, without any penalty in network throughput. With much lower VLSI costs than adaptive wormhole routers, the adaptive Bubble router is even faster than determinis- tic wormhole routers based on virtual channels.