Comparison of the communication latency for an opticalbus and for several 2 D electronic network topologiesJ

We study the reduction of the internode communication latency in distributed-memory multiprocessor machines on the assumption of developing a new generation of optical busses. We consider quasi-transparent optical busses which convey optical packets in the asynchronous mode. The critical property of these busses is that the intranode latency is small compared to the internode propagation time so that the propagation of packets along the bus is determined by the sole velocity of light in the bers. For 2D networks, this is just the contrary: the electronic node processing time generally controls the propagation of messages. We show that the optical bus outdoes several 2D electronic topologies both for the shortness of the latency and for the magnitude of the bandwidth. We brieey summarize in the last section the physical implementation of the optical bus and the structure of the bus/node interface.