Dataflow: A Complement to Superscalar

There has been a resurgence of interest in dataflow architectures, because of their potential for exploiting parallelism with low overhead. In this paper we analyze the performance of a class of static dataflow machines on integer media and control-intensive programs and we explain why a dataflow machine, even with unlimited resources, does not always outperform a superscalar processor on general-purpose codes, under the assumption that both machines take the same time to execute basic operations. We compare a program-specific dataflow machine with unlimited parallelism to a superscalar processor running the same program. While the dataflow machines provide very good performance on most data-parallel programs, we show that the dataflow machine cannot always take advantage of the available parallelism. Using the dynamic critical path we investigate the mechanisms used by superscalar processors to provide a performance advantage and their impact on a dataflow model.