Performance modeling and code partitioning for the DS architecture

Abstract

DS (Decoupled-Superscalar) is a new microarchitecture that combines decoupled and superscalar techniques to exploit instruction level parallelism. Issue bandwidth is increased while circuit complexity growth is controlled with little negative impact on performance. Programs for DS are compiled into two instruction substreams: the dominant substream navigates the control flow and the rest of computational task is shared between the dominant and subsidiary substreams. Each substream is processed by a separate superscalar core realizable with current VLSI technology. DS machines are binary compatible with superscalar machines having the same instruction set, and a family of DS machines is binary compatible without recompilation. DS run time behavior is examined with an analytical model. A novel technique for controlling slip between substreams is introduced. Code partitioning issues of instruction count balancing and residence time balancing, important to any split-stream scheme, are discussed. Simulation shows DS achieves performance comparable to an aggressive superscalar, but with potentially less complex hardware and faster clock rate.