Strategies for Achieving Improved Processor Throughput

Deeply pipelined processors have relatively low issue rates due to dependencies between instructions. In this paper we examine the possibility of interleaving a second stream of instructions into the pipeline, which would issue instructions during the cycles the first stream was unable to. Such an interleaving has the potential to significantly increase the throughput of a processor without seriously imparing the execution of either process. We propose a dynamic interleaving of at most 2 instructions streams, which share the the pipelined functional units of a machine. To support the interleaving of 2 instruction streams a number of interleaving policies are described and discused. Finally, the amount of improvement in processor throughput is evaluated by simulating the interleaving policies for several machine variants. 1. Introduction An important metric for evaluating processor performance, especially in a multiprocessing context, is the throughput rate of a processor (defined as h..