Pipeline gating

Abstract

Branch prediction has enabled microprocessors to increase instruction level parallelism (ILP) by allowing programs to speculatively execute beyond control boundaries. Although speculative execution is essential for increasing the instructions per cycle ([PC). it does come at a cost. A large amount of unnecessaq work results from wrong-path instructions entering the pipeline due to branch misprediction. Results generated with the SimpleScalar tool set using a 4-way issue pipeline and various branch predictors show an instruction overhead of 16% to 105% for even' instruction committed. The instruction overhead will increase in. the future as processors use more aggressive speculation and wider issue widths [9].