A Comparison of Dynamic Branch Predictors that use Two Levels of Branch History Tse

Recent attention to speculative execution as a mechanism for increasing performance of single instruction streams has demanded substantially better branch prediction than what has been previously available. We 1, 2] and Pan, So, and Rahmeh 4] have both proposed variations of the same aggressive dynamic branch pre-dictor for handling those needs. We call the basic model Two-Level Adaptive Branch Predictionn Pan, So, and Rahmeh call it Correlation Branch Prediction. In this paper, we adopt the terminology of 2] and show that there a r e r eally nine variations of the same basic model. We compare the nine variations with respect to the amount of history information kept. We study the eeects of diierent branch history lengths and pattern history table conngurations. Finally, we evaluate the cost eeectiveness of the nine variations.