Next Entries Pre-activation for Low Power Drowsy BTB

Abstract

Recently, low-power design becomes popular research topics. This paper addresses power mode management for drowsy BTB. We propose an accurate next entry pre-activation method cooperated with the decay policy to reduce BTB leakage energy consumption. In the decay policy, a BTB entry which has not been accessed for a period of time is put into drowsy mode. Moreover, the BTB locations of all branch instructions existing in BTB are cached for next BTB entry pre-activation. Simulation results show that our method reduces the leakage consumption in BTB by an average of 61.9% with only paying 0.5% performance cost.