A Low-Power Branch Predictor for Embedded Processors

Sung Woo CHUNG  Gi Ho PARK  Sung Bae PARK  

IEICE TRANSACTIONS on Information and Systems   Vol.E87-D   No.9   pp.2253-2257
Publication Date: 2004/09/01
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: LETTER
Category: Computer Systems
microarchitecture,  branch predictor,  global predictor,  gshare,  low-power design,  

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Even in embedded processors, the accuracy in a branch prediction significantly affects the performance. In designing a branch predictor, in addition to accuracy, microarchitects should consider area, delay and power consumption. We propose two techniques to reduce the power consumption; these techniques do not requires any additional storage arrays, do not incur additional delay (except just one MUX delay) and never deteriorate accuracy. One is to look up two predictions at a time by increasing the width (decreasing the depth) of the PHT (Prediction History Table). The other is to reduce unnecessary accesses to the BTB (Branch Target Buffer) by accessing the PHT in advance. Analysis results with Samsung Memory Compiler show that the proposed techniques reduce the power consumption of the branch predictor by 15-52%.