Optimizing a decoupled front-end architecture: The indexed fetch target buffer (iFTB)

Abstract

A decoupled front-end architecture relies on a separate fetch predictor that is critical in determining the fetch bandwidth. The Fetch Target Buffer (FTB) is a multilevel fetch predictor design. In this paper we propose and analyze a variation of the FTB, the indexed Fetch Target Buffer (iFTB), that uses an extra, very fast, index table to speedup its operations. The iFTB achieves very accurate predictions by adapting a complex hybrid branch predictor to suit its short cycle time. With a low hardware cost, the iFTB delivers instructions between 15% and 45% faster than the FTB. © Springer-Verlag 2003.