Multistage Function Speculation Adders

Yinan SUN  Yongpan LIU  Zhibo WANG  Huazhong YANG  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E98-A   No.4   pp.954-965
Publication Date: 2015/04/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E98.A.954
Type of Manuscript: PAPER
Category: VLSI Design Technology and CAD
multistage function speculation,  variable latency adder,  design methodology,  

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Function speculation design with error recovery mechanisms is quite promising due to its high performance and low area overhead. Previous work has focused on two-stage function speculation and thus lacks a systematic way to address the challenge of the multistage function speculation approach. This paper proposes a multistage function speculation with adaptive predictors and applies it in a novel adder. We deduced the analytical performance and area models for the design and validated them in our experiments. Based on those models, a general methodology is presented to guide design optimization. Both analytical proofs and experimental results on the fabricated chips show that the proposed adder's delay and area have a logarithmic and linear relationship with its bit number, respectively. Compared with the DesignWare IP, the proposed adder provides the same performance with 6-17% area reduction under different bit lengths.