Fine-Grained Run-Tume Power Gating through Co-optimization of Circuit, Architecture, and System Software Design

Hiroshi NAKAMURA  Weihan WANG  Yuya OHTA  Kimiyoshi USAMI  Hideharu AMANO  Masaaki KONDO  Mitaro NAMIKI  

IEICE TRANSACTIONS on Electronics   Vol.E96-C    No.4    pp.404-412
Publication Date: 2013/04/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E96.C.404
Print ISSN: 0916-8516
Type of Manuscript: Special Section INVITED PAPER (Special Section on Solid-State Circuit Design—Architecture, Circuit, Device and Design Methodology)
low-power circuit techniques,  fine grained power-gating,  compiler,  system hierarchy cooperation,  

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Power consumption has recently emerged as a first class design constraint in system LSI designs. Specially, leakage power has occupied a large part of the total power consumption. Therefore, reduction of leakage power is indispensable for efficient design of high-performance system LSIs. Since 2006, we have carried out a research project called “Innovative Power Control for Ultra Low-Power and High-Performance System LSIs”, supported by Japan Science and Technology Agency as a CREST research program. One of the major objectives of this project is reducing the leakage power consumption of system LSIs by innovative power control through tight cooperation and co-optimization of circuit technology, architecture, and system software designs. In this project, we focused on power gating as a circuit technique for reducing leakage power. Temporal granularity is one of the most important issue in power gating. Thus, we have developed a series of Geysers as proof-of-concept CPUs which provide several mechanisms of fine-grained run-time power gating. In this paper, we describe their concept and design, and explain why co-optimization of different design layers are important. Then, three kinds of power gating implementations and their evaluation are presented from the view point of power saving and temporal granularity.