Ch1_Introduction

Ch1_Introduction - Low Power Design Essentials ©2008 Jan...

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Unformatted text preview: Low Power Design Essentials ©2008 Jan M. Rabaey Low Power Design Essentials ©2008 Chapter 1 Introduction Low Power Design Essentials ©2008 Why Worry about Power? § Total Energy of Milky Way Galaxy: 1059 J § Minimum switching energy for digital gate (1 [email protected] mV): 1.6 10-20 J (limited by thermal noise) § Upper bound on number of digital operations: 6 1078 § Operations/year performed by 1 billion 100 MOPS computers: 3 1024 § Energy consumed in 180 years , assuming a doubling of computational requirements every year (Moore’s Law). The Tongue-in-Cheek Answer Low Power Design Essentials ©2008 Power the Dominant Design Constraint (1) Cost of large data centers solely determined by power bill … Google Data Center, The Dalles, Oregon Columbia River 8,000 100,000 450,000 NY Times, June 06 § 400 Millions of Personal Computers worldwide (Year 2000)- Assumed to consume 0.16 Tera (1012) kWh per year- Equivalent to 26 nuclear power plants § Over 1 Giga kWh per year just for cooling- Including manufacturing electricity [Ref: Bar-Cohen et al., 2000] Low Power Design Essentials ©2008 Power the Dominant Design Constraint [Ref: R. Schmidt, ACEED’03] Low Power Design Essentials ©2008 Chip Architecture and Power Density [Ref: R. Yung, ESSCIRC’02] Integration of diverse functionality on SoC causes major variations in activity (and hence power density) The past: temperature uniformity Today: steep gradients Temperature variations cause performance degradation – higher temperature means slower clock speed Low Power Design Essentials ©2008 Temperature Gradients (and Performance) IBM Power PC 4 temperature map [ Ref: R. Schmidt, ACEED’03] Hot spot: 138 W/cm2 (3.6 x chip avg flux) Glass ceramic substrate SiC spreader (chip underneath spreader) Copper hat (heat sink on top not shown) Low Power Design Essentials ©2008 Power the Dominant Design Constraint (2) Mobile Functionality Limited by Energy Budget [Ref: Y. Nuevo, ISSCC’04 ] Size of mobile sets energy supply Power consumption and Battery Capacity Trends © IEEE 2004 Low Power Design Essentials ©2008 Mobile Functionality Limited by Energy Budget [Ref: F. Snijders, Ambient Intelligence’05] Energy hierarchy in “ambient intelligent” environment © Springer 2005 Low Power Design Essentials ©2008 Battery Storage a Limiting Factor § Basic technology has evolved little – store energy using a chemical reaction § Battery capacity increases between 3% and 7 % per year (doubled during the 90’s, relatively flat before that) § Energy density/size, safe handling are limiting factor Energy density of material kWh/kg Gasoline 14 Lead-Acid 0.04 Li polymer 0.15 For extensive information on energy density of various materials, check http://en.wikipedia.org/wiki/Energy_density Low Power Design Essentials ©2008 1....
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This note was uploaded on 03/13/2010 for the course CSE 241a taught by Professor Chau,p during the Spring '08 term at UCSD.

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Ch1_Introduction - Low Power Design Essentials ©2008 Jan...

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