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Research Papers

# From Chip to Cooling Tower Data Center Modeling: Chip Leakage Power and Its Impact on Cooling Infrastructure Energy Efficiency

[+] Author and Article Information
Thomas J. Breen

e-mail: thomas.breen@ul.ie

Jeff Punch

Stokes Institute,
University of Limerick,
Limerick, Ireland

Niru Kumari

Hewlett-Packard Laboratories,
Palo Alto, CA 94304

Liberty Lake, WA 99019

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the Journal of Electronic Packaging. Manuscript received June 5, 2012; final manuscript received August 27, 2012; published online November 26, 2012. Assoc. Editor: Siddharth Bhopte.

J. Electron. Packag 134(4), 041009 (Nov 26, 2012) (8 pages) doi:10.1115/1.4007744 History: Received June 05, 2012; Revised August 27, 2012

## Abstract

The power consumption of the chip package is known to vary with operating temperature, independently of the workload processing power. This variation is commonly known as chip leakage power, typically accounting for $~$10% of total chip power consumption. The influence of operating temperature on leakage power consumption is a major concern for the information technology (IT) industry for design optimization where IT system power densities are steadily increasing and leakage power expected to account for up to $~$50% of chip power in the near future associated with the reducing package size. Much attention has been placed on developing models of the chip leakage power as a function of package temperature, ranging from simple linear models to complex super-linear models. This knowledge is crucial for IT system designers to improve chip level energy efficiency and minimize heat dissipation. However, this work has been focused on the component level with little thought given to the impact of chip leakage power on entire data center efficiency. Studies on data center power consumption quote IT system heat dissipation as a constant value without accounting for the variance of chip power with operating temperature due to leakage power. Previous modeling techniques have also omitted this temperature dependent relationship. In this paper, we discuss the need for chip leakage power to be included in the analysis of holistic data center performance. A chip leakage power model is defined and its implementation into an existing multiscale data center energy model is discussed. Parametric studies are conducted over a range of system and environment operating conditions to evaluate the impact of varying degrees of chip leakage power. Possible strategies for mitigating the impact of leakage power are also illustrated in this study. This work illustrates that when including chip leakage power in the data center model, a compromise exists between increasing operating temperatures to improve cooling infrastructure efficiency and the increase in heat load at higher operating temperatures due to leakage power.

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## Figures

Fig. 1

Schematic of the data center cooling infrastructure

Fig. 2

Breakdown of chip power dissipation to processing power and leakage power illustrating the leakage gradient

Fig. 3

Data center IT power usage for fixed heat sink temperatures with THS,Leak0 = 20 °C and increasing leakage gradient. (a) THS50 °C, LX0.0W/°C. (b) THS50 °C, increasing LX. (c) Full range of THS and LX.

Fig. 4

Data center cooling infrastructure power usage for fixed heat sink temperatures (color coded) with THS,Leak0 = 20 °C and increasing leakage gradient

Fig. 5

Total data center facility power usage for fixed heat sink temperatures (color coded) with THS,Leak0 = 20 °C and increasing leakage gradient

Fig. 6

Breakdown of total data center facility power at 20 °C rack inlet temperature. (a) THS50 °C, LX0.0W/°C. (b) THS50 °C, LX1.0W/°C. (c) THS70 °C, LX0.0W/°C. (d) THS70 °C, LX1.0W/°C.

Fig. 7

Impact of the range of operating conditions on COP* for fixed heat sink temperatures (color coded) with THS,Leak0 = 20 °C and increasing leakage gradient

Fig. 8

Peak COP* for each LX across THS range for fixed heat sink temperatures with THS,Leak0 = 20 °C

Fig. 9

COP* values for linearly variable heat sink temperature with inlet air. THS,Leak0 = 20 °C and THSRef of 50 °C at 20 °C inlet air

Fig. 10

COP* values for linearly variable heat sink temperature with inlet air. THS,Leak0 = 20 °C and THSRef of 50 °C at 20 °C inlet air

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