ASSESSING TRENDS IN THE ELECTRICAL EFFICIENCY OF COMPUTATION OVER TIME Jonathan G. Koomey*, Stephen Berard†, Marla Sanchez††, Henry Wong** * Lawrence Berkeley National Laboratory and Stanford University †Microsoft Corporation ††Lawrence Berkeley National Laboratory **Intel Corporation Contact:
[email protected], http://www.koomey.com Final report to Microsoft Corporation and Intel Corporation Submitted to IEEE Annals of the History of Computing: August 5, 2009 Released on the web: August 17, 2009 EXECUTIVE SUMMARY Information technology (IT) has captured the popular imagination, in part because of the tangible benefits IT brings, but also because the underlying technological trends proceed at easily measurable, remarkably predictable, and unusually rapid rates. The number of transistors on a chip has doubled more or less every two years for decades, a trend that is popularly (but often imprecisely) encapsulated as “Moore’s law”. This article explores the relationship between the performance of computers and the electricity needed to deliver that performance. As shown in Figure ES-1, computations per kWh grew about as fast as performance for desktop computers starting in 1981, doubling every 1.5 years, a pace of change in computational efficiency comparable to that from 1946 to the present. Computations per kWh grew even more rapidly during the vacuum tube computing era and during the transition from tubes to transistors but more slowly during the era of discrete transistors. As expected, the transition from tubes to transistors shows a large jump in computations per kWh. In 1985, the physicist Richard Feynman identified a factor of one hundred billion (1011) possible theoretical improvement in the electricity used per computation.