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IBM Journal of Research and Development  
Volume 44, Number 1/2, Page 261 (2000)
Evolution of information technology 1957-1999
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Irreversibility and heat generation in the computing process

by R. Landauer
Please note: This previously published IBM Journal of Research and Development paper was reprinted for this special retrospective issue.

It is argued that computing machines inevitably involve devices which perform logical functions that do not have a single-valued inverse. This logical irreversibility is associated with physical irreversibility and requires a minimal heat generation, per machine cycle, typically of the order of kT for each irreversible function. This dissipation serves the purpose of standardizing signals and making them independent of their exact logical history. Two simple, but representative, models of bistable devices are subjected to a more detailed analysis of switching kinetics to yield the relationship between speed and energy dissipation, and to estimate the effects of errors induced by thermal fluctuations.

Related Subjects: Computers