Save energy, turn up the heat

The efficiency of a machine, whether it is a steam engine or an information processor, rests on the second law of thermodynamics, which is all about entropy: that is, the energy 'lost', usually in the form of heat, whenever one kind of energy is transformed into another. In their analysis, Parker and Walker revisited the heat engine concept which provided the foundation for the second law of thermodynamics and applied this to a computer. Based on their Carnot analysis, they developed a formula using processor temperature, bit rate and power consumptions as variables that can be used for comparing the absolute energy efficiency of any information processor on a logarithmic scale.