Abstract
Binary switches, which are the primitive units of all digital computing and information processing hardware, are usually benchmarked on the basis of their ‘energy–delay product’, which is the product of the energy dissipated in completing the switching action and the time it takes to complete that action. The lower the energy–delay product, the better the switch (supposedly). This approach ignores the fact that lower energy dissipation and faster switching usually come at the cost of poorer reliability (i.e., a higher switching error rate) and hence the energy–delay product alone cannot be a good metric for benchmarking switches. Here, we show the trade-off between energy dissipation, energy–delay product and error–probability for an electronic switch (a metal oxide semiconductor field effect transistor), a magnetic switch (a magnetic tunnel junction switched with spin transfer torque) and an optical switch (bistable non-linear mirror). As expected, reducing energy dissipation and/or energy–delay product generally results in increased switching error probability and reduced reliability.
Highlights
The primitive element of all digital circuits is a “binary switch” which has two stable states encoding the binary bits 0 and 1.Computing and digital signal processing tasks are carried out by flipping such switches back and forth between the two states
A larger ∆Q translates to both stronger error-resilience and better reliability. This makes it obvious that there is a direct relation between reliability and energy–delay product; if we reduce the energy dissipation or energy-delay product by reducing ∆Q, we will invariably make the switch less reliable
Using the values in Equations (5) and (6), we get that the minimum energy dissipation and the minimum energy–delay product that we can expect in this type of FET device, while maintaining minimum acceptable reliability, are ~10 aJ and 10−27 J-s, respectively
Summary
The primitive element of all digital circuits (i.e., for computing, signal processing, etc.) is a “binary switch” which has two stable states encoding the binary bits 0 and 1. Computing and digital signal processing tasks are carried out by flipping such switches back and forth between the two states. Delay product’, which is the product of the energy dissipated during switching and the switching time [1]. This approach, ignores the fact that usually the less energy we dissipate (or the faster we try to switch), the more error-prone the switch becomes. Any saving in energy or computational time gained by employing switches with a lower energy–delay product may be offset by the additional resources that would be needed for error correction.
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