Perpetual Computation Can it be done

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Perpetual ComputationCan it be done?

• By Antonis Antoniou

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Overview

• The Problem
• Perpetual Computation
• Adiabatic Computation
• Challenges
• Circuit Families
• Experimental Results
• Conclusion

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The Problem

• Perpetual X
• Can we have computations done without any energy
  consumption?

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The Answer

• Not really
• But we can get close
• And when we do we call it Adiabatic

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Why we care

• Less energy spend per computation
• Less weight to carry
• More uptime

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Why Adiabatic

• Difficult to scale voltage
• Threshold voltage causes problems
• Energy saving advantage
• Low EMI

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Perpetual ComputationThe Theory

• Two conditions need to be satisfied
• Reversibility of computation
• Adiabatic switching
• 2

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The TheoryContd

• Power consumption of classical circuit
• Power consumption of adiabatic circuit

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Adiabatic ComputationIn Practice

• Only one requirement
• Adiabatic Switching
• Engineering compromises
• Charge is recycled/recovered

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Challenges

• The clock power source
• Efficiency
• High speed gradual transitions (Tradeoff)
• Phases
• Circuit topologies
• Allow charge recovery
• Constant load
• Power management compatibility
• Signal Buffering

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Power Sources

• Use LC oscillators
• Efficient ( )
• Easy
• Design Procedure
• Calculate model parameters (R,C)
• Calculate L for desired frequency
• Simulate Generator

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Adiabatic Circuit FamiliesMultiple Phases

• Efficient Charge Recovery
• Logic (ECRL) 2N2P
• 1

• 2N-2N2P Positive
• Feedback Adiabatic Logic (PFAL)
• 1

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Multiple PhasesContd

• Timing Diagram for ECRL
• 3 2
• Phase Diagram for ECRL
• 2

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Two Phases

• Pass-Transistor Adiabatic Logic (PAL)
• 1
• 4

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Two PhasesContd

• Timing Diagram for PAL
• 4

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Single Phase

• True Single-Phase
• Energy-Recovering Logic
• (TSEL)
• 1

• Source Coupled Adiabatic
• Logic
• (SCAL)
• 1

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Single PhaseContd

• Timing Diagram for SCAL
• 1

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AdvantagesComparison of Families

• WARNING
• 1

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Comparison of Families Contd

• 4

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Comparison of Families Contd

• 3

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Comparison of Families Contd

• 3

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Conclusion

• Adiabatic Circuits are feasible
• Hard to implement
• Very good efficiency once implemented
• Still a niche market

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A piece of advice

• Just because it is published it does not mean it
  is correct
• 7

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Bibliography

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