On 1/1/2024 will I think J. Cannell is right about the minimal energy per bit-meter of interconnect?
12
1.3kṀ2611
resolved Jan 15
Resolved
N/A

Jacob Cannell seems to make the following claims in a LessWrong post:

A non-superconducting electronic wire (or axon) dissipates energy according to the same Landauer limit per minimal wire element. Thus we can estimate a bound on wire energy based on the minimal assumption of 1 minimal energy unit Eb per bit per fundamental device tile, where the tile size for computation using electrons is simply the probabilistic radius or De Broglie wavelength of an electron[7:1], which is conveniently ~1nm for 1eV electrons, or about ~3nm for 0.1eV electrons. Silicon crystal spacing is about ~0.5nm and molecules are around ~1nm, all on the same scale.

Thus the fundamental wire energy is: ~1 Eb/bit/nm, with Eb in the range of 0.1eV (low reliability) to 1eV (high reliability).

[...]

Estimates of actual brain wire signaling energy are near this range or within an OOM[19][20], so brain interconnect is within an OOM or so of energy efficiency limits for signaling, given its interconnect geometry (efficiency of interconnect geometry itself is a circuit/algorithm level question).

This resolves YES if I am convinced of all of the following claims by Jan 1, 2024, and NO if I think one has been convincingly disproven.

  • The energy Eb required to transmit information in a microscopic "nonreversible" wire at error rate 10^-15 is greater than 0.3 eV / bit / nm, regardless of speed, voltage, etc.

  • Wires inside modern CPUs, wires connecting CPU to memory, and axons are all "nonreversible" in this sense.

  • Axons get within 1.5 OOM ("an OOM or so") of Eb.

  • The required energy only decreases about logarithmically with wire size; you cannot for example get 100x better efficiency with 1cm thick wires than with 1nm thick wires.

I've spent about 5 hours trying to understand this so far and am currently around 60%. The bottleneck is some combination of not knowing enough physics and not having an intuitive explanation. I will spend at least another 30 minutes or $100 sometime in 2023.

This question wording may change before March 1, 2023 in a way that preserves the spirit of the question. I will not trade in this market.

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