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<div>On Jun 7, 2014, at 7:26 PM, Anders Sandberg <<a href="mailto:anders@aleph.se">anders@aleph.se</a>> wrote:</div>
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<div><span data-mailaddress="rhanson@gmu.edu" data-contactname="Robin D Hanson" class="clickable"><span title="rhanson@gmu.edu">Robin D Hanson</span><span class="detail"><span class="Apple-converted-space"> </span><<a href="mailto:rhanson@gmu.edu">rhanson@gmu.edu</a>></span></span><span class="Apple-converted-space"> </span>,
7/6/2014 6:20 PM:<br>
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I know that people often say things like this, but I think it gets the physics wrong. The real resource is negentropy. One just stores that in a form of free energy, but how many bits one can erase later with that negentropy doesn't depend on the temperature
later, at least to first order. One will want to do reversible computing later, and that isn't necessarily much more efficient at lower temperatures.</div>
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<div>Hmm... how does this actually work? You make a lot of negentropic stuff, and when you need to erase a bit in a late era you use the negentropy to mop up the bit entropy? But the energy cost of making the negentropy/free energy stuff in the early era seems
to be significant. <br>
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<div>When you are designing reversible computing systems, you are focused on making each small part individually be nearly reversible - you have to drive it in some direction via some deviation from full reversibility, but that cost is an entropy cost - the
process can work fine at lots of different temperatures. To get free energy to run this process, you use your negentropy store to create it, as one usually does in thermodynamic system design. And when have to do error correction and to erase bits, you primarily
focus on moving bits reversibly from your system into the negentropy store. The resource that you fundamentally have in your storage is negentropy. It can be stored in different ways and converted between those ways, but the way to count it is as negentropy.</div>
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<div style="font-size: 12px; ">Robin Hanson <a href="http://hanson.gmu.edu">http://hanson.gmu.edu</a><br>
Res. Assoc., Future of Humanity Inst., Oxford Univ.<br>
Assoc. Professor, George Mason University</div>
<div style="font-size: 12px; ">Chief Scientist, Consensus Point<br>
MSN 1D3, Carow Hall, Fairfax VA 22030<br>
703-993-2326 FAX: 703-993-2323</div>
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