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Does this imply that physical entropy and informational entropy are the same? Does it imply the computer would not give off heat? Or that a significant amount

by sadgit 9y ago

Does this imply that physical entropy and informational entropy are the same? Does it imply the computer would not give off heat? Or that a significant amount of the heat generated by a computer is due to information loss?

SilasX 9y ago
>Does this imply that physical entropy and informational entropy are the same? It does, and there is a very strong (but not universally accepted) case that they are the same thing: https://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory https://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_... Great lay article about it: http://lesswrong.com/lw/o5/the_second_law_of_thermodynamics_and_engines_of/ http://lesswrong.com/lw/o5/the_second_law_of_thermodynamics_... (Side note: I've long thought you can derive Carnot efficiency based on information-theoretic arguments about the information contained in knowing only the temperature difference between a heat source and a sink.) >Does it imply the computer would not give off heat? Or that a significant amount of the heat generated by a computer is due to information loss? Basically, yes. You can't avoid the heat emission from setting a 0 to a 1 on that computer's storage medium, but you would avoid the loss from any of the intermediate computations that typically make CPUs so hot.
- socmag 9y ago
  I'm not the person who was asking, but thanks for the insightful comments. Makes sense. Wouldn't a reversible computer that executes need to take up an exponentially large amount of physical space as it executes? That might work for small problems but it doesn't seem like it would scale. Or rather, it would scale to fill the known universe. Sorry I haven't really dug into the attached articles yet, but I will.
  - SilasX 9y ago
    See the thread about the asymptotic penalties: https://news.ycombinator.com/item?id=14151390 https://news.ycombinator.com/item?id=14151390
hcs 9y ago
> Does it imply the computer would not give off heat? The implication goes the other way: if the computer does not give off heat, it must be reversible.
- sadgit 9y ago
  So, in a sense, heat is unrecoverable information.
  - hcs 9y ago
    In some sense that seems to be true. But I just meant that while it's easy to make a reversible circuit, no tech we have today can make it as energy efficient as might be theoretically possible.

by sadgit 9y ago

SilasX 9y ago

>Does this imply that physical entropy and informational entropy are the same? It does, and there is a very strong (but not universally accepted) case that they are the same thing: https://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory https://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_... Great lay article about it: http://lesswrong.com/lw/o5/the_second_law_of_thermodynamics_and_engines_of/ http://lesswrong.com/lw/o5/the_second_law_of_thermodynamics_... (Side note: I've long thought you can derive Carnot efficiency based on information-theoretic arguments about the information contained in knowing only the temperature difference between a heat source and a sink.) >Does it imply the computer would not give off heat? Or that a significant amount of the heat generated by a computer is due to information loss? Basically, yes. You can't avoid the heat emission from setting a 0 to a 1 on that computer's storage medium, but you would avoid the loss from any of the intermediate computations that typically make CPUs so hot.

socmag 9y ago
I'm not the person who was asking, but thanks for the insightful comments. Makes sense. Wouldn't a reversible computer that executes need to take up an exponentially large amount of physical space as it executes? That might work for small problems but it doesn't seem like it would scale. Or rather, it would scale to fill the known universe. Sorry I haven't really dug into the attached articles yet, but I will.
- SilasX 9y ago
  See the thread about the asymptotic penalties: https://news.ycombinator.com/item?id=14151390 https://news.ycombinator.com/item?id=14151390

hcs 9y ago

> Does it imply the computer would not give off heat? The implication goes the other way: if the computer does not give off heat, it must be reversible.

sadgit 9y ago
So, in a sense, heat is unrecoverable information.
- hcs 9y ago
  In some sense that seems to be true. But I just meant that while it's easy to make a reversible circuit, no tech we have today can make it as energy efficient as might be theoretically possible.