Chris, It's the Landauer argument relating energy to information, as Frank wrote. There is a summary article in the same issue of Nature: Philip Ball, "The unavoidable cost of computation revealed," Nature (March 07, 2012). Ball references the analysis mentioned in my last post; It's the ultimate thermodynamic limit, and how close we approach that limit will depend upon technology as you discuss. Intel, Apple and others are making significant improvements in the efficiency of their chip sets, but there is never enough battery life in a smart phone. LW

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On Sep 20, 2013, at 2:40 PM, Chris de Morsella <cdemorse...@yahoo.com> wrote: , > Interesting. Do you know what assumptions went into their analysis? > > I would think that this is a medium dependent value; i.e. what underlying > medium is the relying on to hold its logical state. Did the researchers > attempt to figure out the minimum scale system (say an electron spin for > example in a spintronics device -- which have not yet been built, but which > is very much one of the future paths to the ever more small scale and which > is sucking down big R&D money to try to find an economic means of building > the single electron type gates that would rely on the electron's spin. > > What if some hypothetical future technology is able to access more > fundamental sub-atomic systems and a logic state is able to be contained in > something far smaller than an electron. I am speculating here of course > because such technology does not exist (as far as I know), but what if a > state could reliably be inferred -- even if not directly measured -- in > something that begins to approach the Planck scale -- say some property of a > vibrating string. Wouldn't the minimum energy to flip a bit, in this new > hypothetical and vastly smaller scale circuit be considerably less (by many > orders of magnitude) than the energy required to flip a macro gate (which by > comparison even the most miniaturized transistor would be)? > > My point in replying is that the medium and the scale in which the logic is > etched (or some equivalent process for non-lithography based production) are > other drivers that need to be considered, and that lower energy does not > necessarily equate to slower performance. The twenty watt human computer can > solve (especially subtle pattern recognition) problems that bring a > super-computer to its knees; admittedly this is changing as computer > hardware/software improves and better pattern recognition algorithms are > developed, but our energy frugal computing machines cannot be said to be slow > -- yes I know nerve impulses travel at a vastly reduced speed as compared to > electrons flipping logic circuits, but the brain is a massively parallel > architecture and is performing thousands maybe millions of tasks each and > every second. > > -Chris > From: L.W. Sterritt <lannysterr...@comcast.net> > To: everything-list@googlegroups.com > Cc: L.W. Sterritt <lannysterr...@comcast.net> > Sent: Friday, September 20, 2013 1:50 PM > Subject: Re: What gives philosophers a bad name? > > > Chris, > An article in Nature last year presents a calculation of the theoretical > minimum energy required to erase a bit - independent of the computer: >> >> Antoine BĂ©rut, Artak Arakelyan, Artyom Petrosyan, Sergio Ciliberto, >> Raoul Dillenschneider & + et al. >> Nature 483, 187-189 doi:10.1038/nature10872 > L.W.Sterritt > On Sep 20, 2013, at 1:22 PM, Chris de Morsella <cdemorse...@yahoo.com> wrote: > >> >> A computation always takes a nonzero amount of energy to perform, >> >> theoretically you can make the energy used be as close to zero as you >> >> like, but the less energy you use the slower the calculation. >> How does that square with the increased (well measured) energy efficiency >> per fundamental unit of logic (single machine operation) -- it takes far >> less energy to perform an elementary logic operation on a modern CPU than it >> did on say a CPU from ten years ago (even if the modern CPU may suck down >> more total power -- it is performing far more work) >> >> Modern CPUs clearly are also operating at much higher speeds. I think you >> are not factoring in the dimension of scale or the physical size of the >> logic container/state-machine. As the size of a logic gate is scaled down it >> takes less energy and can operate at a higher clock speed. >> >> http://en.wikipedia.org/wiki/Performance_per_watt >> "For example, the early UNIVAC I computer performed approximately 0.015 >> operations per watt-second (performing 1,905 operations per second (OPS), >> while consuming 125 kW). The Fujitsu FR-V VLIW/vector processor system on a >> chip in the 4 FR550 core variant released 2005 performs 51 Giga-OPS with 3 >> watts of power consumption resulting in 17 billion operations per >> watt-second.[1][2] This is an improvement by over a trillion times in 54 >> years." >> >> Size (or rather the lack of it) matters in this equation. >> -Chris >> >> From: John Clark <johnkcl...@gmail.com> >> To: everything-list@googlegroups.com >> Sent: Friday, September 20, 2013 10:38 AM >> Subject: Re: What gives philosophers a bad name? >> >> On Thu, Sep 19, 2013 at 6:10 PM, LizR <lizj...@gmail.com> wrote: >> >> >> As Rolf Landauer said "Computation is physical", all computations must >> >> use energy and generate heat. And what's the difference between a >> >> physical process and a non-physical process anyway? >> >> > I thought it was only erasing the results of computations that had to use >> > energy and increase entropy? - if so - quibbling, I know, but sometimes >> > quibbles have important consequences. >> >> A computation always takes a nonzero amount of energy to perform, >> theoretically you can make the energy used be as close to zero as you like, >> but the less energy you use the slower the calculation. >> >> John K Clark >> >> >> >> >> >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Everything List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to mailto:everything-list%2bunsubscr...@googlegroups.com. >> To post to this group, send email to everything-list@googlegroups.com. >> Visit this group at http://groups.google.com/group/everything-list. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Everything List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to everything-list+unsubscr...@googlegroups.com. >> To post to this group, send email to everything-list@googlegroups.com. >> Visit this group at http://groups.google.com/group/everything-list. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Everything List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to everything-list+unsubscr...@googlegroups.com. >> To post to this group, send email to everything-list@googlegroups.com. >> Visit this group at http://groups.google.com/group/everything-list. >> For more options, visit https://groups.google.com/groups/opt_out. > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > > > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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