Okay I am beginning to get the reasoning... some heat must be lost, inevitably dispersed, increasing entropy when the bit of information contained by the system is erased. Am still not clear how Landauer computed the formula "kT ln 2" -Chris

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________________________________ From: meekerdb <meeke...@verizon.net> To: everything-list@googlegroups.com Sent: Friday, September 20, 2013 4:37 PM Subject: Re: What gives philosophers a bad name? On 9/20/2013 1:22 PM, Chris de Morsella 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 byover a trillion times in 54 >years." > >Size (or rather the lack of it) matters in this equation. > But there still a limit because entropy has to be dumped into the environment, which is not at 0deg, if a register is to be erased. http://en.wikipedia.org/wiki/Landauer%27s_principle But we are many orders of magnitude from the Landauer limit now - lots of room for improvement. Brent -- 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.