Chris, Brent and meekerdb, While we have been considering optimizing the efficiency of circuitry and software, we neglected that while talking on the smartphone, 1/2 of the total power budget goes to radiation from the smartphone antenna - about 2 Watts as I remember. That will drain a typical smartphone battery in less than 3 hours, and there is not a lot we can do about it, except use the phone for all of it's other functions and don't talk too much! LWSterritt
On Sep 20, 2013, at 5:24 PM, meekerdb <meeke...@verizon.net> wrote: > On 9/20/2013 4:40 PM, Chris de Morsella wrote: >> Current software is very energy efficient -- and on so many levels. I worked >> developing code used in the Windows Smartphone and it was during that time >> that I had to first think hard about the energy efficiency dimension in >> computing -- as measured by useful work done per unit of energy. The >> engineering management in that group was constantly harping on the need to >> produce energy efficient code. >> >> Programmers are deeply engrained with a lot of bad habits -- and not only in >> terms of producing energy efficient software. For example most developers >> will instinctively grab large chunks of resources -- in order to ensure that >> their processes are not starved of resources in some kind of peak scenario. >> While this may be good for the application -- when measured by itself -- it >> is bad for the overall footprint of the application on the device (bloat) >> and for the energy requirements that that software will impose on the >> hardware. Another example of a common bad practice poorly written >> synchronization code (or synchronized containers). >> >> These bad practices (anti-patterns in the jargon) can not only have a huge >> impact on performance in peak usage scenarios, but also act to increase the >> energy requirements for that software to run. >> >> I think that -- with a lot of programming effort of course (which is why it >> will never happen) that the current code base, and not only in the mobile >> small device space, where it is clearly important, but in datacenter scale >> applications and service (exposed) applications as well -- that the energy >> efficiency of software has a huge headroom for improvement. But in order for >> this to happen there has to first be a profound cultural change amongst >> software developers who are being driven by speed to market, and other >> draconian economic and marketing imperatives and are producing code under >> these types od deadlines and constraints. > > There's a lot of bad design in consumer electronics, particularly in user > interfaces, because the pressure is to get more and newer features and apps. > Eventually (maybe already) this will slow down and designers will start to > pay more attention to refining the stuff already there. > >> >> If there is a theoretical minimum that derives from the second law of >> thermodynamics it must be exceedingly far below what the current practical >> minimums are for actual real world computing systems. And I do not see how a >> minimum can be determined without reference to the physical medium in which >> the computing system being measured is implemented. > > It is determined by the temperature of the environment in which entropy must > be dumped in order to execute irreversible operations (like erasing a bit). > But you're right that current practicle minimums are very far above the > Landauer limit and so it has not effect on current design practice. The > current practice is limited by heat dissipation and battery capacity. > >> >> In fact how could a switch be implemented without it being implemented in >> some medium that contains the switch? > > The way to completely avoid Landauer's limit is to make all operations > reversible, never lose any information so that the whole calculation could be > reversed. Then there's no entropy dumped to the environment and Landauer's > limit doesn't apply. > > 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 email@example.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 firstname.lastname@example.org. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.