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 <[email protected]> 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 [email protected]. > To post to this group, send email to [email protected]. > 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
