Paul, Richard, thanks a lot for your extensive replies, much appreciated! :-)
I probably won't be able to finish my slides before Sunday but I'll try and send you a draft if I can find an Internet connection during my Munich-Copenhagen-Stockholm train adventure... Cheers, Christoph On Thu, Nov 12, 2009 at 7:22 AM, Richard A. Smith <rich...@laptop.org>wrote: > > > Now while the original goal of getting the XO-1's power consumption down > to > > 2W wasn't achieved it's still a pretty lean and efficient machine. > > In my power talks I give during country meetings I mention that if you see > reference to a number for XO power usage that does not _specifically_ > indicate the usage during the measurement period then its wrong. > > There are several usage modes where the XO-1's power draw is < 2W and even > less than 1W. > > 5 of the 7 modes I describe in the link below draw less than 2W. > > http://wiki.laptop.org/go/XO_power_draw#Modes > > What I suspect you mean here is the average power consumption for a average > user with aggressive power saving mode disabled. Which yes is above 2W. > Its 4W-7W. > > If I seem a bit anal about that its intentional. The reason is that in the > past its not been clear that these power numbers discussed were for the low > power modes and not the holistic average power draw. I've had to deal with > several deployments (small and larger) or test sites that have budgeted for > 2W (or some other odd number) of power and then get all cranky when I > mention that charging the battery pulls 17W. > > Granted they should have checked but after its gone through 3 people > speculation seems to turn into fact. > > So I try to very clear and specific when I talk about power usage to help > try stop that from happening in the future. > > > obviously plan to talk about the choice of hardware components and MLJ's > > display design. Another topic I'll touch upon is the wide-range voltage > > input which allows for a variety of power sources to be used without > > requiring further external regulation. > > 18V max. [1] Gen 1-5 opens that up to 24V. > > [1] Empirically you can get between 20-22V but allowing for the tolerances > of the parts the guaranteed minimum is 18V > > > One thing I'm less sure about is the DCON because I'm don't know how > > aggressively it is currently being used (maybe someone can shine a light > on > > this, I didn't find anything about it on the wiki or the mailing > > By DCON do you mean DCON mode or frozen. Where the screen holds its last > value the cpu gets turned off? If so then its available in the latest XO-1 > build. Right click on the center XO guy and select control panel then > select power. There is an option for enabling "Automatic power management" > and its listed as experimental. If you set that your system auto suspend > when and activity timer expires. > > The knobs for the activity timer can be found in > /etc/ohm/plugins.d/timeouts.ini One of them controls when the backlight is > dimmed the the other when suspend happens. Units are ms. If you set them > really low you will roughly get the "in between keystrokes" behavior. > Except that resume with WLAN takes around 900ms. The drawbacks are that > some of your networking apps won't work 100% like they did with the system > up all the time and sometimes the WLAN device refuses to talk on the USB bus > any more (USB 3 strikes error). > > > list). Another question I'm interested in is what the efficiency of the > > AC-DC adapters shipped with the XO-1 is? > > The ultimate eff% depends on the line voltage, line frequency, load, and > ambient temperature. Its expressed as a series of curves. See my statement > above about referring to power with single-across-the-board numbers. Unless > you are in the lab you are guaranteed to be wrong. > > That said Energy Star attempts to reduce all that down to a class number by > taking the average of 4 points spread on the curves. [2] Our class rating is > IV which says that the adapter has an average efficiency of >= 75%. > > [2] We are on an older energy star spec. The latest energy star spec rev > 5.0 (Active July 1, 2009 ) has higher requirements. > > > I'm also wondering whether it makes sense to talk about some of the ideas > > discussed in the early stages of the project (e.g. suspend inbetween > > key-strokes which IIRC ended up not being implemented). > > Certainly. Please do. These are very much still goals. Right now the > focus is on XO-1.5 where we hope to have bypassed some of the issues that > gave us trouble in XO-1. Then we can start work on making the networking > apps and the timer subsystems play nice with turning off a CPU. When thats > all done then someone can look at if it makes sense to try and back port > stuff to XO-1. > > Turning off CPU+Companion chip (or dropping it into non-functional but > really low power mode) but still having a system that functions normally has > the potential for large amounts of power savings. > > Consider my laptop where I run my IRC client. I leave it running so that > people can ping me on IRC. There are many periods when I'm not actively > using it. During that time its basically just wasting power. If 90% of the > devices could be turned off yet wake back up briefly to catch IRC messages > it would save _lots_ of power. My AC power meter tells me that my laptop > sitting here with my various apps open but me not typing draws 17-19W from > the grid. That could be reduced to 2W. > > > As I said it's only a short talk (10min max.) but there's anything else > > significant when it comes to the power consumption and underlying design > > that I've left out above then please give me a shout. > > I think OLPC's philosophy is significant. The XO is the lowest power > laptop of its class. But its still off by about a factor of 10 from whats > needed in places with no power infrastructure. > > Designing for low power seems to still be a foreign concept to the PC > world. The current method of getting longer battery life appears to be add > a larger battery. Quoting Ed McNierney "How big does your battery have to > be when there's nowhere to plug it in?" > > Hope this helps. > > -- > Richard A. Smith <rich...@laptop.org> > One Laptop per Child > -- Christoph Derndorfer co-editor, olpcnews url: www.olpcnews.com e-mail: christ...@olpcnews.com
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