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Boosting Battery Life For RISC Processors

Posted by ryuzaki0 on from the staying-unplugged-longer dept.

prostoalex writes "National Semiconductor and ARM Holdings will jointly develop the power management solution for RISC chips, that they estimate will improve battery life by 25-400%. The target date of the first sample product is Q2 2003." My old Tadpole laptop sure could have used this. I counted myself as lucky when I got a whole 45 minutes out of a battery.

12 of 113 comments (clear)

  1. Great move! by e8johan · · Score: 5, Insightful

    When developing portable devices the most limiting factor today is not processing resources, memory or anything such. It is simply the power source.

    Batteries of today are either too weak or too heavy. How ofter does one have to choose between a slim-line battery or an ultra-long life.

    There have been many suggestions for competing technologies such as fuelcells, harvesting of motion energy and solar cells to mention a few. But still, they have proven to be too expensive, large or have some other problem (such as not being ready for production use yet). Hopefully these one of these, or any other, portable power sources will make it possible to carry real computing power without having to carry a heavy battery pack.

    The solution today is to reduce the power usage. This can be done by shutting down parts of the clock trees in the CPUs, or by using Intel's PowerStep (i.e. two working speeds), or Transmetas's variable voltage and frequency technology, LongRun. As the article lacks technical details we can only guess about the techniques used behind the PowerWise solution. Also, the figures 25-75% efficiency gain is most probably measured under special conditions.

    But, in order to avoid sounding too negative, it seems like the industry has realized the problem and are working for a solution. I feel that most of today's solutions (power saving) are just a cure for the symptoms (bad battery time), not for the cause (bad battery technology).

    1. Re:Great move! by clickety6 · · Score: 4, Insightful

      Perhaps another approach would be to reduce requirements on the PC power by writing software that is less bloated and more efficient and is geared towards a portable solution. There really should be no need for my laptop to have a 1 Ghz chip just to run some word processing and spreadsheet software. Nor should the computer need 250 Megs of memory just to start up and run some windows. We should eb using nutcrackers to crack our nut, not a pile driver!

      --
      ----------------------------------- My Other Sig Is Hilarious -----------------------------------
    2. Re:Great move! by wheany · · Score: 1, Insightful

      But does the CPU really consume that much energy? Hasn't the biggest power hog always been backlit displays and disk drives?

    3. Re:Great move! by e8johan · · Score: 3, Insightful

      "dont expect the battery life of a portable device improve by 100% when the power the CPU consumes goes down by 50%"

      I don't, but Amdahl's law apply here too, reduce the biggest factor. You probably get a better yeild if you attach the CPU than any other device. These companies tend to evaluate the problems before attacking them (even though it doesn't seem so all the time).

    4. Re:Great move! by SmittyTheBold · · Score: 4, Insightful

      The solution today is to reduce the power usage. This can be done by shutting down parts of the clock trees in the CPUs, or by using Intel's PowerStep (i.e. two working speeds), or Transmetas's variable voltage and frequency technology, LongRun. ...or, by using an architecture that does not require as many useless (er...extra) transistors and is therefor more efficient to begin with. Witness the PowerPC, for example. In particular, the G3 is amazingly efficient in the desktop form.

      Compare, for example, the G4 at 11.5 million transistors, (I am not sure about the current G4e) and the P4 at 42 million (once again, this is an old number - recent P4s may have a different count). Is it any mystery, then, why the G4 uses so little power in comparison?

      I'm not discounting your ideas totally here - I'm just saying there is more to saving energy than throttling the CPU.

      In response to your last line - "most of today's solutions (power saving) are just a cure for the symptoms (bad battery time), not for the cause (bad battery technology)" - I have to say that although batteries are a hindrance, they are not much of one at the moment. Portables currently dissipate quite a bit of heat. If you increase the power they use (and increase the power given to them) you increase heat output, which is bad. Current laptops are about like holding a lightbulb against your lap. Are you sure you want that to be increased?

      The real limits with laptops these days have more to do with dissipating the heat they already produce than powering that mess. Upgrading batteries is not a solution to this, while more efficient processors are.

      --
      ± 29 dB
    5. Re:Great move! by SmittyTheBold · · Score: 3, Insightful

      I'm not saying (or at least didn't intend to say) that the G4 is a perfect architecture, not that is has no room for improvement. I'm just suggesting that performance tweaks like those used in the P4 are a bit like worrying about the aerodynamics of your '57 Chevy. Sure, you can add a bit of fuel efficiency, but there are far greater gains to be had.

      --
      ± 29 dB
    6. Re:Great move! by jonbrewer · · Score: 3, Insightful

      by writing software that is less bloated and more efficient and is geared towards a portable solution.

      Last I checked, the older versions of WordPerfect still worked... And there's always vi. :-)

  2. they turn off when getting alot of NoOP'S by johnjones · · Score: 1, Insightful

    come on people

    you just turn off the part of the core when you dont need it

    not a really taxing idea (transmeta intel MOT and IBM all do the same in various ways)

    but putting anything to silicon is always hard so kudos

    john 'MIPS' jones

  3. Re:More detail at ARM's web page by doug363 · · Score: 3, Insightful
    Certainly, even a huge reduction in processor power usage probably won't do anywhere near that much for overall power usage. However, they're anticipating a massive blowout in power usage by the phone's microprocessor in the next few years. As I'm sure you're aware, there's a move towards adding all sorts of significant enhancements: video conferencing, larger colour screens, interactive content, etc. They think that this could increase processor power usage by up to 10 times without some sophisticated power management. I don't know accurate this is, but since this stuff is probably aimed at ARM's customers, i.e. mobile phone designers, I'd guess that they'd better provide some significant saving in overall power usage before anyone would use it.

    I'm not sure on what the transmitter's power requirements are like with 3G phones, or (hypothetically) ultra wideband phones... Does anyone know how they compare to GSM phones? I know that the max allowed transmitter power of a GSM phone varies a lot between countries.

  4. Re:Asynchronuous logic? by KeggInKenny · · Score: 3, Insightful
    I know that the University of Manchester was designing an asynchronous Arm-binary compatable processor (here). Now that is has been shown to be feasable to do RISC in asynch, maybe big vendors will start to take notice.

    A bit of (greatly simplified) background for those who havn't looked into this. The huge decrease in asych power consumption (at least using CMOS) is becasue the MOSFETs discipate (sp?) power during voltage level changes. Many transisters in sychronous chips change state every clock pulse, but changes are much more isolated in asynchrouns chips. I predict (in my infinite wisdom, and using my crystal-ball-of-infinite-wisdom) that RISC based asynch will get much more powerful and fast as companies like Intel, Motorola, etc put more money into reasearching this previously forgotten/niche field.

    Probably they'll only be used in portable systems at first to conserve power, but maybe if design techniques progress, we'll see them in desktop PCs or even some heavy metal systems within 10 years or so as other benifits becom apparent... But even my crystal-ball can't say for sure.

    -- below is opinion, don't read it if you're an easilly offended Republican or supporter thereof as you may be unintentionally offended - damn -1 flaimbait modders... --
    I wouldn't count on much (US) government research money or grants going into it while Bush is president though... I don't exactly think he's interrested in energy conservation...

    --

    "A dictatorship would be a heck of a lot easier, there's no question about it." -George W. Bush
  5. Re:Asynchronuous logic? by e8johan · · Score: 5, Insightful

    Another advantage of the ARM is the Thumb instructions that reduces the traffic over the memory bus. We must remember that driving memory bus is an expensive operation (power wise) compared to finding data in the cache. Smaller code means more code in the cache. One problem is that multimedia applications (such as movies, music, etc) fails to utilize the cache well (since the data isn't re-accessed). This is a problem area that needs more research.

  6. The title doesn't make sense.... by UrGeek · · Score: 2, Insightful

    ...Batteries don't care if your CPU is RISC, CISC, chicken feathers, or satin. Would a better title be, "Reducing power use in RISC, to save battery life"?