Battery Life & Power Analysis

The final unknown in all of this is power consumption. ARM's Cortex A15 isn't really supposed to be a sipper of power, and when placed in a notebook I don't know that there's a lot we can conclude about how it stacks up to Atom either. Some high level power consumption data would normally help but these two platforms are fairly different:

Samsung Chromebook Power Consumption Comparison
Display @ 200 nits Idle Kraken (Avg) Kraken (Peak)
Samsung Chromebook 500 (Atom N570) 11.53W 14.4W 15.2W
Samsung Chromebook 303 (Exynos 5 Dual) 6.33W 10.5W 11.3W

The new Chromebook consumes considerably less power at idle than its predecessor. The smaller display, simplified motherboard and truly integrated SoC platform are likely all to thank for this. The significant reduction in power also helps explain the big reduction in battery capacity as well.

Under load, the two platforms do see differing levels of additional power consumption. The new Exynos 5 based Chromebook sees a dramatic increase in power consumption under load, hitting 10.5W (a 66% increase over idle) while running Mozilla's Kraken benchmark. The Atom N570 based Chromebook increases power consumption as well, but just not by as significant a degree: ~25%. This actually helps illustrate exactly why Atom wasn't phone worthy in its earlier incarnations. Contrary to popular belief, it wasn't actually peak power consumption that was the problem (a move to 32nm can easily eat into these numbers). The total platform power consumption, particularly at idle, was Atom's real problem in the early days. It also turns out that this is much of what keeps Intel's Core processors from moving into ultra mobile form factors, something that Haswell is supposed to address.

Given that we're dealing with somewhat different panels here, I wanted to see what power consumption looked like if we removed the panels from the equations. I re-ran all of the power data with the display turned off:

Samsung Chromebook Power Consumption Comparison
Display Off Idle Kraken (Avg) Kraken (Peak)
Samsung Chromebook 500 (Atom N570) 8.82W 11.4W 12.4W
Samsung Chromebook 303 (Exynos 5 Dual) 4.07W 8.32W 9.27W

The old Atom based Chromebook uses more than twice the idle power of the new version - it's no wonder Google was able to get away with a battery half the size. Once again however we see a much larger increase in power consumption once the Cortex A15 is under heavy load. Active power consumption more than doubles on the new Chromebook, while we see around a 30% increase on the Atom based system. I do wonder what will have to be done to get the Exynos 5 Dual into a smartphone as an increase of ~4W under load just won't cut it in a phone. The Atom platform shows a 2.6W increase in power under load, which sounds about right for a high clocked 45nm part.

Web Browsing Battery Life

Despite the more power efficient platform, the reduction in battery capacity puts the new Chromebook well below the Atom model in battery life. Our wireless web browsing test put the new Chromebook at just over 6 hours of continuous use on a single charge. For a notebook that's not too bad, but compared to modern tablets it's not good.

The performance gains over Atom (and by extension, the ARM Cortex A9) do give us some indication as to what could be done to get Exynos 5 into a smartphone. By dropping clocks much lower than 1.7GHz Samsung would be able to maintain a performance advantage in a very power constrained device and hopefully keep power in check. The photo above features a list of all of the voltage levels supported by Samsung's Exynos 5 Dual as implemented in the new Chromebook.

Performance: Atom vs. ARM's Cortex A15 Final Words
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  • extide - Wednesday, October 31, 2012 - link

    Yeah, basically this next gen 22nm Atom core is going to be make it of break it for the Atom. I can see the Atom getting canned entirely if the 2nd gen core on 22nm sucks. Reply
  • andrewaggb - Wednesday, October 31, 2012 - link

    Yeah, intel must be feeling crazy pressure. They are 6-12 months behind. Both Haswell and the new atom should be coming out now with windows 8. Reply
  • amdwilliam1985 - Wednesday, October 31, 2012 - link

    I'm impressed by the ARM performance, besides the performance and battery life, there is also the cost to consider. As far as I know, ARM cpu cost much less than x86 cpu.
    If I can get 50% of power for 25% of the price, that sounds like a good trade off in many scenarios.
    Reply
  • wsw1982 - Thursday, November 01, 2012 - link

    The samsung arm a15 is basically a 6+ w SOC... If you linear scale the medfield up 3 times, it means a three core atom, and three times the graphic power (does scale linearly), and i think the performance is comparable. The medfeld is arround 64 mm2, and the three core atom and graphic is, to my best guess, 100mm2, any one give me a estimation of the die size of the samsung a15? we can calculate the price :) Reply
  • krumme - Friday, November 02, 2012 - link

    The intereting thing is the total cost for the OEM. The A15 implemented as here must be dirt cheap.

    Intel have high fixed cost, but arm can spread the cost to phones whatever through both Samsung but primarily TSMC.

    In the long run it will be difficult for Intel the have the same low cost.

    Years back they could use old fab equipment for the Atom and in that way use production capacity that had been written off the the worst part. Today they they need the new process nodes to be competitive, and that will raise cost for the Atom. I think they are in a bad market here.

    Competing with TSMC and Samung is another world from competing with AMD and GF.

    They need their ultrabooks, but the market is to small for the future fab cost.

    Now arm can share cost from phones to notebooks. That is massive cost advantage imho.
    Reply
  • mayankleoboy1 - Wednesday, October 31, 2012 - link

    A chromebook is too niche a product to properly judge a SoC . Typically thermals are completely different.
    Its fast, yes, but how will it do in a smartphone ? And chromeOS has too few apps and the chromebook has too less a res to actually judge the best SoC .....
    Reply
  • Krysto - Thursday, November 01, 2012 - link

    Not like the Atom one was using bigger resolution. And Exynos 5 Dual can support up to 2560x1600, as we've already seen with Nexus 10. Reply
  • MilwaukeeMike - Wednesday, October 31, 2012 - link

    Maybe I missed it, but does this have a built in webcam? Looks like it does from info on other sites, and I'd like to know how it performs for Skype purposes if anyone knows. Sounds like videos from youtube/facebook work ok as well, which would make this a great netbook style option. Reply
  • deneb - Wednesday, October 31, 2012 - link

    For that price, why wouldn't anyone get a used laptop instead? At least then they'll get the benefit of a proper OS of their choice (linux or Windows, i don't know if used apple lappies go that low).

    Granted, it wouldn't be new, but at least it would be many times more functional - no? :)
    Reply
  • Midwayman - Wednesday, October 31, 2012 - link

    Battery life. A old low end laptop is going to have terrible battery life. Reply

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