Idle Power

In all of these tests you're going to see three charts. The first will show you total platform power, measured at the battery, taking into account everything from SoC to display. The next shows you power measured at the CPU power delivery circuit, and the third shows you power measured at the GPU power delivery circuit. All values are measured in watts, and are reported in 15ms intervals (although I sampled at 1KHz then averaged down to 15ms).

For our first set of tests I simply wanted to get a feel for idle power. Both systems had all background syncing suspended, WiFi was connected, and we're just sitting at the Windows RT/8 Start Screen until the tablets reached a truly idle state. Note that idle under Windows RT/8 technically doesn't happen until the live tiles stop updating, which you'll see denoted by a drop in the idle power consumption in the graphs below.

First up is total platform power consumption:

Surface RT has higher idle power, around 28% on average, compared to Acer's W510. The last half of the graph shows the tablets hitting true idle when the live tiles stop animating.

A look at the CPU chart gives us some more granularity, with Tegra 3 ramping up to higher peak power consumption during all of the periods of activity. Here the Atom Z2760 cores average 36.4mW at idle compared to 70.2mW for Tegra 3.

The GPU specific data is pretty interesting - the GPU power rail shows much high power consumption than on Intel's Z2760. As I didn't design Tegra 3, I don't know what else is powered by this rail - although you'd assume that anything else not in use would be power gated. Imagination Technologies' PowerVR SGX 545 does appear to be quite power efficient here, on average using 155mW while rendering the Start Screen.

I wasn't happy with the peaks we were seeing when nothing was happening on the systems, so to confirm that nothing funny was going on I threw both tablets into airplane mode and waited for full idle. Check out the tail end of the platform power diagram:


That's much better. Without the AP talking to each tablet's WiFi radio constantly, idle becomes truly idle. If you're curious, the power savings are around 47.8mW (average) for the W510 in airplane mode when fully idle.

The GPU rail feeding the Atom Z2760 appears to hit a lower idle power when compared to NVIDIA's Tegra 3. Advantages in idle power consumption are key to delivering good battery life overall.

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  • Exodite - Tuesday, December 25, 2012 - link

    I think it's probably a fair guess that Apple has planned to converge their mobile and traditional computer business to the same hardware platform for some time.

    It's just not going to be x86.
  • wsw1982 - Tuesday, December 25, 2012 - link

    However, the fact is the ATOM can emulate the ARM with similar performance, but not the other way around. It will be interesting to see apple fully commit to netbook level performance.
  • StevoLincolnite - Tuesday, December 25, 2012 - link

    Software compatibility isn't that big of a deal either as Intel showed us Binary Translation awhile ago allowing Medfield to run x86 and ARM instructions.
  • krumme - Monday, December 24, 2012 - link

    I think this just proves Intels business is not tailored for the new low cost mobile market. A9 on low cost 40nm eats Atom for breakfast each and every day on the market -fact- and A15 will do exactly the same on dirt cheap 28nm.
  • tipoo - Monday, December 24, 2012 - link

    I think we read different articles. Atom is rather competitive. It is not eaten for breakfast by 40nm ARM parts.
  • yyrkoon - Tuesday, December 25, 2012 - link

    depends on how you look at it. Find me an atom based 7" tablet for $200. Such as the Nexus 7 ( which many regard as the best tablet in its class )
  • p3ngwin1 - Tuesday, December 25, 2012 - link

    like i said in another comment here, you can get Chinese tablets running Android 4.1 with 1.6Ghz Dual-Core ARM processors with Mali400 GPU's (good enough for many) with 7" 1280x720 screens, etc all for less than $150.

    the chips are usually Allwinner or Rockchip, etc and the performance is good enough for most people at an incredible price that Intel simply can't match.

    There's a reason in the early Netbook days why Intel wouldn't let Atom processors inside anything larger than 10" and 1024x768 screens, etc

    It's because Intel didn't want people being happy with Atom performance in larger computers, so if you wanted larger screens, etc you were artificially forced to pay for more processing potential than you needed.

    Intel have performance, and lately they're getting the power efficient too, but they are still a premium processor option and that's where ARM still has the advantage.

    I don't see Intel willing to drop their prices any time soon to compete with cheap Android tablets. Intel would rather create bullcrap categories like "Ultra-book" (it's still a laptop for Christ-sake !) and convincing people they NEED expensive computers that cost $800+.

    Meanwhile other ISA's like ARM and MIPS are lowering the price barrier to products with more than enough processing power and battery-life for most people.

    Intel are left to convince people they need a desktop/laptop in a world increasingly going mobile and always-connected
  • yyrkoon - Tuesday, December 25, 2012 - link

    You can even buy ICS tablets for as little as $50 is you keep an eye out.

    Personally though, I would not settle for anything less than the Nexus 7. Sometimes, peace of mind means more than money.

    Point was however, that there is more than just power /watt efficiency to consider here. Especially when enjoying those number comes at a huge price premium.

    Along the lines of what Intel can not match price wise. I am fairly confident that Intel can not even match prices with Texas Instruments in most cases. But I also believe that Intel does not need to convince buyers into thinking that desktops, and laptops are still necessary. Mainly because mostly they are( and will continue to be ). At minimum, high performance workstations, and servers will still need to exist for various applications.

    I think that x86 and ARM both will continue to be around for a very long time. Which is a good thing.
  • wsw1982 - Tuesday, December 25, 2012 - link

    So Intel cannot make atom cheaper because it don't need to pay TSMC for manufacture, don't need to pay ARM for license,do have mature 32 process than rest of the industry, do have the medfield's die area smaller than both tegra 3 and krait, and do have enough production capabilities idle for nothing.

    Desktop and server along could make Intel maintain manufacture advantage and R&D spending, how hurt is it to adopting the wasted production capability in produce the mobile chips as bonus? Anyway, the PC market will be still growing according to the all the prediction professionals, and the ATOM is quite safe to reuse the R&D spent on the core processors.

    With 100$ you can also got the netbook from Chinese manufactures which, despite the cheap feeling and bad building quality, is as responsive and useful as the netbooks from big companies. But the 80$ android tablet is nearly unusable.
  • talzara - Thursday, December 27, 2012 - link

    You do realize that Texas Instruments has exited the ARM processor business for mobile devices, right? The margins were too thin. They're still making ARMs for embedded devices, but they've given up on mobile.

    ARM is the classic disruptive innovation. It reduces prices for consumers, and cuts a swathe of destruction through industry margins. There are just too many players in ARM -- they're interchangeable enough that they have a hard time charging any kind of premium for their products.

    Nvidia has shipped tens of millions of Tegras, so much so that it now accounts for 20% of Nvidia's revenues. Great business, right? Think again. Tegra accounts for -16% of Nvidia's net income. That's not a typo -- it really is a negative number. Nvidia makes all of its money from GPUs -- gaming GPUs, consumer GPUs, and GPUs sold for massively-parallel computing. (Source: Nvidia 10-Q for Q3 of fiscal 2013 -- segment breakdown at the bottom of page 27.)

    So now we've got one major ARM vendor quitting, and another major ARM vendor bleeding cash. The ones that are doing well are the ones that don't actually care about the CPU. Qualcomm is horizontally integrated -- they make money on the LTE chipset. Apple and Samsung are vertically integrated -- they make their money on the whole device, not on the CPU.

    In such a crazy market, Intel may well prefer to sell a premium product to 5% of the market, rather than a price-competitive product to 30%.

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