Performance: Atom vs. ARM's Cortex A15

In our iPhone 5 review I included this crude diagram comparing the high level micro-architecture layouts of the current crop of mobile CPU cores. While most of the cores looked fairly similar, the one to really stand out is ARM's Cortex A15. A three issue, OoO core, the Cortex A15 was designed to put ARM in a completely new performance category.


For 2013, the Cortex A15 is expected to be the ARM CPU core of choice for the next wave of smartphone and tablet SoCs. NVIDIA's Wayne should integrate multiple Cortex A15s as well as competing solutions from Samsung and TI. Samsung's Exynos 5 Dual, found in the new Chromebook, integrates two ARM Cortex A15 cores running at 1.7GHz. As our first experience with a Cortex A15, I wanted to get a good idea for how it would compare to Intel's Atom. And now me comparing to the older Chromebook 500 makes sense. The Atom N570 in the older Chromebook is the closest approximation we have to the currently shipping Atom based mobile SoCs. There are a number of enhancements to the newer chips (particularly when it comes to power consumption), but the base core is very similar. It's clear that the Sandy Bridge Celeron based Chromebook is faster than this new Cortex A15 design, but how about the old dual-core Atom model?

As Chrome OS is built around the Chrome browser, our tests had to be largely JavaScript based unfortunately. The good news is that even given the nature of the benchmarks, we're able to get a good feel for performance between the two SoC platforms. Both systems were running the latest version of Chrome OS at the time of publishing.

Samsung Chromebook Performance Comparison
  SunSpider 0.9.1 BrowserMark RIABench Focus Tests Kraken
Atom N570 1.66GHz 1034.3 ms 152780 1968 ms 14229.5 ms
Exynos 5 Dual 1.7GHz 690.5 ms 217031 1192 ms 9733.2 ms

The Cortex A15 is fast. Across the board we're seeing a 40 - 65% increase in performance over a dual-core Atom. Although it's not clear how performance will be impacted as companies work to stick Cortex A15 based SoCs in smartphones with tighter power/thermal budgets, in notebooks (and perhaps even tablets) the Cortex A15 looks capable of delivering a good 1 - 2 generation boost over Intel's original Atom core.

The IE10 browser tests tend to agree with our JavaScript performance tests, although the CSS Maze Solver benchmark shows a huge advantage for ARM over Intel's Atom here.

Samsung Chromebook Performance Comparison
  IE10 Bubbles Test IE10 Fishbowl IE10 Maze Solver
Atom N570 1.66GHz 11 fps 5 fps 45 seconds
Exynos 5 Dual 1.7GHz 17 fps 8 fps 17 seconds

GPU performance is an even bigger advantage for the Exynos 5 Dual over Intel's old Atom N570 (GMA-3150 GPU). I ran three different webGL tests, each of which showed just how bad the old Atom GPU core was.

Samsung Chromebook GPU Performance Comparison
  WebGL Solar System WebGL Cubes (500) WebGL Aquarium (50)
Atom N570 1.66GHz 2 fps 10 fps 2 fps
Exynos 5 Dual 1.7GHz 22 fps 28 fps 38 fps

This comparison isn't really all that fair as the newer Atom cores use Imagination GPUs, although even then they are using relatively underpowered solutions compared to what Samsung is shipping on the Exynos 5 Dual.

The more relevant conclusions here apply to the CPU comparison. Next year Intel is expected to introduce its first new Atom core since the platform's introduction five years ago. The new architecture will bring an Out of Order execution core as well as a tangible performance increase. The question is whether or not this will be enough to fend off advances from Cortex A15 based designs.


The new Chromebook (left) vs. the old Atom based Chromebook (right)

In our Surface review I looked at Clovertrail Windows 8 tablet performance and put it a good 40%+ faster than NVIDIA's Tegra 3. If ARM's Cortex A15 is able to outperform Clovertrail by a similar margin, it could make the next generation of Windows RT tablets even more attractive. Keep in mind that we're looking at an older Atom platform here and not Clovertrail, so the performance deltas could shrink a bit.

User Experience & Usability Battery Life & Power Analysis
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  • wumpus - Wednesday, October 31, 2012 - link

    I would assume that the real issue is if you can wipe chromeOS and replace with the linux of your choice. By the security choices you list, I wouldn't be using any type of windows box. From the comments below, there doesn't appear to be a "plug a USB stick in and hit a button" linux disto yet. Reply
  • jeffkro - Wednesday, October 31, 2012 - link

    Look into ixquick if you are worried about search privacy. Reply
  • jeffkro - Wednesday, October 31, 2012 - link

    "I'm not sure, but I think there's no choice for editing text apart from Google Docs?"

    If you are really tied to MS office you can use MS's cloud based office suite.
    Reply
  • jjj - Wednesday, October 31, 2012 - link

    Nice perf numbers.On power consumption both the software and the hardware are a lot different form a phone so maybe it's not as bad as you think.
    Now all we need is quad A15 :D (might be doable in tablets/notebooks with bigLITTLE or Nvidia's 4+1 even on 28nm)
    Reply
  • Roland00Address - Wednesday, October 31, 2012 - link

    It will be 4 A15 cores plus a low power companion core. Who knows when it will be actually in devices.

    I have not heard any announcements for quad core A15 from other sources (such as Samsung) that said it is going to happen sometime even if it has not been announced.
    Reply
  • Jorange - Wednesday, October 31, 2012 - link

    Excellent I've been waiting for this review. Exynos 5250 does seem a power hungry chap, which kinda destroys my hopes for a quad-core 5450 / Mali T658 in the next Galaxy phone, unless Samsung move to a new node. There is mention of 28nm process on Samsung's foundry site, combined with Big.little maybe my dreams are alive.

    Anand, any news when Samsung will adopt a new process node, and will it be 28nm or 22nm?

    Work is already underway to port Ubuntu to it:)

    http://www.omgubuntu.co.uk/2012/10/ubuntu-12-04-up...
    Reply
  • amdwilliam1985 - Wednesday, October 31, 2012 - link

    I share your excitement, I have SGS3 and I'm so looking forward to SGS4 and what it can bring to the table. Hopefully some sort of big.LITTLE design to lower the power draw, also there is a trend of bigger battery, hopefully the trend continues without much increasing in the physical size. Reply
  • Krysto - Thursday, November 01, 2012 - link

    Why? Samsung will do it just like Nvidia with Tegra 4, and put 1 or 2 Cortex A7 chips next to the A15's, which will handle 80% of the tasks. Reply
  • Aenean144 - Thursday, November 01, 2012 - link

    I'm curious how big.LITTLE is going to work in practice. The auto switching between discrete graphics and integrated graphics on laptops may give us a clue on how well it works.

    Hitting 9 W peak at 1.7 GHz? That's Haswell territory, and I'd surmise Haswell will crush any ARM, even the 64 bit ones in 2014, with a 10 W TDP envelope.

    Secondarily, either Samsung is binning some low power parts for the Nexus 10 and prospective smartphones, or they have to downclock. The big question would be how much would they have to downclock.

    On to the Nexus 10 analysis.
    Reply
  • Kevin G - Wednesday, October 31, 2012 - link

    Very respectable performance from the Cortex A15. It'll be interesting to see how it'll fair in a smart phone but the bar has been set. Reply

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