The ARM vs x86 Wars Have Begun: In-Depth Power Analysis of Atom, Krait & Cortex A15
by Anand Lal Shimpi on January 4, 2013 7:32 AM EST- Posted in
- Tablets
- Intel
- Samsung
- Arm
- Cortex A15
- Smartphones
- Mobile
- SoCs
What's Next? ARM's Cortex A15
Comparing to Qualcomm's APQ8060A gives us a much better idea of how Atom fares in the modern world. Like Intel, Qualcomm appears to prioritize single threaded performance and builds its SoCs on a leading edge LP process. If this were the middle of 2012, the Qualcomm comparison is where we'd stop however this is a new year and there's a new kid in town: ARM's Cortex A15.
We've already looked at Cortex A15 performance and found it to be astounding. While Intel's 5-year old Atom core can still outperform most of the other ARM based designs on the market, the Cortex A15 easily outperforms it. But at what power cost?
To find out, we looked at a Google Nexus 10 featuring a Samsung Exynos 5250 SoC. The 5250 (aka Exynos 5 Dual) features two ARM Cortex A15s running at up to 1.7GHz, coupled with an ARM Mali-T604 GPU. The testing methodology remains identical.
Idle Power
As the Exynos 5250 isn't running Windows RT, we don't need to go through the same song and dance to wait for live tiles to stop animating. The Android home screen is static to begin with, all swings in power consumption have more to do with WiFi at this point:
At idle, the Nexus 10 platform uses more power than any of the other tablets. This shouldn't be too surprising as the display requires much more power, I don't think we can draw any conclusions about the SoC just yet. But just to be sure, let's look at power delivery to the 5250's CPU and GPU blocks themselves:
Ah the wonderful world of power gating. Despite having much more power hungry CPU cores, when they're doing nothing the ARM Cortex A15 looks no different than Atom or even Krait.
Mali-T604 looks excellent here. With virtually nothing happening on the display the GPU doesn't have a lot of work to do to begin with, I believe we're also seeing some of the benefits of Samsung's 32nm LP (HK+MG) process.
Remove WiFi from the equation and things remain fairly similar, total platform power is high thanks to a more power hungry display but at the SoC level idle power consumption is competitive. The GPU power consumption continues to be amazing, although it's possible that Samsung simply doesn't dangle as much off of the GPU power rail as the competitors.
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powerarmour - Friday, January 4, 2013 - link
So yes, finally confirming what anyone with half a brain knows, competitive ARM SoC's use less power.apinkel - Friday, January 4, 2013 - link
I'm assuming you are kidding.Atom is roughly equivalent to (dual core) Krait in power draw but has better performance.
The A15 is faster than either krait or the atom but it's power draw is too much to make it usable in a smartphone (which is I'm assuming why qualcomm had to redesign the A15 architecture for krait to make it fit into the smartphone power envelope).
The battle I still want to see is quad core krait and atom.
ImSpartacus - Friday, January 4, 2013 - link
Let me make sure I have this straight. Did Qualcomm redesign A15 to create Krait?djgandy - Friday, January 4, 2013 - link
No. Qualcomm create their own designs from scratch. They have an Instruction Set licence for ARM but they are arm "clones"apinkel - Friday, January 4, 2013 - link
Sorry, yeah, I could have worded that better.But in any case the comment now has me wondering if I'm off base in my understanding of how Qualcomm does what it does...
I've been under the impression that Qualcomm took the ARM design and tweaked it for their needs (instead of just licensing the instruction set and the full chip design top to bottom). Yeah/Nay?
fabarati - Friday, January 4, 2013 - link
Nay.They do what AMD does, they license the instruction set and create their own cpus that are compatible with the ARM ISA's (in Krait's case, the ARMv7). That's also what Apple did with their Swift cores.
Nvidia tweaked the Cortex A9 in the Tegra 2, but it was still a Cortex A9. Ditto for Samsung, Hummingbird and the Cortex A8.
designerfx - Friday, January 4, 2013 - link
do I need to remind you that the Tegra 3 has disabled cores on the RT? Using an actual android device with Tegra 3 would show better results.madmilk - Friday, January 4, 2013 - link
The disabled 5th core doesn't matter in loaded situations. During idle, screen power dominates, so it still doesn't really matter. About all you'll get is more standby time, and Atom seems to be doing fine there.designerfx - Friday, January 4, 2013 - link
The core allows a lot of different significant things - so in other words, it's extremely significant, including in high load situations as well.That has nothing to do with the Atom. You get more than standby time.
designerfx - Friday, January 4, 2013 - link
also, during idle the screen is off, usually after whatever amount of time the settings are set for. Which is easily indicated in the idle measurements. What the heck are you even talking about?