Atom vs. Cortex A9

With Atom Intel adopted an in-order architecture to save power. With Cortex A9, ARM went out of order to improve performance. Despite the fundamental difference, Atom and ARM's Cortex A9 appear similar from a high level.

Atom has two instruction decoders at the front end, as does the A9. The dual decoders feed an instruction queue that can dispatch out of order:


Intel's Atom Architecture

Both architectures appear to have a unified instruction queue that feed four dispatch ports. Atom has two ports that feed AGUs and/or ALUs, and two ports for the FPU (one for SSE and one for FP ops). A9 has two ALU ports, one FPU/NEON port and one AGU port.


Single-core ARM Cortex A9

Atom's advantage here is Hyper Threading as two threads get to share its execution resources simultaneously. Cortex A9's advantage is in a shallower pipeline and out of order execution. Both promote higher IPC but go about it in very different ways. If ARM can get clock speeds high enough they may actually have a higher performance option.

Final Words

Honestly, Tegra 2 is one of the most exciting things I've seen at CES - but it's mostly because of its dual Cortex A9 cores. While I'm excited about improving 3D graphics performance on tablets and smartphones, I believe general purpose performance needs improvement. ARM's Cortex A9 provides that improvement.

The days of me pestering smartphone vendors to drop ARM11 and embrace Cortex A8 are over. It's all about A9 now. NVIDIA delivers one solution with Tegra 2, but TI's OMAP 4 will also ship with a pair of A9s.

The big unknown continues to be actual, comparable power consumption. We're also lacking measurable graphics performance compared to the PowerVR SGX cores (particularly the SGX 540).

If NVIDIA is to be believed, then Tegra 2 is the SoC to get. I suspect that's being somewhat optimistic. But rest assured that if you're buying a smartphone in 2010, it's not Snapdragon that you want but something based on Cortex A9. NVIDIA is a viable option there and we'll have to wait until Mobile World Congress next month to see if there are any promising designs based on Tegra 2.

And just in case I wasn't clear earlier, we will see the first Tegra based Android phone in 2010. I just hope it's good.

ARM Cortex A9: What I'm Excited About
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  • strikeback03 - Friday, January 8, 2010 - link

    That would be a gigantic phone. I'd personally like to see something with this kind of processing power (minus the video acceleration) and small enough to use something like a 2.5-3" screen
  • yyrkoon - Thursday, January 7, 2010 - link

    on a smart phone, or a mp3 player . . . hmm am I missing something here ? Is this absolutely necessary ? Personally, I don't think so.

    Also comparing ARM with an Atom processor is like comparing apples to oranges isn't it ? One is x86, the other is not.

    Personally, I would be more interested in seeing how viable nVidias Tegra 2 would be used in other SoC embedded applications, or if nVidia will make derivatives that are more suitable for other than smartphone / mp3 player applications. Based just on the ARM technology, I would have to say these are going to be well suited for any low power application provided they perform well.
  • FaaR - Thursday, January 7, 2010 - link

    1080P decode support on a thing like this is... Well, virtually useless, really.

    When it's been shown that most people can't see the difference between blu-ray video and regular 'ol DVDs even on big-screen TVs, and the vast majority of people just don't see the point of HD video, then what the hell are we going to use this thing for? Watch BR rips on a 3" LCD screen, no I don't think so.

    Plug it in to your big screen TV in the living room? Please. Don't you have a stationary player for that?

    I've no idea who exactly this product is intended for.

    And the dual A9 cores, well, I'm sure they're great - compared to whatever came before them anyway, but dual A9 cores, quad A9 cores or a quadrillion A9 cores doesn't really matter as long as they don't run any really useful software and THEY DON'T. As long as a portable isn't x86 compatible it'll never be more than a toy. Yeah sure, you can "do stuff" with an Iphone or whatever, but it's still just toy apps and it will stay that way until x86 becomes a realistic alternative in the mobile marketspace. Atom is a joke right now, it's slow AND power hungry. Maybe in another 5 years, who knows...
  • Visual - Friday, January 8, 2010 - link

    it is nice if the device can decode the video in real time, even if it doesn't show it in its full resolution. then you don't need to re-encode stuff specially for the device, if size isn't a constraint - like if you are watching it from a network share.

    but the main advantage of tegra 2 isn't just some stupid video decode. its all-round general purpose cpu performance, and 3d acceleration, at very low power usage. the modular design allows it to use as little power as the current usage pattern of the device requires so it will make fantastic handheld game console/phone/media player hybrids

    and you whining that there aren't useful apps is just stupid. x86 isn't the world, you know - properly developed apps can be ported to anything, and once the platform is in people's hands, the apps will be too.
  • FlyTexas - Friday, January 8, 2010 - link

    Huh?

    What are you smoking???

    If you can't tell the very obvious difference between Blu-Ray and DVD video on a large 1080P LCD, then you're blind...

    None of that makes your other point invalid, 1080P isn't needed for a 4" screen, but it is nice that it can do it.
  • GeorgeH - Thursday, January 7, 2010 - link

    Looking at that reference board it doesn't appear that it would be all that difficult to make a mini-ITX Atom alternative. You'd have to run Linux on it, but for an HTPC, NAS, or other low power single-purpose application spending $100+ on a fully featured Windows license is a little bit silly anyway.

    If it is faster than Atom (and better at HTPC-centric video tasks) and can be had for much less than an i3 system (especially if i3 can't be passively cooled) I'd think NVIDIA would be jumping at the chance to show Intel up a bit. Even if the actual marketshare and economic gains were minimal, it seems to me that the "mindshare" gains could be huge.
  • yyrkoon - Thursday, January 7, 2010 - link

    Personally, I do not see it happening. There is a reason why companies like SGI moved from RISC to x86 hardware. However, with that said ther is simply no reason why these SoCs could not be used in an external NAS / SAN system with the right software to back it up. x86 has the advantage of running desktop classed Windows, even if only for gaming, which is a larger market than most think.

    Still, as a novice embedded designer, I see lots of potential in Tegra 2, but a lot of it would be unnecessary for my, and possibly others purposes. Smart phone, and MP3 players, sure, but not for a lot of other things. Perhaps if the graphics core were CUDA compliant and offered good number crunching performance . . .
  • yyrkoon - Thursday, January 7, 2010 - link

    Personally, I do not see it happening. There is a reason why companies like SGI moved from RISC to x86 hardware. However, with that said ther is simply no reason why these SoCs could not be used in an external NAS / SAN system with the right software to back it up. x86 has the advantage of running desktop classed Windows, even if only for gaming, which is a larger market than most think.

    Still, as a novice embedded designer, I see lots of potential in Tegra 2, but a lot of it would be unnecessary for my, and possibly others purposes. Smart phone, and MP3 players, sure, but not for a lot of other things. Perhaps if the graphics core were CUDA compliant and offered good number crunching performance . . .
  • altarity - Thursday, January 7, 2010 - link

    LOL... I seriously didn't know this when I posted earlier:

    http://blog.boxee.tv/2010/01/07/boxee-box-internal...">http://blog.boxee.tv/2010/01/07/boxee-box-internal...
  • sprockkets - Thursday, January 7, 2010 - link

    Now if only it wasn't shaped so weird...

    Is that really the final look?

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