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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  • sprockkets - Friday, January 8, 2010 - link

    It's a loser called DLeRium who thinks I don't know the diff btw x86 and PPC or ARM.

    Perhaps he doesn't know I compile code from scratch all the time for Linux and most of that code easily compiles on multiple archs. That doesn't mean its automatic to go from x86 to ARM, but it isn't an insurmountable hurdle either.
  • sprockkets - Friday, January 8, 2010 - link

    Hasn't stopped Doom or Quake 3 from arriving on the iphone, has it?
  • SilthDraeth - Friday, January 8, 2010 - link

    WoW runs in OpenGL as well.
  • rennya - Friday, January 8, 2010 - link

    And that's why Quake 3 is used in the demo. They are easily portable, unlike WoW or Sims games.

    Now if we have WoW or Sims games on iPhone you may have a point.
  • sprockkets - Friday, January 8, 2010 - link

    WoW is a ways off perhaps, but again, my original point was it is on OSX, which doesn't have DirectX. The previous poster was going on about x86 vs. ARM limitations.

    UT2004 had DirectX and OpenGL versions.

    For that matter, I believe the real question is, why would you want to game on a 3.7-5 inch screen? Even if you used video out, you would then end up hooking up some form of controller, and you'd be back to square one where you were with a computer.

    But hey, surprise me. Boxee has the Tegra2 in it. Linux is a common denominator in phones and with ARM and OpenGL ES.
  • Genx87 - Friday, January 8, 2010 - link

    How big at Nintendo DS screens? Those seem to sell at a clip higher than the stand alone consoles.
  • puffpio - Thursday, January 7, 2010 - link

    My next smartphone better have this...as well as my future HTPC/NASbox/fileserver/DNLA server/torrentbox all in one device thingy
  • puffpio - Thursday, January 7, 2010 - link

    and said smartphone needs hdmi out to drive a 1080p display
  • Goty - Thursday, January 7, 2010 - link

    I can find solutions that perform "well enough" until NVIDIA decides to stop being one of the most underhanded and disrespectful companies I can think of.
  • sprockkets - Thursday, January 7, 2010 - link

    " 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"

    LOL, now we are basing our smartphone purchases like we did 10 years ago with computers?

    OK, let's wait for Tegra2 so we can watch an 8-12GB pirated 1920x800 HDx264 hi profile movie on an 800x480 screen with headphones or even worse, a 2 inch tinny speaker even though it has DTS audio. LOL.

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