Apple's Swift: Visualized

Section by Anand Shimpi

Based on my findings on the previous pages, as well as some additional off-the-record data, this is what I believe Swift looks like at a high level:


Note that most of those blocks are just place holders as I don't know how they've changed from Cortex A9 to Swift, but the general design of the machine is likely what you see above. Swift moves from a 2-wide to a 3-wide machine at the front end. It remains a relatively small out-of-order core, but increases the number of execution ports from 3 in Cortex A9 to 5. Note the dedicated load/store port, which would help explain the tremendous gains in high bandwidth FP performance.

I asked Qualcomm for some additional details on Krait unfortunately they are being quite tight lipped about their architecture. Krait is somewhat similar to Swift in that it has a 3-wide front end, however it only has 4 ports to its 7 execution units. Qualcomm wouldn't give me specifics on what those 7 units were or how they were shared by those 4 ports. It's a shame that Intel will tell me just how big Haswell's integer and FP register files are 9 months before launch, but its competitors in the mobile SoC space are worried about sharing high level details of architectures that have been shipping for half a year.

Apple's Swift core is a wider machine than the Cortex A9, and seemingly on-par with Qualcomm's Krait. How does ARM's Cortex A15 compare? While the front end remans 3-wide, ARM claims a doubling of fetch bandwidth compared to Cortex A9. The A15 is also able to execute more types of instructions out of order, although admittedly we don't know Swift's capabilities in this regard. There's also a loop cache at the front end, something that both AMD and Intel have in their modern architectures (again, it's unclear whether or not Swift features something similar). ARM moves to three dedicated issue pools feeding 8 independent pipelines on the execution side. There are dedicated load and store pipelines, two integer ALU pipes, two FP/NEON pipes, one pipe for branches and one for all multiplies/divides. The Cortex A15 is simply a beast, and it should be more power hungry as a result. It remains to be seen how the first Cortex A15 based smartphone SoCs will compare to Swift/Krait in terms of power. ARM's big.LITTLE configuration was clearly designed to help mitigate the issues that the Cortex A15 architecture could pose from a power consumption standpoint. I suspect we haven't seen the end of NVIDIA's companion core either.

At a high level, it would appear that ARM's Cortex A15 is still a bigger machine than Swift. Swift instead feels like Apple's answer to Krait. The release cadence Apple is on right now almost guarantees that it will be a CPU generation behind in the first half of next year if everyone moves to Cortex A15 based designs.

Custom Code to Understand a Custom Core Apple's Swift: Pipeline Depth & Memory Latency
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  • grkhetan - Wednesday, October 17, 2012 - link

    Multiple display reviews conclude that the iPhone 5 has the best display in a smartphone (And much better than a Samsung Galaxy S 3)

    http://www.displaymate.com/Smartphone_ShootOut_2.h...

    http://www.anandtech.com/show/6334/iphone-5-screen...
  • rarson - Thursday, October 18, 2012 - link

    Your second link doesn't compare it to anything but the iPhone 4. Your first link ONLY compares it to the S3. Neither link supports your statement ("best display in a smartphone").
  • doobydoo - Friday, October 19, 2012 - link

    A quote from his second link:

    'To put this in perspective, in the past few years I've reviewed probably 30-40 different displays, from PC monitors to TVs to projectors. Not a single one, out of the box, can put up the Gretag Macbeth dE numbers that the iPhone can, and perhaps one projector (which listed for $20,000) can approach the grayscale and color accuracy out of the box.'
  • steven75 - Wednesday, October 17, 2012 - link

    Those pesky facts are annoying!
  • Obsoleet - Tuesday, October 16, 2012 - link

    No, it's not. There's many reasons the GS3 is the better choice based on the software and hardware, mainly that the MaxxHD only matches a 5 month old phone in hardware specs and tosses on a bigger battery as the only clear win (but you get stuck with a Motorola phone vs most people's preferred choice Samsung).
    But the killer reason is that the charger is on the left hand side.

    For many of us lefties, that is a deal breaker. As a right handed user, you don't realize this. I want the ports on the top or bottom, and I just ordered a GS3 because of this being a tipping point.

    The original Maxx had the ports on the top! Motorola is clueless.
    Never again.
  • Ckaka1993 - Thursday, December 6, 2012 - link

    Ppi does make a difference. Go see the videos of droid dna(has 440) ppi and you can make out the difference. iPhone 5 doesnt have true 720p but that doesn't matter cause it's quite close to 720p. Anyways iphone5 is behind so many smartphones at present. Nokia lumia 920 is a treat to watch with its 332 ppi pure motion hd+ display and high refresh rate, u can make out the difference. But nexus 4 is the smartphone which gives u the best worth for money at ony 350usd it is freaking awesome
  • makken - Tuesday, October 16, 2012 - link

    The Physical Comparison table lists the iPhone 5's resolution at 1136 x 960, instead of 1136 x 640. Threw me off for a second there =P
  • Brian Klug - Tuesday, October 16, 2012 - link

    Oops, fixing. There's always something in the table that needs fixing it seems :P

    -Brian
  • DukeN - Tuesday, October 16, 2012 - link

    And always favorably on the Apple side.

    Maybe you took a picture of the pixel count with the iPhone's camera...
  • Alucard291 - Tuesday, October 16, 2012 - link

    I know I love how their own benchmarks show how the battery life is worse in just about everything than the 4s and yet and yet "its better" >.>

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