Conclusion & First Impressions

Today’s Arm Client TechDay disclosures were generally quite a lot more extensive than in the last few years, especially given the number of new IP releases we’ve covered. Three new CPU microarchitectures, a new DSU/L3 cluster design, and two new SoC interconnect IPs is quite a bit more than we’re used to, and it goes to underscore just how much effort Arm is putting into updating all of the parts of its client IP.

Starting off with the CPUs, the new Cortex-X2 and Cortex-A710 cores are meant to be iterative designs compared to their predecessors, and that's certainly what they are from a performance and efficiency viewpoint. On a generational basis, Arm is promising a 10-16% improvement in IPC. However these figures are somewhat muddled by the fact we’re also comparing 4MB and 8MB L3 caches. Generally, it’s a reasonable expectation of what we’ll be seeing in 2022 devices, but it’s also hard to disambiguate and attribute the performance of the cores versus that of the new DSU-110 L3 cluster design.

Arm has also made some more lofty performance claims when it comes to actual device implementations in 2022, such as +30% peak-to-peak performance boosts on the parts of the X2 cores. Generally, given our expectations that both the next Snapdragon and the next Exynos flagships will come in a similar Samsung foundry process node with smaller improvements, I’m very doubtful we’ll be seeing such larger generational improvements in practice, unless somehow MediaTek surprises us with a flagship X2 SoC made out at TSMC.

While the X2 and A710 aren’t all that groundbreaking, we have to note that the move towards Armv9 brings a lot of new architectural features that would otherwise eat into the expected yearly performance or efficiency improvements. The move to the new ISA baseline has been a long time coming and I’m curious to see what it will enable in terms of media applications (SVE) or AI (new ML instructions).

This is also the fourth and last iteration of Arm’s Austin core family, so hopefully next year’s new Sophia family will see larger generational leaps. Arm admits that we’re nearing diminishing returns and it’s certainly not at the same break-neck pace it was moving a few years ago, but there’s still a lot which can be done.

Today we also saw the unveiling of a brand-new little core in the form of the Cortex-A510. A new clean-sheet design from the Cambridge team, it’s certainly using an innovative approach given its “merged core” design, sharing the L2 cache hierarchy and the FP/SIMD back-end amongst two otherwise full featured cores. The performance and IPC gains are claimed to be quite large at +35-50%, however it seems that this generation hasn’t improved the efficiency curve all that much. It’s still a much better design and will have effective benefits for power efficiency in real-world workloads due to how workloads interact between the little and larger cores, but leaves us with a feeling that it doesn’t provide a knock-out convincing jump we had expected after 4 years. The silver lining here is that Arm is promising further generational improvements in performance and power with subsequent iterations, so we won’t be left with the current state of affairs the same way we saw the Cortex-A55 stagnate.

One of the more key points I saw Arm put their focus on was the new possibilities in larger form-factor devices beyond mobile. The new DSU-110 now supports up to 8 Cortex-X2 cores, a theoretical setup that would pretty much blow away the current Cortex-A76 based Arm laptop SoCs such as the Snapdragon 8cx family. The new cluster design allows for large L3 caches of up to 16MB, and while I don’t know if we’ll see the new interconnect IPs used by the larger vendors, it surely also makes a big argument for larger performance designs. The catch is that if Qualcomm were to adopt and make such a design, it would seemingly be short-lived given their recent Nuvia acquisition and intent on using custom cores. Otherwise, because of a lack of Mali Windows drivers, this really only leaves space for a theoretical Samsung laptop SoC with AMD RDNA GPU, but such a SoC could nonetheless be very successful.

Overall, this year’s CPU and system IP announcements from Arm are extremely solid new IP offerings, really laying down a new foundation, both architecturally with Armv9, and microarchitecturally thanks to elements such as the new DSU and the new little core CPUs. We’re looking forward to the new 2022 SoCs and products that will be powered by the new Arm IP.

A new CI-700 Coherent Interconnect & NI-700 NoC For SoCs
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  • jeremyshaw - Tuesday, May 25, 2021 - link

    Something I'm not quite catching with the DSU, does it allow for different configurations that we've already seen? Something like the 8xA78C we saw announced a while back? Reply
  • jeremyshaw - Tuesday, May 25, 2021 - link

    *than, sorry Reply
  • SarahKerrigan - Tuesday, May 25, 2021 - link

    They show 8x X2 configs, so I'd be shocked if 8xA710 was not also on the menu. Reply
  • igor velky - Tuesday, May 25, 2021 - link

    first two slides on page 5 will give you answer,

    both slides show cpu cores inside one cpu cluster
    first slide shows different cores,
    second shows only one type of core in cpu cluster

    on page 6 because of bad formatting there are two slides looking like one picture

    so second slide, bottom half of first picture
    shows you that you can put max 8 cpu clusters to one chip.

    so you can have
    max 8 cpu cores per cpu cluster
    times
    8 cpu clusters per one chip.

    you choose cores, you choose how many cores, you choose which type of cores, you choose how many memory channels, you choose how many and what type of additional accelerators you put inside chip...

    because youre apple, samsung, qualcomm...
    and you choose this things and let someone to "etch it" into silicon.
    and you then sell it.
    Reply
  • melgross - Tuesday, May 25, 2021 - link

    Well, Apple doesn’t “choose” cores, they design them from scratch. Reply
  • Linustechtips12#6900xt - Wednesday, May 26, 2021 - link

    ehhh, they get the IP for cores like the x1 or a76 then they tweak them either a lot or a little and create their current "firestorm/Icestorm" cores Reply
  • michael2k - Wednesday, May 26, 2021 - link

    Sure, they tweak them a lot, just like I tweaked your post a lot to make my own. The A13 released in 2019 was an 8 wide CPU; in comparison the state of the art A76 at the time was only a 4 wide CPU. That’s a pretty big deal.

    The X1 has an 8 wide dispatch, meaning it can issue 8 Mops per cycle but only decode 5 instructions per cycle. This is 2 years after Apple released the A13 which was 8 wide dispatch and decode. If you look at Anandtech’s A14 article you see that Apple has made the Icestorm cores roughly equivalent to an A76 since it is a 3 wide out of order design.

    You can read more here:
    https://www.anandtech.com/show/16226/apple-silicon...
    Reply
  • mattbe - Wednesday, May 26, 2021 - link

    This is complete BS. They license the ISA from ARM. They DO NOT USE OR TWEAK cores like the X1 and A76 to create their firestorm/ice storm cores. These are information that can easily be verified so it's pretty ignorant for you to make those claims. Reply
  • FunBunny2 - Wednesday, May 26, 2021 - link

    " They DO NOT USE OR TWEAK cores"

    near as I can tell, most 'innovation' in cpu design/engineering has been, for years, throwing ever expanding transistor budgets (can we expect that to continue?) at register width, path width, buffer/cache width and number, pulling off-chip function on-chip. and the like. if Apple should ever publish the full spec of one of these chips, will we see that they've done anything more 'innovative' than Bigger, Wider, More?

    all of the 'innovation' cited by michael2k fits that bill.
    Reply
  • mode_13h - Thursday, May 27, 2021 - link

    > if Apple should ever publish the full spec of one of these chips,
    > will we see that they've done anything more 'innovative' than Bigger, Wider, More?

    You don't get perf/W numbers like Apple's by simply doing "bigger, wider, more".

    There's information out there about some of their tricks, if you're willing to look for it. But I understand that it takes work and why do that, when you're perfectly content in your belief that there's nothing new under the sun?
    Reply

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