The Snapdragon 865 SoC: Beating Expectations

We’ve covered the Snapdragon 865 extensively over the last few months, and more recently did a performance preview of the chip on the Galaxy S20 Ultra:

It’s safe to say that Qualcomm managed to beat our expectations in terms of power efficiency improvements. Which is something we’ll go over in more detail in this piece as well.

At the heart of the Snapdragon 865 we find Arm’s newest Cortex-A77 CPU cores. The new microarchitecture is said to bring a 20-25% IPC improvement over its predecessors, and that’s where the new SoC derives most of its performance improvements from, as the clock frequencies of the cores are identical to that of last year’s Snapdragon 855.


Snapdragon 865 CPU Topology

One aspect where Qualcomm did improve the design is in doubling the shared L3 cache of the CPU cluster, going from 2MB to 4MB. Not only does this further improve the performance of the CPUs by allowing for more data to be cached on-chip, but Qualcomm has explained that one of the primary reasons for this was to also improve power efficiency of the SoC by reducing how often the SoC has to access the DRAM, which is a relatively power-expensive operation.

The chip still has a 3MB system level cache that serves the various IP blocks on the SoC – it’s again meant to not only improve performance but also improve power efficiency as it avoids external memory accesses. The memory subsystem here is smart and detects when to bypass this cache when there’s latency-sensitive workloads, and in general we’ll see some massive memory subsystem improvements on the part of the Snapdragon 865 in a later dedicated section.

All the CPUs being in the same cluster and cache hierarchy means that the core-to-core latencies are relatively uniform, only differing based on their frequencies and lower level cache access latencies. It’s not too much of an exciting metric here, but it’s important context to have as we’ll consider the Exynos 990’s CPU topology in just a bit.

Again, we’ve covered the Snapdragon 865 quite extensively in the above linked articles so I recommend reading them again for other details on other parts of the new chip, such as the new ISP, DSP, and GPU details. However, one aspect that’s very defining for the flagship Qualcomm chipset this year is that the company is separating the modem from the SoC – essentially making the SoC just an application processor for this generation.

The external nature of the X55 modem has a few implications: first of all, there’s an additional component on the motherboard which vendors will have to make space for, which means additional cost. Secondly, there’s the big question of how power efficiency will be affected by the external modem. We’ve seen Apple devices perform excellently over the years while never having an integrated modem, and I feel like the Snapdragon 865 and X55 also fall into this classification, as I haven’t seen any major differences in efficiency due to the external nature of the modem.

Design, Continued: An Ultra Mega Phone The Exynos 990 SoC: Last of Custom CPUs
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  • Reflex78 - Friday, April 3, 2020 - link

    I live in Europe, I like Samsung and have S9 at the moment.
    But I will never pay +1000€ for lower quality Exynos S20 version in Europe!
    This is a big mistake from the company management to allow such a difference between this 2 variants at the same price!
    And I just read that they have chosen to sell Snapdragon version even for their home country:
    https://www.phonearena.com/news/Samsung-chip-divis...
    Reply
  • twtech - Friday, April 3, 2020 - link

    The edge design of Samsung's more recent releases is just not good. There are no cases that can both properly protect the screen, and avoid blocking any of it. My older phones typically lasted for years without any significant damage. These new ones are one slip of the hand away from being garbage fodder. Reply
  • FunBunny2 - Friday, April 3, 2020 - link

    "These new ones are one slip of the hand away from being garbage fodder."

    rube!! :) it's a feature, not a bug. going back to Lotus/MS conflict: "DOS ain't done til 1-2-3 won't run."
    Reply
  • Harysviewty - Friday, April 3, 2020 - link

    Totally wrong calculation. It's 7.1mp when you crop 3x3. It's only possible to do full 12mp resolution with the help of Super resolution algorithm, which adds up to 75% more detail to 'normal bayer' setup Reply
  • Andrei Frumusanu - Friday, April 3, 2020 - link

    I don't know what you're talking about. The sensor is 108MP at 12000 x 9000. 3x3 binning results in 4000 x 3000, which is 12MP. Reply
  • krazyfrog - Friday, April 3, 2020 - link

    The 3x3 binning only happens on the 108MP sensor, not on the 64MP sensor. Reply
  • s.yu - Saturday, April 4, 2020 - link

    You said "crop 3x3" which confuses people, usually we just say 3x crop, but yes, the digital zoom doesn't provide native 12MP in any sense at 3x. Reply
  • JDSP - Friday, April 3, 2020 - link

    Image links on the iPhone are wrong, Wide links to zoom and night sight links to normal Reply
  • Andrei Frumusanu - Friday, April 3, 2020 - link

    Corrected that, thanks. There's probably a few other link issues there I'll keep an eye out for that. Reply
  • Quantumz0d - Friday, April 3, 2020 - link

    Great analysis, will go through it slowly but looking at that Exynos 990, Seriously WTF is that. Higher power consumption, lower GPU performance, higher throttling. Very unfortunate. And losing to that copycat Chinese Huawei Kirin trash (EMUI garbage with LZ Play backdoor, Read only EROFS Filesystem and Google copying that into Pixel 4 and the proprietary garbage NMSDslot no 3.5mm jack, No Play Store, lies and deception) Samsung should be ashamed of themselves removing all their genius whatever PR ads for milking customers and offering mediocrity.

    The only good part for Exynos is unlockable bootloader. Since SD versions in US are locked as hell and useless for customization esp how they depreciated the SpO2 sensor in this phone HW and from SW side also in S10 and previous phones to promote bullshit Smartwatches.

    This phone sucks bad, their S10 has better features and looks better as well on top this phone camera sucks, no 3.5mm jack and ugliest design ever with insane price tag on top, LG's V60 is looking very good in comparison from Camera to Audio and other features/specs plus price vs this phone or even that Chinese OP8 Pro (despite lacking SD slot and 3.5mm jack as at-least it is cheaper and has hassle free Bootloader unlock), since Samsung dropping HW feature set which defines the all in one phones from Samsung they want greed and money from that shitty Buds and other garbage.

    S10+ Exynos is a better choice all rounder as it has BL unlock as well. On top I'd like to mention how DJ Koh also was removed from the Samsung mobile CEO office, I presume it also played an important role in S.LSI even if independent and the financial results of the conglomerate, esp how it impacted the design philosophy for sure as Note 10 provided a platform for removing features and cost cutting similar aspect in S20 a bit more worse.

    On the Foundry aspects, TSMC 7NP is not EUV and Samsung 7nm LPP is EUV since N7+ is the EUV one. Not sure 20% to 30% is valid ? I do not know since the uArch is garbage doesn't mean that the node is trash, esp last rumor was Ampere would be on Samsung node with EUV and Nvidia wouldn't afford a stupid decision tbh, and a big shame is S.LSI getting hacked. I think the PR marketing team and the budgets ruined them or such, we may never know. Shame indeed.
    Reply

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