Memory Subsystems Compared

On the memory subsystem side, there’s quite a few big changes for both the Snapdragon 865 as well as the Exynos 990, as these are the first commercial SoCs on the market using LPDDR5. Qualcomm especially is said to have made huge progress in its memory subsystem, and we’re now able to verify the initially promissing results we saw on the QRD865 back in December with a production device.

And indeed, the news keeps on getting better for Qualcomm, as the new Galaxy S20 showcases even better memory results than we had measured on the reference device. The improvements over the Snapdragon 855 are just enormous and Qualcomm not only manages to catch up but very much now is able to beat the Exynos chips in terms of memory subsystem performance.

Arm very famously quotes that an improvement of 5ns in memory latency corresponds to an increase of around 1% in performance. And if that’s the case, Qualcomm will have had a ~12% improvement in CPU performance just by virtue of the new memory controller and SoC memory subsystem design. Our structural estimate in the memory latency falls in around 106 vs 124ns – most of the improvement seems to be due to how Qualcomm is now handling accesses to the DRAM chips themselves, previously attributing the bad latencies on the Snapdragon 855 due to power management mechanisms.

Samsung’s Exynos 990 also improves in memory latency compared to the Exynos 9820, but by a smaller margin than what the Snapdragon 865 was able to achieve. All latency patterns here are still clearly worse than the Qualcomm chip, and there’s some oddities in the results. Let’s zoom in into a logarithmic graph:

 

Comparing the Exynos 990 results vs the Exynos 9820, it’s now quite visible that the L2 cache has increased dramatically in size, similar to what we’ve described on the previous page, corresponding to the doubling of the available cache to a core from 1MB to 2MB. Samsung’s cores still have some advantages, for example they’re still on a 3-cycle L1 latency design whereas the Arm cores make due with 4-cycle accesses, however in other regards, the design just falls apart.

The TLB issues that we had described last year in the M4 are still very much present in the M5 core, which results in some absurd results such as random accesses over a 2MB region being actually faster than at 1MB. Cache-line accesses with TLB miss penalties now actually have lower access latencies in the L3 than in the L2 regions, and I have no idea what’s happening in the 16-64MB region in that test as it behaves worse than the 9820.

Examining the A76 cores of the Exynos 990, we see a much cleaner set of results more akin to what you’d expect to see from a CPU. Here we also see the 2MB SLC cache hierarchy in the 1-3MB region, meaning the Arm core cluster does have access to this cache, with the M5 cores bypassing it for better latency. Last year I had noted that the A76’s prefetchers had seen some massive improvements, and this is again evident here in the result sets of the two CPUs on the same chip as the middle cores actually handle some access patterns better than the M5 cores.

Samsung has had large issues with its memory subsystem ever since the M3 design, and unfortunately it seems they never addressed them, even with the more recent M5 core.

The Snapdragon 865 here is quite straightforward. The biggest difference to the 855, besides the improved DRAM latency, is the doubling of the L3 from 2 to 4MB which is also immediately visible. It still pales in comparison to the Apple A13’s cache hierarchy, but we do hope that the Arm vendors will be able to catch up in the next few years.

The Exynos 990 SoC: Last of Custom CPUs SPEC2006: Worst Disparity Yet
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  • Andrei Frumusanu - Friday, April 3, 2020 - link

    Probably one of the reasons Samsung still continues to sell the S10 series. They're really excellent value right now, and you're not missing out on too much. Reply
  • cha0z_ - Monday, April 6, 2020 - link

    You are literally getting just one more year of software support going for s10 series... samsung software support policy is abysmal with less than two years of real support and from there just security. I got both iphone 11 pro max and exynos note 9, if I put aside the cr*ppy 9810 - it will not receive even the oneUI 2.1 as an update, while samsung will soon release it for s10 line. Enough said, note 9 is year and a half old.

    How can you recommend someone 1000 euro or 1400 euro phone if it will be supported for 1.5 years and from there 1.5 more security updates next to apple with 5 years FULL support with major, minor, day one, betas + security update for old iphones like 4s and 5 (2011 and 2012 respectably)?
    Reply
  • goatfajitas - Monday, April 6, 2020 - link

    You do realize the phone doesn't stop working when it doesn't get an OS update right? TBH, neither Android or IOS has added a whole lot in the past few years, its just a yearly cadence of very minor updates and not getting them means almost zero in actual use. Reply
  • Featherinmycap - Monday, April 6, 2020 - link

    I think there have been a lot of added features to IOS in the last 3 years that I use a great deal. Not saying that Android didnt already have some of these features, but for IOS users we got with IOS 11; a file manager (finally), Messages sync with iCloud, screen recording, useful improvements to Siri and ApplePay. IOS12; lots of performance improvements (lots), Screentime, Shortcuts (scripting), CarPlay, Animoji Memoji, Tracking prevention, IOS13; Single Sign on, external storage, Dark Mode, better support for keyboards, trackpads/mice, etc. Reply
  • Famorcan007 - Tuesday, April 7, 2020 - link

    I think it's because Android mostly has offered those features(file manager,screen recording, external storage,support for mice etc.) since way back compared to iOS' slow but steady trickle of features that's why iOS users feel every OS update is huge and significant. I'm using a Note 4(my backup device) right now to comment which doesn't feel too crippled compared to my Android 9 P20 pro. Reply
  • cha0z_ - Tuesday, April 7, 2020 - link

    Let's not find an excuse - software support is software support. Security is security - some of us keep all their personal info on their device (most of us) + bank accounts and whatnot, risking compromise on your phone is not that innocent compared to what was like back in the days. IOS adds rapidly more features for sure compared to android that recently starts to look more and more like IOS (and I personally totally don't like that), but still added some good stuff under the hood and some new features.

    It's not serious to sell 1400 euro phone that is supported for one year and a half. I own exynos note 9 - it's 1.5 years old and already samsung dropped the support, s10 line received oneUI 2.1, note 9 will not. How is that for my 1000 euro phone + double served with that cr*ppy exynos 9810 in it. Now it's in my GF and I am rolling iphone 11 pro max. I prefer android and love oneUI, but I am tired to be a second hand customer.
    Reply
  • s.yu - Tuesday, April 7, 2020 - link

    Don't know what you're talking about. My Note8 just got another update days ago, one that I preferred not to have because each update comes with a risk of bricking the device while potential changes to the UI are not always welcome either. I also got it ~30% off retail a few months after release, such has always been the state of Samsung, at least for S and Note.
    I'm no longer buying Samsung but the main reason is lack of the 3.5mm port, if I have to name another then it's between the questionable choice of telephoto in the smaller variants or the oversized device with a mediocre battery(I regard 5000mah to be mediocre for the size). I still do like the UI but I'm willing to look around.
    Reply
  • Psyside - Tuesday, April 7, 2020 - link

    "It's not serious to sell 1400 euro phone that is supported for one year and a half. I own exynos note 9 - it's 1.5 years old and already samsung dropped the support, s10 line received oneUI 2.1, note 9 will not. How is that for my 1000 euro phone"

    Very easy, with those "very old software features" Samsung can do what MAC can't, and don't get me start it on the utter crap IOS.

    Also don't spin it, Samsung offer 4 (four) years of security updates, so do your research before you type something.
    Reply
  • cha0z_ - Wednesday, April 8, 2020 - link

    fanboy. Security update hahahahah iphone 4s and 5 still receives security updates - 9 years old phone for 4s. What you will say now?
    iphone receive FULL support with MAJOR ios versions, updates, minor updates, BETA versions, DAY ONE as their newest and most expensive phone - for 5-6 years and you are talking about 4 years of security updates roflmao. Samsung released note 9 with android 8 when android 9 was already released from more than a months. Oooo, it's enough time, because you can dev your skin and features on top of the dev previews, especially the later ones that are closer to final (for the more tricky/deeply integrated code) - so no excuse for what they did. Basically they gave me one major update - android 10 as android 9 should had been on the note 9 from the start. Even if we count 2, how is that next to 5-6 versions of ios?

    And before you talk some more fanboy bs that never used recent years iphones - ios brings a lot more in every new versions (adding features that was missing for no reason, like external USB flash support, file browser for the files on the phone, etc) while android 10 brings you what? More lockdown ios style, iphones gestures and pixel device that is a cheap iphone wannabe.

    Because of people like you samsung don't want to change their software support policy. Why should they? It costs money or now you will start with the argument how the phone hardware is not supporting oneUI 2.1 (for the note 9 that is 1.5 years old, but will not receive it most likely ;) ). Or maybe android 11 will be too much for the phone, right? :D

    Also I agree - my note 9 can do more than my iphone 11 pro max, but everything that the phones do both (and that's 99.9% of what you will end up using constantly) - the iphone 11 pro max makes the exynos note 9 look like a total utter joke - faster, smoother with NOT A SINGLE frame drop no matter what you do, gaming is insanely good with surprise - NOT A SINGLE frame drop, battery life is x3 times better, apps have MORE features and runs super smooth and great, speakers destroys the note 9 one, camera too is times better, materials are a lot better too, faceid is super good and fast - feels like I don't have any security on - never failed or gave me any issue. Fun fact, note 9 came with fortnite and recommended as gaming phone for that game. My exynos variant can't run smoothly the game even with 30fps cap medium settings and !1080p! while iphone XS max runs it 60fps high 2688x1242 without a single frame drop. Same goes for the 11 pro max, obviously.

    As for ios - it improves massively and adds more and more missing features/drops restrictions with every version. ios 14 is already known to drop more. I prefer android, because I can do more + I love oneUI, but that doesn't change the fact that in my country I will receive exynos and 1.5 years of decent support. And in the end of the day - I spend my time in apps, not in the settings menu and apps on ios are better, with more features, smoother, a lot of them exclusive to the platform. Can you play dead cells on your android device? No? Yeah, the port is expected around the end of the year, I have it from June 2019. Full blown civilization 6 on your android device? Yeah, will never come, I have it and it's 1:1 port that runs great. Can go on and on and on. If you spend your time tweaking settings, options, UI - good for you, I spend my time in games and apps.
    Reply
  • iSeptimus - Sunday, April 12, 2020 - link

    They really don't. 2 years max on updates and the security patches only come out when it is critical after that.

    My Galaxy Fold only just got One UI 2.1 and Android 10. The most expensive phone they do and they are already slowing down updates for it. Samsung suck at software.
    Reply

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