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
POST A COMMENT

137 Comments

View All Comments

  • Suraj tiwary - Sunday, April 12, 2020 - link

    When will u start testing with Spec2017? Even arm despite being a marketer of its SOC uses both (spec2017 shows less scores) & U despite being a reviewer are too late. Reply
  • xGeoThumbs - Thursday, April 16, 2020 - link

    I always come to these reviews for the photography comparison. They are done really well. Really surprised by the oversharpening on the Snapdragon model compared to the Exynos. The Pixel 4 would also do much better if you find the time to use the Night Sight feature during daytime photography. It improves white balance and detail rendition. Keep it up! Reply
  • damianrobertjones - Thursday, April 23, 2020 - link

    The Amazon reviews, for this phone aren't the best in the world. Reply
  • Junphy - Thursday, May 7, 2020 - link

    Why not add Mediatek Dimensity 1000 for a comparison ? Reply
  • hemingway9000 - Saturday, June 6, 2020 - link

    Hi,
    could you guys somehow please investigate this? https://www.youtube.com/watch?v=h4F0L-soM1I

    It seems that this "Game Optimizer Service" seems to be behind the problems caused in the s20 performance. It would be great if you could do a deep dive into it. Thank you.
    Reply
  • Archer_Legend - Thursday, August 13, 2020 - link

    Usaul amazing rewiew, i read it again after 6 months and it is done very well Reply
  • spicekitkat - Monday, October 5, 2020 - link

    Great article, when a phone comes out I'm really interested in the sound of that phone, hope it will have this sound: https://chakushinon123.com/samsung-s20-ultra/ Reply

Log in

Don't have an account? Sign up now