Memory Performance

ARM made several improvements to the A73’s memory system. Both L1 caches see an increase in size, with the I-cache growing from 48KB (A72) to 64KB and the D-cache doubling in size to 64KB. The A73 includes several other changes, such as enhanced prefetching, that should improve cache performance too.

The A73 still has 2 AGUs like the A72, but they are now capable of both load and store operations instead of having each AGU dedicated to a single operation like in the A72, which should improve the issue rate into main system memory.

The Kirin 960’s larger 64KB L1 cache maintains a steady latency of 1.27ns versus 1.74ns for the Kirin 950, a 27% improvement that far exceeds the 2.6% difference in CPU frequency, highlighting the A73’s L1 cache improvements. L2 cache latency is essentially the same, but Kirin 960 again shows a 27% latency improvement over Kirin 950 when accessing main memory, which should be beneficial for the latency sensitive CPUs.

Memory bandwidth results are less definitive, however. The Kirin 960 shows up to a 30% improvement in L1 read bandwidth over the Kirin 950 depending on the access pattern used, although L1 write bandwidth is lower by nearly the same amount. The 960’s L2 cache bandwidth is also lower for both read and write by up to about 30%.

The two graphs above, which show reading and writing NEON instructions using two threads, help to illustrate Kirin 960’s memory bandwidth. When reading instructions, Kirin 960’s L1 cache outperforms the 950’s, but bandwidth drops once it hits the L2 cache. The Kirin 950 outpaces the 960 when writing to both L1 and L2, only falling below the 960’s bandwidth when writing to system memory. This reduction in cache bandwidth could help explain the Kirin 960’s performance regression in several of Geekbench 4’s floating-point tests.

Geekbench 4 - Memory Performance
Single Threaded
  Kirin 960 Kirin 950
(% Advantage)
Exynos 7420
(% Advantage)
Snapdragon 821
(% Advantage)
Memory Copy 4.55 GB/s 3.67 GB/s
(23.87%)
3.61 GB/s
(26.04%)
7.82 GB/s
(-41.84%)
Memory Latency 12.1 Mops/s 9.6 Mops/s
(25.39%)
5.6 Mops/s
(115.67%)
6.6 Mops/s
(81.82%)
Memory Bandwidth 15.5 GB/s 9.2 GB/s
(69.28%)
7.5 GB/s
(105.84%)
13.5 GB/s
(14.53%)

While the Kirin 960’s L1/L2 cache performance is mixed, it holds a clear advantage over the Kirin 950 when using system memory. Memory latency improves by 25%, about the same amount our internal testing shows, and memory bandwidth improves by 69%. The A73’s two load/store AGUs are likely responsible for a large chunk of the additional memory bandwidth, with the Mate 9’s higher memory bus frequency helping some too.

System Performance

Now it’s time to see how Kirin 960’s lower-level CPU and memory results translate into real-world performance, keeping in mind that OEMs can influence the balance between performance and battery life in a number of ways, including adjusting thermal limits and parameters that govern CPU scheduler and DVFS behavior, which is one reason why two devices with the same SoC can perform differently.

PCMark - Work 2.0 Performance Overall

PCMark - Web Browsing 2.0

PCMark - Writing 2.0

PCMark - Data Manipulation 2.0

PCMark includes several realistic workloads that stress the CPU, GPU, RAM, and NAND storage using Android API calls many common apps use. The Mate 9 and its Kirin 960 SoC land at the top of each chart, outpacing the Mate 8 and its Kirin 950 by 15% overall and the top-performing Snapdragon 821 phones by up to 20%.

The Mate 9’s advantage over the Mate 8 is only 4% in the Web Browsing test, but it’s still the fastest phone we’ve tested so far. Integer performance is not the Kryo CPU’s strength, and in this integer-heavy test all of the Snapdragon 820/821 phones fall behind SoCs using ARM’s A72 and A73 CPUs, with LeEco’s Le Pro3, the highest performing Snapdragon 821 phone, finishing 18% slower than the Mate 9.

The Writing test performs a variety of operations, including PDF processing and file encryption (both integer workloads), along with some memory operations and even reading and writing some files to internal NAND, and it tends to generate frequent, short bursts of activity on the big CPU cores. This seems to suit the Mate 9 just fine, because it extends its performance advantage over the Mate 8 to 23%. There’s a pretty big spread between the Snapdragon 820/821 phones; the LeEco Le Pro3, the best performer in the family, is 40% faster than the Galaxy S7 edge, a prime example of how other hardware components and OEM software tinkering can affect the overall user experience.

The Data Manipulation test is another primarily integer workload that measures how long it takes to parse chunks of data from several different file types and then records the frame rate while interacting with dynamic charts. In this test, the Mate 9 is 30% faster than the Mate 8 and 37% faster than the Pixel XL.

Kraken 1.1 (Chrome/Safari/IE)

WebXPRT 2015 (Chrome/Safari/IE)

JetStream 1.1 (Chrome/Safari)

All of the Snapdragon 820/821 phones perform well in the Kraken JavaScript test, pulling ahead of the Mate 9 by a small margin. The P9 uses Kirin 955’s 7% CPU frequency advantage to help it keep up with the Mate 9 in Kraken and JetStream. The Mate 9 still pulls ahead by 11% in WebXPRT 2015, though, and outperforms the Mate 8 by 10% to 19% in all three tests. The Moto Z Play Droid, the only phone in the charts to use an octa-core A53 CPU configuration, cannot even manage half the performance of the Mate 9, which is similar to what our integer IPC tests show.

The Kirin 960 showed mixed results in our lower-level CPU and memory testing, pulling ahead of the Kirin 950 in some areas while falling behind in others. But when looking at system level tests using real-world workloads, the Mate 9 and its Kirin 960 are the clear winners. There are many hardware and software layers between you and the SoC, which is why it’s important not to use an SoC benchmark to test system performance and a system benchmark, such as PCMark, to test CPU performance.

CPU Performance CPU Power Consumption and Thermal Stability
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  • lilmoe - Friday, March 17, 2017 - link

    We've been asking for this for years now... Reply
  • wardrive2017 - Tuesday, March 14, 2017 - link

    Im quiet surprised by the Snapdragon 650 here. That has 2 1.8 ghz a72s and a 180 Gflop gpu on 28nm and manages to stay a little north of 2 watts on the gpu power consumption charts. Upgrade to the Snapdragon 652 with 4 a72s and i bet that is a high mid ranger with little to no throttling. Sustained game performance much closer to the high end than the specs would suggest. Reply
  • wardrive2017 - Tuesday, March 14, 2017 - link

    I wonder about the sustained performance of the snapdragon 625 as well. I understand it has half the single thread performance or less of these flagship SoCs, but its got a Vulkin/ES 3.2 130 Gflop gpu, and 8 homogenous a53's on 14 nm. You know that wont throttle, and its going to be in many devices this year. I wonder what sustained performance it would have after an hour of Modern Combat 5 or something similiar compared to these flagships. Reply
  • wardrive2017 - Tuesday, March 14, 2017 - link

    Nvm i guess a game that the 625 could run wouldnt exactley be pushing these flagships into a higher thermal envelope anyway. Really need an edit button Reply
  • whitecliff90 - Wednesday, March 15, 2017 - link

    28nm is quite mature now, plus the Adreno GPU so you can expect it to give better perf/W. Reply
  • zeeBomb - Tuesday, March 14, 2017 - link

    When you were expecting a deep dive but not this kind of chipset...lecry

    I rather have an A11 or the newer Exynos 8895 w.e it's called dive though!
    Reply
  • zodiacfml - Tuesday, March 14, 2017 - link

    Thanks. It looks to me that the high power consumption was intentional for it to keep up in the benchmarks. Otherwise, it will have great battery life but lower scores. Reply
  • joms_us - Tuesday, March 14, 2017 - link

    SD821 will continue to shine and this article shows it can still compete even with SD835 that will have similar cluster config as Kirin 960. Reply
  • Eden-K121D - Tuesday, March 14, 2017 - link

    The Android SOC ecosystem is not in a very good shape with few bright spots Reply
  • MrSpadge - Tuesday, March 14, 2017 - link

    Yeah.. with the bright spots being Qualcom, Samsung and HiSilicon. Reply

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