CPU Performance & Efficiency: SPEC2006

We move on with our analysis by using SPEC2006 on the Snapdragon 855 QRD. SPEC2006 is an important benchmark as not only does it represent a tool that is used by many companies to architect their CPU designs, but it also a very well understood and academically documented workloads that can serve as a macro-benchmark to determine microarchitectural aspects of a CPU and system.

It’s to be noted that SPEC2006 has been deprecated in favour of SPEC2017, and although we’ll switch to that at some point, for mobile platforms SPEC2006 still represents a good benchmark. Because our scores aren’t official submissions, as per SPEC guidelines we have to declare them as internal estimates from our part.

A Big Note on Power on the QRD

Although for this article I was able to collect power figures for both CPU and GPU workloads, the figures are not of an as high certitude as when measured on commercial devices. The reason for this is that much like last year’s Snapdragon 845 QRD, this year’s 855 platform reports rather high idle power in the 950-1050mW range, about 500mW more than one would expect in a final product. Because our power measurement methodology represents publishing active system power, meaning we measure total power during a given workload and subtract the idle power under the same conditions, there is a degree of uncertainty if the idle power by default is quite high.

Today’s power efficiency figures thus merely represent a guideline – and we’ll make sure to re-test the results once we get our hands on final commercial devices.

The Results – The Snapdragon 855 Performs Admirably

We’ll start off with the aggregate results and drill down in the detailed results later:

The Snapdragon 855 ends up performing extremely well, ending up neck-and-neck with the Kirin 980’s performance, which shouldn’t come as too big of a surprise.

In SPECint2006, the Snapdragon 855 performs 51% better than the Snapdragon 845, all while improving power efficiency by 39% over its predecessor. Against the Kirin 980 which is currently its nearest Android competitor, the Snapdragon just slightly edges ahead by 4%.

In SPECfp2006, the Snapdragon 855 shows an even bigger 61% leap over the Snapdragon 845, and also manages to better showcase the 9% clock speed advantage over the Kirin 980, sporting a similar performance lead.

Again what is most important in these results is the power efficiency figures. One of the things that had me worried during Qualcomm’s Snapdragon 855 launch in Hawaii last month is that the company pretty much avoided talking or publishing any meaningful power efficiency claims on the side of the CPU. Fortunately it seems there wasn’t any need to be concerned as the Snapdragon 855, at first glance, seems to be extremely efficient even on the high clocked 2.85GHz Prime core.

Detailed Results

Drilling down into the detailed results, the one comparison that is most interesting is the performance of the Snapdragon 855 against the Kirin 980. On one hand the Snapdragon 855 is clocked 9% higher as well as promises some tuned microarchitectural characteristics which promise to improve IPC – while on the other hand HiSilicon’s implementation is more straightforward and brings with itself a bigger L3 cache as well as memory latency advantages.

In the vast majority of workloads, both chipsets are neck-and-neck, only diverging in some key aspects. In less memory hierarchy demanding workloads, the Snapdragon more easily is able to showcase its clock speed advantage. In more latency sensitive workloads, this difference shrinks or reverses. 462.libquantum is an interesting result as Qualcomm commented that its lead here is primarily due to the customisations made on the CPU core – although they wouldn’t exactly specify which aspect in particular is bringing the boost.

The biggest performance discrepancy on the negative side of things is the 13% disadvantage in 458.sjeng – the benchmark is most sensitive to branch mispredictions and again here Qualcomm has stated they’ve made changes to the branch data structures of the core.

What is most odd for me to see as a result, is the fact that 429.mcf performs admirably well on the Snapdragon 855 – which goes against intuition given the platform’s memory latency disadvantage. It is possible here that the Snapdragon 855 performs better than the Kirin 980 due to its better L3 cache latency?

On the SPECfp2006 results, the results can be very clearly categorised into two sets: In one set the Snapdragon 855 clearly showcases a healthy advantage over the Kirin 980, up to very notable 17% and 22% leads in 447.dealII and 453.povray. In the other set, the Snapdragon is again neck-and-neck with the Kirin 980, and these happen to again be the workloads that are most memory sensitive in the FP suite.

Overall, the Snapdragon 855’s CPU performance does not disappoint. Performance on average is ahead of the Kirin 980, although not by much. Here both chipsets are most of the time neck-and-neck, and it will mostly depend on the workload which of the two will take the lead.

More important than performance, the efficiency of the Snapdragon 855 is top-notch, exceeding what I had expected from the higher clock implementation of the chip. There is still a degree of uncertainty over the power numbers on the QRD platform, but if these figures are representative of commercial devices, then 2019’s flagship will see excellent battery life.

Introduction & Specifications Inference Performance: Good, But Missing Tensor APIs
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  • Midwayman - Wednesday, January 16, 2019 - link

    People would have said that about AMD not long ago.... Just saying.
  • 29a - Wednesday, January 16, 2019 - link

    They used the same engineer, Jim Keller. He works for Intel now.
  • Midwayman - Wednesday, January 16, 2019 - link

    Eventually, sure. Apple will stall out on process related stuff eventually and they'll have a chance to catch up. Unlikely until then as they're still making big gains too and have a 2-3 year lead.
  • jjj - Tuesday, January 15, 2019 - link

    We need a bit more on the GPU side in the next years for foldable. Pixel count will increase, SoC power needs to decrease (more power and mechanical volume goes towards the display) and mobile gaming should gain in popularity with x2+ larger displays.
  • levizx - Tuesday, January 15, 2019 - link

    We can establish that single core performance/power is good, but what about multi-core? Wouldn't the other 3 big core be running at the highest voltage while potentially running at ~2GHz in real world workload?
  • Andrei Frumusanu - Tuesday, January 15, 2019 - link

    Correct. We'll have to see how efficiency performs once we get commercial devices.
  • Chaser - Tuesday, January 15, 2019 - link

    We read about all this when the 845 was about to launch a year ago. I didn't see some monumental improvement in responsiveness or efficiency despite all these whitepapers stating so. Unless you are so kind of smartphone gaming fanatic, real-world use differences between each year look great mostly on paper.
  • SquarePeg - Tuesday, January 15, 2019 - link

    Performance has been good enough since 2013 with the release of the SD 800. Every year we get a performance bump that just gets offset by feature bloat that doesn't really improve performance outside of benchmarks. I can pull out my old LG G2 running an Android 4.4.2 custom ROM/kernel and that thing just flies compared to any phone from the past year.
  • A5 - Tuesday, January 15, 2019 - link

    I promise you it won’t. SD 800 will feel terrible
  • yeeeeman - Wednesday, January 16, 2019 - link

    I have a Z3 compact, which is a SD801. Bought recently a Galaxy S7 second hand to replace the Z3. I can safely say that the Exynos 8890 is noticeably faster in opening apps, playing intensive games and generally in multitasking. Z3 usually lags when phone is started for first time and many apps sync. Galaxy S7 is buttery smooth. So yeah, I think we can feel the progress in performance of these chips, but maybe at a later point when apps get to their limit of computing power. Then you actually see that a newer chipset is noticeably faster.
    But nevertheless, the Z3 compact with SD801 is still a great fast phone. It runs a bit slower than the Exynos as I said but in general it is not slow at all on Android 6.0. So yeah, a chipset like it could be easily used in today's times if you don't a bit of slow down here and there.

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