SPEC2006: Performance Parity At Different Efficiency

Having shed a bit of light on the new microarchitectural aspects of the memory subsystems of the new Snapdragon 855 and Exynos 9820, the question is now how the new chipsets perform in more significant macro workloads. For a continued reference CPU workload we’re again falling back to using SPEC.

The SPEC harness we’re using is compiled with simple and straightforward “-Ofast” compilation flag with the Android devices having an instruction tuning to Cortex-A53s as I’ve found this to give the highest average scores across a the wide range of SoCs.

It’s to be noted that SPEC2006 has been deprecated in favour of SPEC2017, however as the 2006 variant is well understood in terms of its workload characterisation for this article I’m still sticking the older version. We’ll be switching over to SPEC2017 later this spring/summer and covering any new data in a separate article.

In the SPECint2006 suite of integer workloads, both chipsets don’t showcase any big surprises in performance. The new Snapdragon 855 variant of the Galaxy S10+ confirms the performance figures we were able to measure on the QRD platform back in January with little to no deviation. The Snapdragon posted excellent performance improvements over the Snapdragon 845 of last year and ties in with the Kirin 980 as the fastest Android SoCs for this year.

The Exynos 9820’s performance figures are also relatively unsurprising for me as I had muted expectations. Here we do see some relatively healthy performance improvements considering that we’re talking about mostly IPC gains on the part of the new Cheetah cores, as the new chipset is a mere 30MHz faster than last year’s chip.

The biggest improvements are found in 429.mcf as well as 471.omnetpp where the new M4 cores perform respectively 32% and 27% better. Both these workloads are the most latency and memory sensitive workloads in the SPECint2006 suite, so given the new chip’s improved memory subsystem it’s no wonder that it’s here where we see the biggest performance jumps. Mcf is also one of the rare tests where the Exynos manages to beat the Cortex A76’s in the S855 and K980 by a more significant amount. Unfortunately for the rest of the workloads being tied is the best-case scenario as it loses out by a small amount in all other workloads.

One thing that I have to note is that it’s possible that big parts of the benchmark probably weren’t run at the peak 2.73GHz clocks of the new M4 cores. Samsung has now enabled a current limiter circuit on the CPU cores and will now more aggressively throttle down the frequency of the CPU in high-power workloads. This means that needy workloads will only see the peak frequencies in the range of 5-10 seconds before throttling down to frequencies of 2.3-2.5GHz. I didn’t have time to have a more thorough monitoring of what the chip is doing during SPEC so it’s something I’ll have to follow up on.

When it comes to power efficiency, the new Exynos 9820 does improve notably compared to last year’s Exynos 9810. It seems that the biggest power efficiency improvements happened on the most memory intensive workloads, in particular 462.libquantum’s 74% efficiency improvement all while improving performance is quite impressive.

Having said that, as I had theorized back based on Samsung’s own marketing numbers, the efficiency gains just aren’t enough to actually compete against the 7nm Cortex A76 cores in the new Snapdragon and Kirin chipsets as Samsung’s chip loses out in every workload.

In the C/C++ workloads of SPECfp2006 we see a similar picture as in the integer workloads. The Snapdragon 855 distinguishes itself here as being able to distance itself more from the Kirin 980 in a few workloads such as 447.dealII and 453.povray, all while maintaining almost equal excellent power efficiency.

The Exynos 9820 here has a hard time showcasing big performance improvements compared to its predecessor, but the one workload where we see a massive jump is 470.lbm, with an 84% jump in performance compared to the M3 cores of last year. This workload is particularly latency and bandwidth intensive so the new load/store unit arrangement of the M4 cores seem to favour it a lot.

In terms of power efficiency, what is interesting is that the new Exynos doesn’t lose as badly as in some of the integer workloads, although it still very much loses to the Snapdragon and Kirin.

Again to have a wider range of performance comparison across ARMv8 cores in mobile here’s a grand overview of the most relevant SoCs we’ve tested:

Finally it’s important to have a wider overview of the performance and efficiency of the current generation chipsets:

In the SPECint2006 geomean score, the Exynos 9820 slightly loses out in the to the Snapdragon 855. More importantly, it uses 47% more energy and power to achieve this same performance. In SPECfp2006 this efficiency difference drops to 21% - although the performance on the M4 cores is also 7% less.

What is most interesting about the new Snapdragon 855 and Exynos 9820 chips is that they have multiple CPU groups, so I went ahead and also measured performance and power of the middle Cortex A76 cores of the Qualcomm chipset against the Cortex A75 cores of the Samsung silicon.

Unexpectedly, the Snapdragon chipset’s “middle” cores beat the Exynos’ middle cores by a hefty amount. At 2.4GHz, the three middle cores of the Snapdragon actually aren’t weak by any means, and only fall behind the Prime core by 15-19% in performance, for an 18% frequency deficit. The Cortex A75 cores on the Exynos chip are 35% weaker than the middle cores of the Snapdragon. Here a more even comparison probably would have been the 1.92GHz middle A76 cores of the Kirin 980, however I wasn’t able to benchmark them separately on Huawei’s devices.

Energy efficiency of Samsung’s A75 cores are good – although it comes at a larger performance deficit, they’re in line with the energy consumption of the A76 cores in the competition.

In the quest to find an answer on how much the actual process node impacts power efficiency between the 7nm Snapdragon and 8nm Exynos, I also went ahead and ran SPEC on the Cortex A55 cores of both chipsets. After a gruelling 11.5 hours of runtime we finally see that the little cores only post a fraction of the performance of the big core siblings. What is actually quite embarrassing though is that the power efficiency is also quite atrocious for the given performance. Here other blocks of the SoC as well as other active components are using up power without actually providing enough performance to compensate for it. This is a case of the system running at a performance point below the crossover threshold where racing to idle would have made more sense for energy.

Apple’s small cores are just such an incredible contrast here: Even though the absolute power isn’t that much bigger than the Cortex A55 cores, the Tempest and Mistral cores are 2.5x faster than an A55, which also results in energy efficiency that is around 2x better.

Finally getting back to the reason why I measured the A55 cores: The Exynos 9820 here again loses out not only in performance but also in power efficiency. Even though the chip’s A55 cores are clocked in higher at 1.95GHz, it’s likely the lack of L2 caches is handicapping the CPUs in IPC, and thus falls behind the 1.78GHz Snapdragon A55’s. Power efficiency here is better on the Snapdragon SoC by 15-18%.

During last summer’s Hot Chips presentation of the M3 CPU core Samsung had remarked to me that the M4 would be the competing against the Cortex A76, and not the M3. While in terms of power efficiency there’s the matter of us not having a valid apples-to-apples process node comparison at hands, at least from a performance perspective it doesn’t look like the new M4 cores are all that impressive, as they just barely manage hold up against the A76 in the Snapdragon and Kirin. Samsung’s CPU just looks to still have too many rough edges and bottlenecks, and thus ends up performing far below of what we’d expect of a microarchitecture that fundamentally on paper is wider than Arm’s Cortex A76.

Memory Subsystems Compared - Bandwidth & MLP Inference Performance: APIs, Where Art Thou?
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  • Andrei Frumusanu - Monday, April 1, 2019 - link

    We don't have any good methodology on things like signal, network (does any site test this *accurately*?).

    As for the UI bits, it's something I wanted to have in the piece but also didn't want to further delay the article another week. In general OneUI is Samsung's by far best user interface and has fantastic features without them feeling like gimmicks. It's currently in my opinion the best variant of Android, though I'm sure some Google users will get angry at me for saying that.
  • GreenMeters - Monday, April 1, 2019 - link

    "If you’re a reader in the US or other Snapdragon markets, you can stop reading here and feel happy about your purchase or go ahead and buy the Galaxy S10+."

    Unfortunately, no, you can't feel happy about it, because once again the Snapdragon variant has its bootloader locked. So your expensive purchase that could easily have a 5+ year lifespan with an open source OS providing up-to-date security and features is now artificially limited to 2 years of Samsung's lousy support.
  • XelaChang - Monday, April 1, 2019 - link

    Quite disappointing for Exinos, especially the audio. Going to look into Huawei P30 instead.
  • Quantumz0d - Monday, April 1, 2019 - link

    Hello Andrei, huge thanks for the solid piece. I don't think there are any editors out who does this type of analysis. The most superb part was the battery analysis, just fantastic. I remember your piece on the Note 9 as well.

    Because smartphones with soldered/sealed batteries are a pain with 2 Yr EOL of cycles due to aggressive current/power/volts/cycles. I wish when you cover the LG. Maybe kindly have a look at their Qnovo. Replacing at end user is so bad, ruins the IP rating and hard to source. Samsung improvising this is a really good news.

    Next the Camera Hole points all are valid. Its worse than a notch with that absurdly thicc status bar and the stupid icons on the right side. An eye sore with dead pixels. Samsung showed in China for an under screen camera perhaps the Vertical integration you mentioned due to the Exynos applies here as well, perhaps the cost as well..

    One UI though perhaps feels polished but its too childish/kid friendly to me and excessively rounded like iOS instead of stock Pie/Q, that is bad IMO.

    Still have to read up on the Camera/Display. Also I think you should mention one great advantage that Exynos has - Bootloader Unlock. Without that QSD version is just a paperweight, zero ownership, zero tuning. IMO a brick.

    Also good to hear about the speaker system performance, apple mentions it always its surprising how they didn't yet offered a good quality, finally those AKG buds are very very bad. I heard them, their tiny driver is horrible in low end and mid range, its shameful. I'm not up to date with recent audio progress but at $100 we can get RHA MA 750/ Final Audio / iBasso IT01/ TFZ King II / Mee Audio P1 / FiiO F9 and Pro / Dunu Titan1 and ton of IEMs with far more superior quality.

    I hope they get the damn AKM chips into their phones and compete with LG ESS and take the Audio seriously, its a shame that LG doesn't advertise ESS anymore but Meridian collaboration.

    Finally the Audio DAC part, sometimes being 100% accurate doesnt necessarily mean best, my iPod 5.5G Wolfson DAC before CL merger many people say the iPod 6G+ Classics are better due to the ball roll off they mention on the Wolfson 5.5G DAC, I have both of them running same OS (Aftermarket stable Linux based Rockbox) and the Cirrus Logic G classic sounds fatiguing to me, metallic and lack of thump vs the 5.5G. I think maybe your impression is also similar. I heard the 835s Acoustic in my Car with my friend's Note 8 US version and it was hollow and lack of any texture and rumble. The iPod beats it by a HUGE margin both of th 6G and 5.5G and 5.5G being better, the V30s ESS sounds more balanced vs the 5.5G as in clear at the expense of soundstage (in car more significant) and sharpness being higher but retains excellent sub bass. All this is subjective. Just to let you know..

    Thanks.
  • Quantumz0d - Monday, April 1, 2019 - link

    Correction.

    > Apple mentions it always its surprising how they didn't yet.

    Apple stands at top as one of the best speakers on an iPad/iPhone.
  • Andrei Frumusanu - Tuesday, April 2, 2019 - link

    The iPhone XS improved it, but the S10 beats it handily in speaker quality.
  • Quantumz0d - Tuesday, April 2, 2019 - link

    Wow, that's really surprising and great news. Thank you for the information. I'll stop by to a Best buy near to me and check it out.

    Perhaps they'll improve on their new S5 855 Tablet (hopefully with jack, unlike S5e) because the Tab S4 is outright beaten to pulp by iPad Pro 2017.
  • s.yu - Friday, April 5, 2019 - link

    Wow beating Apple at audio is definitely something special.
  • Quantumz0d - Monday, April 1, 2019 - link

    Damn another typo

    >Ball roll off

    Its Bass Roll off. And 6G missing before "classic sounds"
  • watersb - Tuesday, April 2, 2019 - link

    What an incredible opportunity to compare two leading SoC architectures.

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