CPU Performance & Power

On the CPU side of things, the Tensor SoC, as we discussed, does have some larger configuration differences to what we’ve seen on the Exynos 2100, and is actually more similar to the Snapdragon 888 in that regard, at least from the view of a single Cortex-X1 cores. Having double the L2 cache, however being clocked 3.7%, or 110MHz lower, the Tensor and the Exynos should perform somewhat similarly, but dependent on the workload. The Snapdragon 888 showcases much better memory latency, so let’s also see if that actually plays out as such in the workloads.

In the individual subtests in the SPEC suite, the Tensor fares well and at first glance isn’t all too different from the other two competitor SoCs, albeit there are changes, and there are some oddities in the performance metrics.

Pure memory latency workloads as expected seem to be a weakness of the chip (within what one call weakness given the small differences between the different chips). 505.mcf_r falls behind the Exynos 2100 by a small amount, the doubled L2 cache should have made more of a difference here in my expectations, also 502.gcc_r should have seen larger benefits but they fail to materialise. 519.lbm_r is bandwidth hungry and here it seems the chip does have a slight advantage, but power is still extremely high and pretty much in line with the Exynos 2100, quite higher than the Snapdragon 888.

531.deepsjeng is extremely low – I’ve seen this behaviour in another SoC, the Dimensity 1200 inside the Xiaomi 11T, and this was due to the memory controllers and DRAM running slower than intended. I think we’re seeing the same characteristic here with the Tensor as its way of controlling the memory controller frequency via CPU memory stall counters doesn’t seem to be working well in this workload. 557.xz_r is also below expectations, being 18% slower than the Snapdragon 888, and ending up using also more energy than both Exynos and Snapdragon. I remember ex-Arm’s Mike Filippo once saying that every single clock cycle the core is wasting on waiting on memory has bad effects on performance and efficiency and it seems that’s what’s happening here with the Tensor and the way it controls memory.

In more execution bound workloads, in the int suite the Tensor does well in 525.x264 which I think is due to the larger L2. On the FP suite, we’re seeing some weird results, especially on the power side. 511.povray appears to be using a non-significant amount lesser power than the Exynos 2100 even though performance is identical. 538.imagick also shows much less power usage on the part of the Tensor, at similar performance. Povray might benefit from the larger L2 and lower operating frequency (less voltage, more efficiency), but I can’t really explain the imagick result – in general the Tensor SoC uses quite less power in all the FP workloads compared to the Exynos, while this difference isn’t as great in the INT workloads. Possibly the X1 cores have some better physical implementation on the Tensor chip which reduces the FP power.

In the aggregate scores, the Tensor / GS101 lands slightly worse in performance than the Exynos 2100, and lags behind the Snapdragon 888 by a more notable 12.2% margin, all whilst consuming 13.8% more energy due to completing the task slower. The performance deficit against the Snapdragon should really only be 1.4% - or a 40MHz difference, so I’m attributing the loss here just to the way Google runs their memory, or maybe also to possible real latency disadvantages of the SoC fabric. In SPECfp, which is more memory bandwidth sensitive (at least in the full suite, less so in our C/C++ subset), the Tensor SoC roughly matches the Snapdragon and Exynos in performance, while power and efficiency is closer to the Snapdragon, using 11.5% less power than the Exynos, and thus being more efficient here.

One issue that I encountered with the Tensor, that marks it being extremely similar in behaviour to the Exynos 2100, is throttling on the X1 cores. Notably, the Exynos chip had issues running its cores at their peak freq in active cooling under room temperature (~23°C) – the Snapdragon 888 had no such issues. I’m seeing similar behaviour on the Google Tensor’s X1 cores, albeit not as severe. The phone notably required sub-ambient cooling (I tested at 11°C) to get sustained peak frequencies, scoring 5-9% better, particularly on the FP subtests.

I’m skipping over the detailed A76 and A55 subscores of the Tensor as it’s not that interesting, however the aggregate scores are something we must discuss. As alluded to in the introduction, Google’s choice of using an A76 in the chip seemed extremely hard to justify, and the practical results we’re seeing the testing pretty much confirm our bad expectations of this CPU. The Tensor is running the A76 at 2.25GHz. The most similar data-point in the chart is the 2.5GHz A76 cores of the Exynos 990 – we have to remember this was an 7LPP SoC while the Tensor is a 5LPE design like the Eynos 2100 and Snapdraogn 888.

The Tensor’s A76 ends up more efficient than the Exynos 990’s – would would hope this to be the case, however when looking at the Snapdragon 888’s A78 cores which perform a whopping 46% better while using less energy to do so, it makes the Tensor’s A76 mid-cores look extremely bad. The IPC difference between the two chips is indeed around 34%, which is in line with the microarchitectural gap between the A76 and A78. The Tensor’s cores use a little bit less absolute power, but if this was Google top priority, they could have simply clocked a hypothetical A78 lower as well, and still ended up with a more performant and more efficient CPU setup. All in all, we didn’t understand why Google chose A76’s, as all the results end up expectedly bad, with the only explanation simply being that maybe Google just didn’t have a choice here, and just took whatever Samsung could implement.

On the side of the Cortex-A55 cores, things also aren’t looking fantastic for the Tensor SoC. The cores do end up performing the equally clocked A55’s of the Snapdragon 888 by 11% - maybe due to the faster L3 access, or access to the chip’s SLC, however efficiency here just isn’t good, as it uses almost double the power, and is more characteristic of the higher power levels of the Exynos chips’ A55 cores. It’s here where I come back to say that what makes a SoC from one vendor different to the SoC from another is the very foundations and fabric design - for the low-power A55 cores of the Tensor, the architecture of the SoC encounters the same issues of being overshadowed in system power, same as we see on Exynos chips, ending up in power efficiency that’s actually quite worse than the same chips own A76 cores, and much worse than the Snapdragon 888. MediaTek’s Dimensity 1200 even goes further in operating their chip in seemingly the most efficient way for their A55 cores, not to mention Apple’s SoCs.

GeekBench 5

While we don’t run multi-threaded SPEC on phones, we can revert back to GeekBench 5 which serves the purpose very well.

Although the Google Tensor has double as many X1 cores as the other Android SoCs, the fact that the Cortex-A76 cores underperform by such a larger degree the middle cores of the competition, means that the total sum of MT performance of the chip is lesser than that of the competition.

Overall, the Google Tensor’s CPU setup, performance, and efficiency is a mixed bag. The two X1 cores of the chip end up slightly slower than the competition, and efficiency is most of the time in line with the Exynos 2100’s X1 cores – sometimes keeping up with the Snapdragon 888 in some workloads. The Cortex-A76 middle cores of the chip in my view make no sense, as their performance and energy efficiency just aren’t up to date with 2021 designs. Finally, the A55 behavioural characteristic showcases that this chip is very much related to Samsung’s Exynos SoCs, falling behind in efficiency compared to how Qualcomm or MediaTek are able to operate their SoCs.

Memory Subsystem & Latency GPU Performance & Power
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  • sharath.naik - Thursday, November 4, 2021 - link

    Good in-depth review. I know you are doing the camera review of this. So I have a request can you look into if the Pixel 6 cameras are hardware binned to ~12MP even though the specs say they are 50MP/48MP. There is a lot of mixed views out there, most mistaking this as the pixel binning done on other phones like galaxy S21u(Software binned for low light but has access to full resolution). If you could confirm this for the review would be great, looking forward to that review.
  • Silver5urfer - Tuesday, November 2, 2021 - link

    Exactly as expected 1:1

    The SoC is a bust, they tried to do some gimmickry with their zero talent and tried to make it a cheaper deal by going to Samsung for their IP fabrication expertise and lithography process. Ended up being a dud in CPU, GPU and price to performance, all that NPU NN, mega magic boom is all a farce. I was asking the same thing, what does these provide to us end users ? Nothing. Just that fancy Livetranslation and other gimmicks which you use seldom. On top we do not even know what TPU does in the Pixel Software, it's closed source. AOSP is open but Pixel UI and all backend are closed.

    Hardware is utter joke, the P6 series has garbage mmwave system look at the internals, they crammed one lol. LG V50 back in 2019 had 2-33 mmwave antennas. This junk saved on cost. The display has banding issues all over the place. Optical image sensor for Fingerprint is slow and a joke vs the physical dedicated ones. The stereo speaker system has massive channel imbalance on top. Then you have the low battery SoT for this price point and battery capacity. The DIY aspect is thrown into gutters, the phone has massively hamfisted cooling approach with graphite pads smeared all over the place as leaks showed and no proper HS system it's just a small pathetic AL board reinforcement plate doing it so on top the Display has no metal backplate to reinforce it or dissipate heat. What a nonsense. SD888 itself heats up a lot and so many vendors add VC cooling, Sony Xperia 1 Mark 3 messed up there and had inferior performance with throttling. This junk is even more pathetic, pay for a S tier SKU get trash sustained performance of a B+ device, the AP, Pocket now and other Youtube shill press will hype this to moon.

    We do not even know how this junk has in terms of Software blocks like P2, P3, P4 had A/B system, then merged partitions, later read only ext4 system. This will have even worse. To make it a round about trash, the software is a joke cheap kiddo inspired garbage, heck that BBKs OnePlus's Oxygen + Oppo Color OS mix is way superior than this junk with massive information density loss.

    I'd wait for the next SD successor device, hopefully 888's BS power consumption and insane heat can be reduced.
  • Silver5urfer - Tuesday, November 2, 2021 - link

    It's a typo for mmwave, it's 2-3 units. Also I forgot to mention the lack of charger, SD slot, no 3.5mm jack very poor servicing almost impossible to get the phone properly cooled if you open it due to cheap graphite pad reliance. It also has that USB port and microphone soldered to the mainboard which looks like a feeble trash unit check any phone in the recent times and look how solid engineered they are, dual sandwich designs with reinforced chassis and proper heat dissipation.
  • goatfajitas - Tuesday, November 2, 2021 - link

    People get WAY too hung up on benchmarks. LOL, a "dud". A phone is about user experience, not how many "geekmarks" = best.
  • lionking80 - Tuesday, November 2, 2021 - link

    I agree that the benchmarks do not tell the whole story, but I would still say that even the use of a Snapdragon 870 would have been a better choice.
    The general performance is similar (maybe a small advantage for Tensor in AI), but the advantages of Snapdragon 870 are bigger: runs much cooler, hugely better battery-life.
    To be honest I am disappointed by the SOC. The only thing that might make it a seller is the software (ui and camera), but the SOC is rather a no-go.
  • goatfajitas - Tuesday, November 2, 2021 - link

    There are other factors though. Early ROM settings, tweaks, bugs, and cooling/hardware. The 870 may have scored lower in a P6 as well. So many factors. - Agreed, the P6 should be a bit more polished though.
  • at_clucks - Tuesday, November 2, 2021 - link

    The problem goes beyond the slightly worse SoC than the already existing Qualcomm offering. It's that despite being a "Google SoC" they still support it for just 3 years. All the excuses used over the years, all the pointing fingers at SoC manufacturers for the lack of support were just proven to be a load of crap. Same crap, now with a google sticker.
  • sharath.naik - Tuesday, November 2, 2021 - link

    It's about to get worse with the camera review. I can verify Google might have been bluffing about the 50mp/48mp sensors. The sensors are locked at 12mp. So Pixel pro has essentially three 12 mp cameras. Which means the portrait mode zoom of 2x is a low resolution 3 MP image. Also at 10x zoom the image resolution is 2.5MP, 4 times lower than that of s21 ultra. What drove Google to make the choice of first hardware pixel binning the resolution down and then trying to digitally blow the resolution backup!!.It's baffling, tried to get an answer from Google support, they just refused to confirm or deny this is binned at the hardware level
  • hoxha_red - Tuesday, November 2, 2021 - link

    "I can verify that google might have been bluffing"

    dude, lmfao—it's called "binning"; please look it up. they've been upfront about this and it was known before the phone was even launched, let alone after we've seen all of these reviews. The reason Google support "refused to confirm or deny" is because the people doing customer support are unlikely to know what "pixel binning" is (hey, I guess they're in good company there with you), and are not equipped to deal with weirdos of your specific variety.
  • Maxpower27 - Tuesday, November 2, 2021 - link

    You obviously have no familiarity with mobile phone cameras and sensors in particular. Read up about them and then try again.

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