Ever since the rumors that Google was developing its own chip for Pixel phones, one of the questions we have been asked over and over again is: what are your specifications? One leak after another has confirmed several developments on the Google Tensor chip, but none has confirmed details about the most important part: the CPU. A recent Geekbench listing of allegedly Google Pixel 6 Pro sparked wild online speculation about the Tensor CPU, and we can finally address some of these theories thanks to our source.
All rumors of Google Tensor to date
First, a bit of context. In early 2020, several Korean sources and US news website Axios reported that Google’s “whitechapel” chip will be designed in cooperation with Samsung and will be manufactured in the 5 nm SLSI process. Rumors at the time claimed that Google’s chip will feature an octa-core ARM processor consisting of two Cortex-A78 + two Cortex-A76 + four Cortex-A55 cores, an ARM Mali GPU available for sale, hardware optimized for machine learning and optimizations for the company’s Google Assistant service. Given the challenges of developing a custom SoC, it made sense for Google to use existing CPU cores for its first mobile chipset, so these spec rumors seemed plausible to many.
Many months passed without news about Google ‘s custom silicon until 9to5Google reported in April that the chip will debut in the Pixel 6 series. Finally, Google last month confirmed its plans to ship the Pixel 6 series with its internal chip, called Google Tensor. They also confirmed some high-level details about the chipset, such as how its TPU is used to run HDRNet on every frame of a video, how the chip powers the new artificial intelligence features on the device, and how the chip protects data from users with second-generation Titan M2 module.
Google’s surprise announcement in early August confirmed most of the leaked information last year, while confirmation of some of the remaining rumors came from other leaks. A comment left by Google on the Google Issue Tracker confirmed the news about the Mali GPU, which we now know is the Mali-G78. A breakdown of a beta version of Android 12 revealed that the Pixel 6 will have a Samsung Exynos modem, which was later corroborated by Reuters. The last remaining specification that had yet to be confirmed was the CPU, which is why so much attention was paid to this list of Geekbench.
The Geekbench result that many assumed came from the Pixel 6 Pro. While we can never be 100% sure, we are firmly committed to making this benchmark legitimate. The build fingerprint, kernel version string, CPU frequencies, CPU clusters, GPU information and more match the values of our source Pixel 6 Pro. It would be very unlikely that anyone would have falsified this listing, which would be possible, but it requires the person to know the exact values to deceive our source that has real hardware.
Based on incomplete CPU information from this list, leakers com Digital chat station extrapolated the CPU configuration of the Google Tensor chip. The most shocking part of this speculation for many was the suggestion that the Google Tensor CPU will have two Cortex-X1 cores, Arm’s most powerful Cortex CPU to date. In contrast, neither the Qualcomm Snapdragon 888 nor the Samsung Exynos 2100 have more than one Cortex-X1 core. If this chip also has two Cortex-A78 cores in addition to the dual Cortex-X1 cores, Google Tensor may be the fastest chipset on an Android device to date.
As many have pointed out, the Geekbench score falls well below the average of the Exynos 2100 Galaxy S21 and Qualcomm Snapdragon 888 device, which is strange considering the hardware in question. After speaking with Andrei Frumusanu, chief mobile editor at AnandTech, we came to the conclusion that you he can not come to a conclusion about the true performance of the Pixel 6 Pro just from this benchmark result. As he pointed out in our discussion, it is difficult to know which core was underlined for the single core part of the benchmark, and the core was apparently blocked at 2.15 GHz anyway, which is well below of the maximum frequency of the X1 cores. There are several factors that could have contributed to this outrageous benchmark result, such as non-optimized programmer settings or DVFS, which could have prevented Geekbench from running kernels at their maximum frequencies. If we want to find out how fast the Pixel 6 Pro is, we’ll have to wait for more people with the phone to use the benchmark.
Google Tensor Specifications of a Real Pixel 6 Pro
While the benchmark does not confirm the microarchitectures of Google Tensor CPU cores, we were finally able to determine what the possible designs of each CPU core are thanks to our source. Yesterday, a source who has a real Pixel 6 Pro contacted us and we learned from their device that the three-cluster kernel design and CPU frequencies revealed by the Geekbench list are accurate. After our report yesterday, we found the exact parts of the CPU on the Google Tensor chip, which are exposed to the system via / proc / cpuinfo, a file that occupies the same CPU and that the kernel reads. Therefore, the chances of it being falsified are very low, although there is little chance that Google itself will mask the CPU identifiers of the output. We say it is one low possibility because Google did not bother to impersonate or confuse any other data on the device, but who knows, the parts of the Google Tensor CPU may be the only thing they care about hiding.
Assuming the output was not altered, we have determined that Google Tensor will have the following CPU configuration:
- 2x ARM Cortex-X1 clock at 2,802 GHz
- 2x ARM Cortex-A76 run at 2.253 GHz
- 4x ARM Cortex-A55 clocked at 1.80 GHz
AnandTechAndrei thinks the use of dual X1 cores is reasonable, but he, as well as others we’ve talked about, are perplexed by the apparent use of dual A76 cores. The Cortex-A76 was announced in mid-2018 and was succeeded by the A77 and, more recently, the A78, which is significantly better in terms of power, performance and area (PPP). We find it hard to rationalize why Google may have chosen to go with two A76 cores instead of two A78 cores when there is very little benefit in doing so. We even checked the cpuinfo output of various Qualcomm and Exynos devices just to make sure the results were as expected and that we were not misinterpreting the output of the Pixel 6 Pro. We would like it to be shown to be wrong in this statement, but there is no doubt that this CPU configuration is the one that suggests the cpuinfo output of a real Pixel 6 Pro device.
An important detail that we do not know is the amount of cache available for the CPU cores. A large cache is important enough for kernels to achieve the performance that Arm claims it can.
In addition, we still do not know the number of GPU cores, which is difficult to find, as the information is not easily exposed to the system. We previously learned that the Pixel 6 will have the same GPU design as the Exynos Galaxy S21: the ARM Mali-G78 – a fact that we can corroborate through real hardware. The GPU can be registered to up to 848 MHz, although without knowing the number of cores, we do not know the performance of the phone compared to other devices with this GPU.
ARM Mali-G78
In our previous report, we confirmed that Google Tensor includes the “g5123b” modem, which most likely refers to Samsung’s Exynos 5123 modem. We also reported that the phone supports Wi-Fi 6E (i.e. Wi-Fi at 6 GHz), has a voltage processing unit (TPU) called “abrolhos” with a maximum of 1,230 GHz, will be paired with a 12 GB LPDDR5 RAM module, and will also feature at least one storage variant with 128 GB of UFS storage. The phone will also have a UWB radio for short-range location tracking and digital car key support, among other features.
Decode AV1, other news
The Pixel 6 Pro ships with Google AV1 Decoder (c2.google.av1.decoder), which is accelerated by hardware using the Google Tensor chip. The device can decode AV1 content with a resolution of up to 4K and 60 fps. You can also decode HEVC content at a resolution of up to 4K and 120 fps or 8K resolution and 30 fps. In comparison, the Samsung Exynos 2100 can decode AV1 content with a resolution of up to 8 K and 30 fps, or HEVC content with a resolution of 8 K and 60 fps. Still, the fact that the Google Tensor chip is compatible with hardware-accelerated AV1 decoding is significant, as so far all Qualcomm Snapdragon chips and, by extension, Google’s past Pixel phones, don’t support this feature.
That Google chose to include HW AV1 decoding on its own Google Tensor chip should come as no surprise, as the company has been one of the biggest proponents of the copyright-free video codec. The company’s push to require AV1 support was one of the main grievances cited by Roku when it removed the YouTube TV app from its platform.
Speaking of codecs, our source confirmed to us that the Pixel 6 Pro is compatible both aptX and aptX HD codecs, two Bluetooth audio codecs used by many wireless headsets on the market. These codecs must be licensed by Qualcomm, so some of our readers were worried that the Pixel 6 series would not support them as they do not have Snapdragon chips. A Snapdragon chip is not required to support aptX, so these concerns were mostly unfounded. However, it is still good to confirm that the Pixel 6 series will support high quality Bluetooth audio. Sony’s LDAC is also supported.
Finally, our source confirmed something we already suspected: There is no video output on the Pixel 6 Pro. Google has again opted not to implement the alternative DisplayPort mode, which allows a DP video signal to be sent via the USB-C port. Android has had a barebones desktop mode for some versions now, but it looks like Google doesn’t want to have anything to do with it. This is unfortunate because the phones are more than powerful enough to handle day-to-day tasks for an average user, and with 12GB of RAM, the Pixel 6 Pro can easily handle all of your multitasking needs.