Google is set to debut its first in-house smartphone chipset, the Tensor SoC, in its upcoming Pixel 6 and Pixel 6 Pro phones. And if the latest report from XDA is correct, the Tensor’s rumored CPU setup could be very, very weird — even by Google standards.

So far, Google has largely been hyping up the Tensor SoC’s AI performance; but it hasn’t revealed any information on the basic CPU and GPU specs of the chip. Google’s Rick Osterloh would only tell The Verge that “the standard stuff people look at will be very competitive and the AI stuff will be totally differentiated.”

Some aspects of the Tensor’s components have already come to light. An earlier XDA report notes that the Pixel 6 will likely use an off-the-shelf Arm Mali-A78 GPU design (which Samsung uses on its flagship Exynos 2100), while Reuters reports that Google will be sourcing its 5G modem from Samsung.

But the CPU still remained a mystery, until today, when XDA published a report based on both a Geekbench score and a source who claims to have an actual Pixel 6 Pro. The report claims that the CPU setup on the Tensor will consist of two Cortex-X1 performance cores clocked at 2.802GHz, two Cortex-A76 performance cores clocked at 2.253GHz, and four Cortex-A55 efficiency cores.

Image: Google

If you’ve been keeping up with major flagship smartphone chips, that’s a very weird list to see, one that mixes together powerful new cores with weaker old ones. Let’s take a step back to explain why:

When we’re looking at most smartphone SoCs, there are generally two main parts: performance CPU cores and efficiency CPU cores. Arm-based designs tend to mix those together in big.LITTLE configurations, to allow for devices that can ramp up performance by using the more powerful “big” cores for intensive things like gaming, while running less demanding tasks (like checking your email) on the “little” efficiency cores to prolong battery life.

A typical Arm-based design might include four performance cores (like the Cortex-A78) and four efficiency cores (like the Cortex-A55). But last year, Arm added a new, even more powerful performance option for chip makers to use: the Cortex-X1.

So, the top smartphones of 2021 tend to offer a triple-cluster design: the Snapdragon 888 uses partially customized versions of a single Cortex-X1, three Cortex-A78, and four Cortex-A55 cores, while Samsung’s Exynos 2100 uses a similar configuration. Tensor, on the other hand, is said to offer two Cortex-X1 cores, two Cortex-A76 cores, and the usual four Cortex-55 cores.

Which makes for a very strange version of a triple cluster design. By including not one, but two Cortex-X1 performance cores, Tensor could theoretically allow it to outclass even the best chips from Qualcomm and Samsung, on paper, if not for the second half of the rumor, which is that Google is also using two older Cortex-A76 cores… which, simply put, doesn’t make any sense.

As XDA points out, the Cortex-A76 was introduced in 2018 and is a full two generations behind the Cortex-A78 design used in 2021’s flagship chips. There’s no immediately logical reason why Google would use the older design, either; the A78 is both faster and more efficient than its older counterpart, making it an extremely strange choice to include as part of the Tensor CPU cluster, especially if Google is already going all out with two X1 cores.

There is the chance that Google is simply obfuscating its CPU design in the Geekbench score, although the report does note that it would be unlikely.

For now, though, the mystery of the Pixel 6’s Tensor chip has gotten even weirder. And it’ll likely stay that way, too, until Google reveals more information when the phones arrive later this fall.