Google introduced the Tensor series of chips with the Pixel 6 series in 2021. It was meant to usher in a range of chips specially tailored by Google to keep up with its class-leading AI-based software features. Just three Tensor chips in, and many of Google’s new AI features need to be off-loaded to the cloud for processing.
The earlier phones just used off the shelf Snapdragons. It’s only the 6 and up that use the Tensor chip.