Google did not build the Tensor Processing Unit in public. When it announced the chip on May 18, 2016, it stated it had “been running TPUs inside our data centers for more than a year.” The 2017 ISCA paper “In-Datacenter Performance Analysis of a Tensor Processing Unit” confirms the chip had been “deployed in datacenters since 2015.” By the time of the reveal, TPUs were already accelerating live products including search ranking, Street View, and AlphaGo, the system that defeated Go champion Lee Sedol.