How exactly is Google selling TPU's?

Are they selling chips? Are they selling a 'reservation' on GCP to use a TPU?

I hope these really do make a dent in Nvidia's market control. It sucks that it's come routing for Broadcom and Google. I hope at least other companies can license the TPU architecture and supply chips.

Related:

TPUs vs. GPUs and why Google is positioned to win AI race in the long term

https://news.ycombinator.com/item?id=46069048

Ironwood, our latest TPU

https://news.ycombinator.com/item?id=46051345