Also Fugaku (The world's #1 supercomputer from 2020 till present) uses HBM2 for its CPU <-> Memory.

https://en.wikipedia.org/wiki/Fugaku_(supercomputer)

(On-package, rather than on-die.)

Wow, okay then. I wonder if that sort of setup will be like the quad itanium motherboard setups that needed massive sustained airflow to keep running...