ICI is interchip interconnect in TPUv4 pods.

You can read more on paper that my collegues in Google platforms recently published https://arxiv.org/abs/2304.01433 https://cloud.google.com/blog/topics/systems/tpu-v4-enables-...

I am so happy this paper is finally out :-) I led the SRE work during their NPI. It's a pain when you have to wait 3 years to discuss what you worked on.

They are based on OCS, which powers Google datacenter networks https://arxiv.org/abs/2208.10041

https://dl.acm.org/doi/pdf/10.1145/3360307 Very fast (hundreds of gigabits per connection) networks that attach TPUs on the same board, as well as between boards. It's wired up point to point, forming a logical grid (technically a 2D or 3D torus with wraparound links).