They use custom optical "Interchip Interconnect" within each 256-chip "pod" and their custom "Jupiter" networking between pods. See https://cloud.google.com/bl

They use custom optical "Interchip Interconnect" within each 256-chip "pod" and their custom "Jupiter" networking between pods. See https://cloud.google.com/blog/products/compute/introducing-trillium-6th-gen-tpus https://cloud.google.com/blog/products/compute/introducing-t... and https://cloud.google.com/blog/topics/systems/the-evolution-of-googles-jupiter-data-center-network?e=48754805 https://cloud.google.com/blog/topics/systems/the-evolution-o...