Scale-up topologies differ: Nvidia all-to-all vs Google torus

A scale-up domain is the tight set of chips communicating at terabytes/second; Nvidia's NVL72 connects 72 GPUs all-to-all, Google's TPU pods reach thousands of chips but use a torus topology where each chip connects only to six neighbors (requiring bounce-through with resource blocking), and Amazon sits between them—while all three are migrating toward dragonfly topologies that mix fully- and partially-connected elements.