Can we consider higher-dimensional interconnect (non examinable) ?
The hypercube has lowest diameter for number of customers.
Chips are two-dimensional so perhaps it's good to use a 2-D network ?
Maybe use 2.5-D ? have a small number of `multi-hop' links?
On benign (load-balanced) traffic, the flattened butterfly approaches the cost/performance of a butterfly network and has roughly half the cost of a comparable performance clos network.
The advantage over the clos is achieved by eliminating redundant hops when they are not needed for load balance.
See `Flattened butterfly : a cost-efficient topology for high-radix networks' by John Kim, William J. Dally, Dennis Abts.