Can we consider higher-dimensional interconnect ?

Hypercube has lowest diameter for number of customers.

Chips are two-dimensional so perhaps 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.

Flattened butterfly : a cost-efficient topology for high-radix networks. John Kim, William J. Dally, Dennis Abts

(C) 2008-10, DJ Greaves, University of Cambridge, Computer Laboratory.