> machines with 2^n cores where each core has a direct data channel to every core with its n-bit core ID being one but different (plus one for all bits different).

NCube. 64 to 1024 CPUs in an N-dimensional cube.[1] I played with one a bit when Stanford got one surplus from an oil drilling company. Not very useful.

It's straightforward to build non-shared-memory MIMD machines, but they are not historically successes and are very difficult to program. Classic example: Sony PS3. Unless the problem is very well matched to the architecture, which we might see for backpropagation and such.

[1] https://ncube.systems/overview.html