Comment by jeffbee

AMD's NPS4 mode isn't exactly user-friendly, I agree. But you can put it into NPS1 mode and relax. Graviton 5, as a counterpoint, doesn't give you the option. Physically there is a 2D mesh between the cores and the memory controller but the observable behavior is that every access gets the average mesh fabric latency. The efficiency you leave on the table isn't very large, whereas in multisocket NUMA you can't ignore the cost.

I think you can over-analyze this stuff and lose your sanity. On these multicore systems there are also hot cores in the center of the mesh and cold ones at the edges and theoretically you could be doing temperature-aware scheduling, gaining a bit more efficiency in doing so. But it's just easier to adopt the black box model of spherical frictionless CPUs.