There are ancient design decisions regarding exclusive locks. Early on, while it was a bus, it just used a signal for "locked" (~a mutex), and later this physic

There are ancient design decisions regarding exclusive locks. Early on, while it was a bus, it just used a signal for "locked" (~a mutex), and later this physical broadcast had to go because the interconnect switched to a fabric of point-to-point SerDes links. The remote atomics are a GPU-independent feature on the SMP interconnect. The GPU thing is mostly icing on the cake, by exposing this feature to NVLink GPUs (iirc. Volta+, maybe Pascal+).