we built machines with all kinds of approach to this. ones with giant shared memories and memory networks. the tera MTA famously had uniform memory access, since all of the memories were on the other side of a network from the CPU, and hardware managed threads tried to hide that latency.

we built machines with RDMA that allowed fast one-sided transfers between memories at a decent fraction of the memory bandwidth. and operating systems that ran services to present a unified operating system interface on top of that.

there is a whole history of distributed operating systems if you're interested