I think this is primarily about backwards compatibility. New CPUs, especially from Intel, were about running existing software faster. The shared memory parad

I think this is primarily about backwards compatibility. New CPUs, especially from Intel, were about running existing software faster. The shared memory paradigm goes back to single core (and mainframes) and is pervasive, in code, in languages, in libraries. It's really hard to rewrite all the software on this planet to use some channel mechanism between cores and that also makes it tricky when the OS needs to schedule threads. I think there were some historical examples of this sort of architecture (Transputers?) and generally they didn't fare that well... If you made a new CPU where there's no shared memory between cores I'm not quite sure who would use it. It's also not that clear how much simpler it makes things on the chip and for the developers.