Usually replacing software with dedicated hardware tends to speed things up and I don't think it's obvious that using explicit communication would actually spee

Usually replacing software with dedicated hardware tends to speed things up and I don't think it's obvious that using explicit communication would actually speed things up. Most memory operations don't require any form of sharing and having the sharing that's required happen automatically seems efficient. Getting rid of virtual memory is potentially a big win, especially for architectures where you can't make the L1D cache virtually indexed but physically tagged. And in general there are a lot of special cases you don't even have to think about if different memory addresses can't alias to the same memory. You do lose out on a lot of software tricks there, though.