There is often a quite significant distance between the beautiful, elegant and efficient design that brings tears to the eyes of a designer, and being pragmatic

There is often a quite significant distance between the beautiful, elegant and efficient design that brings tears to the eyes of a designer, and being pragmatic and financially viable. Building a new competitive processor architecture isn't feasible if you can't at least ensure compile-time compatibility with existing programs. People won't buy a processor that won't run their programs.