I should point out that I'm in no way advocating a WOS like approach, which given my numerous references to it in this thread, people might think. The only reason I mention it at all is that it serves as a demonstration that general multiprocessing (ie two processors that can run code simultaneously, rather than one processor and a custom chip or FPU etc) already has a precedent of sorts.
True SMP is a different beast all together, of course.