i guess cyrix and them didn't pay intel anything. it is open in the sense that anyone can attempt to make a compatible processor, i guess, and they can even try to extend the set (the mx instructions, not mmx, come to mind). not open like linux is, though. of course, its a little harder to produce a microprocessor than a linux dist. a lot of the later bits of x86 aren't open, like mmx, sse and sse2, and the supporting hardware signalling isn't either (gtl+) so not just anyone can make a chipset.