Yes, though that's a different formulation of (2) really: > Nobody else but Apple has the right to have these ISA extensions Programmers "can" use Apple exten

Yes, though that's a different formulation of (2) really: > Nobody else but Apple has the right to have these ISA extensions Programmers "can" use Apple extensions because... they're extensions to the ISA, they're not documented but they can't really be blocked off unless they're ring0, and that would make them a lot less useful (the entire point of having extensions for matrix computation is to speed up matrix computations, which are not usually kernel work, and having to syscall to do them would waste the entire thing).