> "Intel naturally tries to threaten and extend patents as much as they can. But they ISA itself can't be patented." It is practically impossible to implement

> "Intel naturally tries to threaten and extend patents as much as they can. But they ISA itself can't be patented." It is practically impossible to implement these extensions, such as SSE variants, without intel being able to make a case against you. So even if theoretically the ISA can't be patented, for all practical purposes they have the legal power to effectively prohibit a 3rd-party from implementing an x86 core.