IANAL, but yes, ISA extensions can be patented. For example, the x86-64 extension ("Long Mode") was created by AMD, and Intel had to pay to license it.[0] Those

IANAL, but yes, ISA extensions can be patented. For example, the x86-64 extension ("Long Mode") was created by AMD, and Intel had to pay to license it.[0] Those patents expired a few years ago, allowing Microsoft and Apple to write x86-64 to ARM translators freely. [0]: https://en.wikipedia.org/wiki/X86-64#Licensing https://en.wikipedia.org/wiki/X86-64#Licensing