A key objective of RISC-V was that every aspect of the ISA must be based on an expired patent. It was felt that this is the only truly reliable defense against patent lawsuits.

It is surprising that patents would cover architecture as opposed to implementation. Or rather, would be surprising if one had not seen even worse examples over the last couple of decades.

What aspects of microprocessor instruction set architecture (as opposed to implementation) have been patented? Including patents which have now expired.

I know some relatively recent CPUs have included hardware support for various compression and cryptography algorithms, which are patented. The intent of this question is to leave those out, and focus on things that could reasonably be considered part of a general-purpose instruction set.

I'm also, in this context, not so much focused on the mainframe computers of the 50s and 60s, as on microprocessors, since their invention in the early 70s.

  • 1
    I think the list would be nearly infinite. For instance, browsing patents.justia.com/company/intel?list=patents, I counted at least five ISA-related patents granted to Intel in the past week. Feb 11 at 17:00
  • You could focus the question on patents from the retrocomputing era (say through 1985), and on those which had some significant impact on the industry, but it's still quite broad. Feb 11 at 18:20
  • @NateEldredge That is a lot of patents, indeed! However, looking over the first page of that, I don't see any ISA-related ones, except those that fall into the category I explicitly excluded, of 'take a specialized algorithm, provide a hardware accelerator for it'. But yes, I'm primarily interested in the early 70s to early 90s, before the Wintel steamroller really got going.
    – rwallace
    Feb 11 at 21:38


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