I'm studying ISAs and would really like to see the very first ISA that Sophie Wilson chose/put together when designing the very first ARM CPU while at Acorn Computers around 1983 or so.

From what I understand, they (she and Steve Furber) collaborated and chose the ideal instruction set for their planned processor, using the RISC paradigm they recently learned about.

Does anyone know of a copy of this instruction set (I would love to see Sophie Wilson's original design, before Steve Furber asked to cut out a few instructions that he felt weren't technically possible to physically fabricate)?

I've looked online and on various forums but couldn't find anything definitive. Maybe this was never published, but there must be some historical record?

It could just be a high-level overview: number of instructions, brief description of what each instruction does. It doesn't have to be the technical (official) specification, though that would be great.

Thanks in advance.

  • 3
    arstechnica.com/gadgets/2022/09/… lists 45 instructions. Not sure if that is before or after pruning any out.
    – Jon Custer
    Commented May 12, 2023 at 16:43
  • 5
    AFAIK ARMv1 is the first published ISA, post-clean-up. Commented May 12, 2023 at 18:25
  • 9
    Sophie Wilson has a personal web page, with an e-mail address. If you want to know about pre-v1 ARM, I think your best bet is to ask her. Commented May 13, 2023 at 10:45
  • 4
    And if she responds, you might like to ask her for permission to provide the instruction set here in an answer, for those interested in it. Commented Jul 26, 2023 at 7:23
  • 2
    Please ask this on stardot.org.uk. They have many ex-Acorn people there, and have put together several events where Sophie talks CPU design. I don't think they've ever located the original ARM simulator code, though
    – scruss
    Commented Jul 26, 2023 at 15:38


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