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    This processor is one of my favorite terrible ideas.

    It’s a terrible idea because they didn’t talk to the compiler team until after they’d taped out the core so they ended up with a bunch of common operations requiring 200 or more cycles. Several things ended up being indirection tables that meant that even an optimised follow-on improved microarchitecture would still have been slow.

    My favourite, because it was fully memory safe and capability-safe hardware, in the early ‘80s. This is basically solving the same problems that I am, just 40 years earlier. A lot of what we did in the CHERI project was explicitly not what the 432 did, because it explored a lot of the design space of things that don’t work.

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      There is a really fun book about the Rekursiv computer that was built by some random audio company in the UK in the 80s. They were trying to make hardware to run a Smalltalk-like system. The book itself is a really good overview of the architecture, as well as having its fair share of smart-assery. In the end, it looks like one of these computers ended up in the bottom of a canal somewhere.

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        Linn. They’re still around.


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          The Mushroom project at Manchester in the ’80s also tried to build a computer for Smalltalk. They had hardware-assisted GC and a bunch of other interesting features, prototyped across 7 FPGAs. Some of the same folks ended up working at Sun on Project Maxwell, which almost added GC support to SPARC before being cancelled (their approach was really neat: hardware young-generation compacting in the cache, barriers to allow old-generation compacting in software to be efficient). Reading a bit about the Rekursiv computer, I wonder if any of the same folks were involved: some of the concepts resurfaced in Maxwell…

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        I’ve always loved this architecture.

        I’m surprised that there doesn’t seem to be an emulator anywhere, nor even an effort for one.

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          There are a number of capability systems that are basically gone into the mists of time. I was hoping to persuade someone to write an emulator for the Cambridge CAP Computer before all of the folks that worked on it died. I think someone found a printout of the system software a few years ago.

          An FPGA 432 would be a fun student project if the data sheets or software existed.

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            I think because the data sheets for this don’t exist, and what’s out there isn’t enough to go by to implement an emulator.