Reverse Engineering the Prom for the SGI O2(mattst88.com)
41 pointsby mattst883 hours ago4 comments
  • the_biota minute ago
    Awesome work! Enriching the disassembly with known constants and labels is great, great stuff.

    As somebody else suggested, try Ghidra's decompiler. It produces very sloppy C code, but still reads faster than assembly most of the time.

    Now enriching Ghidra's decompiler output to clean up the C code, that would be a neat trick, and one that Ghidra isn't doing.

  • userbinator3 hours ago
    In the PC world this would be known as "BIOS modding".

    The first two instructions looked legitimate, but the third looked unlikely to be a real instruction.

    Given that the first appears to be a branch, that's not surprising. When disassembling, not following the flow will likely not give you anything meaningful. If the author is reading this: have you tried Ghidra?

    That said, this seems a lot simpler than PC BIOSes in structure, as the latter are usually written in a combination of C and Asm (I can see why no one wanted to write MIPS Asm) and are self-extracting compressed archives.

  • nebula88043 hours ago
    I often see superbly restored SGI equipment at VCF and also own a few SGI equipment that I hope to get to some point in my life but I have never seen any interesting new software or usage of these machines other than the stock "cool" demo programs(The file manager, the gears demo and others running at the same time). Is there any actual cool homebrew occuring on these platforms?
    • tyfighter2 hours ago
      I think the lack of a real usable emulator for SGIs is holding back any kind of homebrew. I say this as one of the developer's that got SGI Indy emulation working in MAME. Yes, it works, but it's too slow and too old to be usable. I spent some time after the MAME effort working on a custom high performance emulator for Crimson/Onyx/Reality Engine, but I've kind of burned out again. Maybe some day if I'm really driven again, and had help. I've done most of the reverse engineering already, it's just a lot of code.

      I think that if a high performance, usable emulator for some of the big systems existed I think some of the old software might be rediscovered and show up on the internet.

    • spijdar2 hours ago
      Yes! I don't use my O2 a lot (I think the PSU is flaky, and I'm not super interested in IRIX), but I'm aware of at least https://forums.sgi.sh/index.php, among other similar sites, full of people porting/developing software for IRIX. It's a pretty active community for a 90s workstation platform, the most active one I'm aware of!
    • foldor2 hours ago
      I'm not aware of any cool homebrew, but there is a certain level of cool being able to compile the code for some N64 games using the original IDO compiler on original hardware. You can even compile one of the many decompiled games like Super Mario 64, Banjo Kazooie and more that all will produce the exact binary shipped on the cartridge byte for byte, all from reverse engineered work to create byte matching equivalent C code.
    • jrmcauliffean hour ago
      The main watering hole for the hobbyist community around these machines vanished from the internet a while back, taking the forums and info around porting software with it.. I guess some of it is available via wayback etc.
  • hinkleyan hour ago
    Oh, the PROM, not the prom.
    • mattst8825 minutes ago
      Yes, I submitted it as "PROM". I have no idea why it has been changed.