What Operating System Has Crashed Here?

(Read comments for solution.)

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30 Responses to “What Operating System Has Crashed Here?”

  1. Darkstar says:

    Judging from the register set (D0-D7, A0-A7, SR) I’d say it’s an 68000 CPU. This also fits with the “level 7 interrupt” error.
    So it’s probably either Apple or Amiga. Google is a bit lacking here, so my bet is either A/UX (on the 68020) or Amiga UNIX (on the 68030)


  2. kerobaros says:

    That looks a lot like a Commodore typeface. Is that Amiga?

  3. Dennis says:

    Gonna go out on a limb here and say it was the Apple Lisa.

  4. tramms says:

    the most crazy I can think of: Xenix/68000 on Apple Lisa — just a guess ;-)

  5. Darren says:

    My first guess is some sort of Unix running on a Vic-20. Since that’s ridiculous, the next closest guess is the Amiga.

    I understand there was a version of Unix for Amiga at one time.

  6. 720×364 is the resolution of the Lisa so that makes sense. The font looks different to the one you see when starting the Lisa and by the Workshop (there’s more of a tail on the t). I found the LisaBug docs that have the same format, so it looks like that’s it…

  7. Damien Guard says:

    That’s not an Amiga font – it’s almost identical to Commodore PET though.


  8. Damien Guard says:

    Good find Nicholas – that documentation even has the Level 7 message so it’s definitely the Lisa.

    Very interesting that the Apple Lisa ripped off the Commodore PET system font…


  9. Darkstar says:

    There are only so many ways to create a readable 8×8 bitmap font, so it might actually be a coincidence that the font looks like the PET font


  10. Robert says:

    It may be an OS running on an Amiga, but it’s not the AmigaOS. AmigaOS does not use this system font, nor does it trap the level 7 interrupt, nor does its internal debugger have a visual interface (it communicates entirely over the serial port).

  11. Damien Guard says:

    There are a LOT of ways to create an 8×8 bitmap font – I covered some of the system fonts http://damieng.com/blog/2011/03/27/typography-in-16-bits-system-fonts and http://damieng.com/blog/2011/02/20/typography-in-8-bits-system-fonts and it is actually as far as I can tell a direct rip of the PET font.


  12. Tom says:


  13. Bobg says:

    Wild guess: Amiga NetBSD?

  14. Joe Z says:


    Yes, it does appear to be the PET font, which is a weird choice. You can see some of the peculiarities in the 2, 5 and 7 are identical between the two.

    A minor quibble on your typography page: The TMS-9918 VDP doesn’t have a built in font or even a default font ROM, since it’s entirely “soft:” everything comes from RAM. And FWIW, the PPU in the NES is a different beast from the VDP.


  15. retroK says:

    So the only question remaining is, what caused the crash?

  16. Damien Guard says:

    The TMS-9918 VDP datasheet at http://www.cs.columbia.edu/~sedwards/papers/TMS9918.pdf certainly documents a bitmap font toward the end.


  17. dex says:

    See page A-1 of the document: “Software programs apply to all three VDPs”.
    Then see page 4-6 and 4-9 to 4-15.
    VDP uses an external font generator.

  18. Andrea says:

    Amiga BSD

  19. dwhuseby says:

    I agree with darkstar, my guess is A/UX on a 68k mac.

  20. Mattias says:

    It’s probably not a 68020, ’030 or ’040 – they have two supervisor stack pointers (although it is possible that the crash dump would only show one of them).
    It’s not a ’008 either, because the PC has too many bits in it.
    Oddly, SR indicates that it’s in user mode, but that does not necessarily mean anything.

  21. dwhuseby says:

    Could this be a MiNT crash on an Atari machine? Just a thought.

  22. Peter Gordon says:

    Easy peasy. QDOS.

  23. [...] pagetable.com comes this mysterious crash screen. Click through the image above for the original post and [...]

  24. SSquire says:

    More importantly, has anyone tried turning it off and back on again?

  25. Johan says:

    Looks like a 68000 system. Pre 68020 since all addresses are in the 24 bit range.
    The program counter is in the 0x2e memory block and the stack pointer (a7) is in the 0xf7 memory block.
    Both these places probably has ram.

    On the Amiga, 0x2e is in the Fast ram (expansion) area, so thats good, but 0xf7 is in the system rom. So its probably not Amiga hardware.

    On the Atari ST, 0x2e is in the expansion ram area, and 0xf7 is in an unmapped memory area. So probably not Atari ST, unless its a action replay like device.

    Its not a TI-89. http://education.ti.com/downloads/guidebooks/sdk/89/sdk8992pguide.pdf

    Its not a x68000. http://www.jcec.co.uk/X68kinfo.html

    Could not find any memory layout docs for Lisa, Old Macintosh or 68K sun.

  26. Johan says:

    Its probably Microsoft Xenix running on one of it’s supported 68000 platforms, probably Apple Lisa but it could be the Alto.

    The font is the same and everything.

    Here is instructions on how to run the emulator yourself.

  27. iDG says:

    I am the only one that feels a little bit of discomfort in noticing that there are THREE cursors in the image?

  28. Clovis says:

    This is Microsoft Bob(tm)(r)(c).

    The BRA at the top means Bob Ran Away, hence the crash – Bob is the world, so without Bob there is no world, just grey with funny letters and numbers; level 7 refers to the Microsoft senior management grade – one of them came looking for Bob to make his mail-thing work again (he’s forgotten about having to click something to send the email again. Silly Microsoft senior manager).

    Where do I collect my prize from?

  29. Michael Steil says:

    Excellent work everyone! It is indeed the Apple Lisa (68K), and it’s the standard Lisa operating system.

    The prize goes to Nicholas Riley for analyzing the screen size and proving it with another screenshot, second class prizes to Darkstar for recognizing the 68K first, Johan for the very detailed analysis, and Clovis for the very creative answer!

    @Damien Guard: Great work on those fonts! We’ve extracted tree fonts from the Lisa here; I’ll post them some time…

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