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  • ProDOS-86, yet another stupid Apple ][-related idea that will probably

    From Steve Nickolas@21:1/5 to All on Thu Oct 14 13:37:03 2021
    Several years ago, I thought of the idea of implementing ProDOS on some
    machine other than an Apple ][. I know it's stupid, insane and useless,
    but I decided to make ProDOS on an XT a thing, after some experience with
    my Tandy 1000HX about 20 years ago.

    Currently, I'm still at a complete loss of direction, but I did manage to
    write an IPL for it, i.e., a bootloader that can load a kernel file off a
    disk. Of course, it's NASM code for an 8086. I haven't even tried to
    make a "diglot" boot sector the way I do on an Apple ///.

    http://6.buric.co/p86head.a86.txt

    -uso.

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  • From qkumba@21:1/5 to All on Thu Oct 14 20:08:12 2021
    The interleave exists to avoid the "TXA / ASL / TAX" thing for doubling an index.
    You don't need the "add di, 0x100 / sub di, 0x00ff" stuff. You can "mov ah, [cs:di+0x100] / inc di".

    --- SoupGate-Win32 v1.05
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  • From Steve Nickolas@21:1/5 to qkumba on Fri Oct 15 00:07:02 2021
    On Thu, 14 Oct 2021, qkumba wrote:

    The interleave exists to avoid the "TXA / ASL / TAX" thing for doubling an index.
    You don't need the "add di, 0x100 / sub di, 0x00ff" stuff. You can "mov ah, [cs:di+0x100] / inc di".


    You can tell I don't speak fluent x86. This is definitely a 6502-flavored
    8086 ASM, for the most part.

    The next thing I need to do is figure out the "device issue" in a way that makes it look like an Apple ][ (e.g., A: as device 6).

    By making some tweaks to the floppy bootloader I went from being able to
    load about 32K (which is probably more than enough, given the size of
    ProDOS-8 2.0.3) to theoretically being able to load 128K, which would
    almost be big enough to run the later versions of MS-DOS. Better safe
    than sorry...

    -uso.

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