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MS-DOS runs on Apple IIe

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You need to add an 8088 coprocessor card to your Apple, but the result is
that MS-DOS and "a lot of off-the-shelf DOS software just works."

Seth Kushniryk writes:
Two weeks ago I posted about getting MS-DOS 2.0 to boot on the AD8088 Plus
coprocessor card. Since then I’ve been working on getting it into a
publishable state, and today it’s ready.

The source is at git.sr.ht/~sethkush/reboot-camp-83. Everything you need to
build and run MS-DOS 2.0 on an Apple II with an AD8088 card is in the
repository — the full MS-DOS 2.0 kernel source (MIT licensed by Microsoft),
the OEM BIOS, the 6502 bridge, build scripts, and a bunch of ported DOS
software.

The first post covered the initial boot. Since then the bridge — the 6502
program that mediates between the 8088 and the Apple II — was relocated from
$0C00 to $0800, freeing up both HGR pages ($2000-$5FFF) for programs that
want to draw to the Apple II’s hi-res screen. This was harder than it
sounds. The relocation exposed a cascade of buffer overlap bugs between the
staging area, ProDOS I/O buffers, and the ROM copy timing. I also hit an
undocumented ProDOS constraint where MLI READ limits the request count to
the distance between your data buffer and the nearest internal file buffer
above it in memory. That one took a while.

The bridge now handles INT 10h video BIOS, INT 16h keyboard BIOS, and an
ANSI escape sequence parser in the CON driver. Open Apple acts as Meta/ESC,
and Closed Apple maps to function and navigation keys (F1-F12, Home, End,
PgUp, PgDn, Insert, Delete). The cursor blinks in sync with the Apple II’s
VBL.


You need an Apple II with an 80-column card, an AD8088 or AD8088 Plus
coprocessor, and a ProDOS-compatible mass storage device (CF card, SD card,
SCSI drive). Copy the output image to your storage, boot ProDOS, and select
MS-DOS from the startup menu.

Read the whole article, with screenshots:
https://sethkush.com/post/2026/03/22/reboot-camp-83-ms-dos-on-the-apple-iie-is-ready/

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MS-DOS runs on Apple IIe D Finnigan <dog_cow@macgui.com> - 2026-03-30 19:12 +0000
  Re: MS-DOS runs on Apple IIe D Finnigan <dog_cow@macgui.com> - 2026-03-30 19:14 +0000
  Re: MS-DOS runs on Apple IIe Steve Nickolas <usotsuki@buric.co> - 2026-03-31 17:08 -0400
    Re: MS-DOS runs on Apple IIe D Finnigan <dog_cow@macgui.com> - 2026-04-01 12:37 +0000
      Re: MS-DOS runs on Apple IIe Steve Nickolas <usotsuki@buric.co> - 2026-04-02 20:03 -0400

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