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Decompiling the Reference Diskette and associated programs

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Friends,

One of the major annoyances with using genuine IBM PS/2s (or even
emulated ones) is dealing with the Reference Diskette. I decided to
tackle this by first taking an inventory of what, exactly, the Reference
Diskette even is, what it does, and what the various programs on it do,
with a goal towards eventually replacing it with a far more compact
program, a much more compact representation of ADFs, and an ability to
run from things other than a diskette (such as a ROM BIOS, or, in the
most extreme cases, something hand-typed into ROM BASIC). Part of the
goal here is to make a PS/2 usable when it does not have a usable
diskette drive; currently, the only other way to set up such a system is
to perform RIPL from a Token Ring card.

I decided to start my focus on the Type 2 PS/2 Model 80, since (a) I
have the most personal experience with that machine's hardware, its
BIOS, and its ABIOS; and (b) it has some of the most thorough emulation
in 86Box. The Mod 50/60 has some problems in 86Box (relating to memory
sizing), and the Type 1 and Type 3 aren't 100% accurate.

So far I have found version 1.06 and 1.21 of the Reference Diskette. (My
Type 2 machine came with 1.21 back in the day, but that really just
meant that I went to the library at the local IBM office and pulled one
of the hundreds of Guides to Operations off of the shelf and ended up
with that version.)

Some preliminary analysis so far:

1.06 is byte for byte identical to PC-DOS 3.30. That's going to motivate
me to work on analysing the 1.06 refdisk first, since I don't have to
worry about DOS being different in some subtle way. (1.06 had the cute
"tutorial" on it, complete with pixel art of a Mod. 70 and 80 chassis.)

1.21 is a bit odder. It has a PC-DOS revision that is newer than 4.01:
it has some bugs fixed regarding printer handling and supports multiple
EMM modes. It definitely contains code that is not in the MS-DOS 4.01
source release. The DOS on it will be worthy of future analysis just to
figure out what it is, because it's not PC-DOS 5.00 either, and it's not
Multitasking MS-DOS 4. Maybe some OS/2 expert can tell me if there was
ever an "oddball" DOS found in an OS/2 beta release.

On a different topic... how hard is burning a PROM set (well, EEPROM
these days) for a PS/2? The end goal here is to eventually cram a
reference diskette inside the ROM.

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Thread

Decompiling the Reference Diskette and associated programs "Josh Rodd" <joshua.at.rodd.dot.us@rodd.us> - 2026-07-30 17:57 +0000
  Take me to the PROM Re: Decompiling the Reference Diskette and associated programs Louis Ohland <ohland@charter.net> - 2026-07-30 20:07 -0500
  Re: Decompiling the Reference Diskette and associated programs Kevin Bowling <kevin.bowling@kev009.com> - 2026-07-30 19:59 -0700
    Interesting Re: Decompiling the Reference Diskette and associated programs Louis Ohland <ohland@charter.net> - 2026-07-30 23:53 -0500
      Catching the Night Train Re: Interesting Re: Decompiling the Reference Diskette and associated programs Louis Ohland <ohland@charter.net> - 2026-07-30 23:58 -0500
      Re: Interesting Re: Decompiling the Reference Diskette and associated programs Kevin Bowling <kevin.bowling@kev009.com> - 2026-07-30 23:08 -0700
        Re: Interesting Re: Decompiling the Reference Diskette and associated programs Louis Ohland <ohland@charter.net> - 2026-07-31 08:26 -0500
          Re: Interesting Re: Decompiling the Reference Diskette and associated programs Kevin Bowling <kevin.bowling@kev009.com> - 2026-07-31 10:41 -0700

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