Re: Software for MS-DOS 1.25

From: Michał Pleban <>
Date: Fri, 06 Oct 2017 17:35:34 +0200
Message-ID: <>

Steve Gray wrote:

> 1) How important is the MS-DOS version compared to the BIOS on the 8088
> card?

MS-DOS 1.25 is an "non-IBM OEM release", intended for computers that
were not PC-compatible. That means every computer manufacturer
customized it to their hardware. Therefore Commodore MS-DOS 1.25 will be
different from other variants of MS-DOS 1.25, even though the version
number is the same. You can only run the Commodore variant on the card,
as it is tailored to the hardware.

> 2) Did Commodore implement a complete BIOS on the card? If not, what is
> missing?

If you mean something like a PC-compatible BIOS, then the answer is no.

The EPROM on the card contains only an interface code to call the 6509
processor. There is code on the 6509 side which perform all the I/O
operations - you can call it a "BIOS" but it works very differently than
BIOS in a PC (the routines are accessed via inter-processor calls).

> 3) Is the MS-DOS 1.25 a "standard" release or is it customized for the BIOS?

As I said above, it is customized to the hardware (not just the BIOS).

> 4) If it's standard then what's stopping us from transferring newer
> MS-DOS releases?

Theoretically you could port different versions of MS-DOS if you wrote a
new IO.SYS file for them to interface with the Commodore hardware (and
most likely the 6509 code for it), but I don't think this is feasible.

> 5) Is there some standard PC test suite that can to a compatibility
> report of some kind?

The computer is NOT PC-compatible. That's the biggest problem with using
old MS-DOS software, which often assumes the computer is a PC.

> I'm willing to host disk images on my CBM-II webpages if you can
> assemble a nice collection of software verified working on the card.

Great, when I find some software that works I will gladly send it to you.

> Does RECV.EXE also send the files or is there a separate program for
> that? 

No, there is no mechanism for sending files. Maybe there is some MS-DOS
transfer software that could be downloaded, but originally RECV.EXE can
only receive files.

> Would it/they work using a USB to RS-232 converter?

If the RS-232 port is visible via a COMx handle, it should work. My
laptop has a standard COM port so I don't use any USB converte.


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Received on 2017-10-06 16:02:14

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