Re: CP/M disks

From: Craig Taylor <>
Date: Sat, 3 Jun 2017 17:19:57 -0400
Message-ID: <>
For the 128 cpm 71 and 41 disks they're in GCR by default.  The 128 can
read MFM com disks but by default it's GCR.

If I remember right the directory information starts on track 1 instead of
18.  I forget how the user spaces are done.  Some disks have both track 18
and 1 populated for e.g. booting .

On Jun 3, 2017 3:02 PM, "Steve Gray" <> wrote:

If the CP/M virtual disk is in a PRG or SEQ file that can be read I would
be able to add a directory viewer to CBM-Transfer (aka cbmxfer). I don't
think the CP/M disk structure is too complicated.
However, if like the ones in your zip file, it uses a REL file then I won't
be able to (easily) support it. In such cases I think you could probably
find the CP/M directory sectors using a regular Hex Editor/Viewer.
CBM-Transfer has a hex viewer, which has options to view in a more
cbm-friendly format. Or, for windows I recommend the "HxD" editor.


*From:* "" <>
*Sent:* Saturday, June 3, 2017 6:34 AM
*Subject:* CP/M disks

Hallo allemaal,

First, the CP/M disks for the CBMs can be found here:

Then FYI: except starting up a boot disk or a program I didn't do
very much with CP/M on the C128. Therefore quite some lack of
knowledge. Please, bear with it :)

Three question:
- I more or less always thought that C128 CP/M disks were a mix of
Commodore's GCR format and one or another MFM format. But the first
disk I tried to create an image of turned out fine. Second disk, a
CP/M boot disk: fine as well. third disk, another boot disk: nope.
But as D64 it turned out fine as well. The question: what is normal?

- Is there a quick way to find out whether I'm dealing with a D64 or
a D71? I know tell the program to treat the disk as a D71. It first
reads track 1 and then 36. If that goes wrong I know enough. But the
time consuming part is Ctrl-C and resetting the ZF by removing and
reinserting the USB plug.

- Opencbm provides the tools for displaying the directory. But not
for CP/M disk AFAIk. Neither CbmXfer. Unless I overlooked something.
I have run and still run in various CP/M disks were the text on the
labels faded away. Is there a tool to see their director?

Many thanks in advance!


Kind regards / Met vriendelijke groet, Ruud Baltissen

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Received on 2017-06-03 22:00:03

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