Creating new CP/M disk from scratch

jim stephens jwstephens at
Fri Jun 2 21:03:46 CDT 2006

Richard A. Cini wrote:

>            I'm having trouble locating someone (anyone) who has a bootable
>5.25" single-density diskette suitable for my VersaFloppy controller. So, I
>was wondering the following. What if I setup an old PC with a 5.25" drive
>and use 22DISK to prepare a disk and move CP/M 2.2 .COM files to it from the
>PeeCee. Then, I would have to figure out how to get the cold-start loader
>onto the disk.

There was no official way supported in cpm to do this.

However in the brave new world of today, you can do it a variety of
ways, assuming:

22disk to write a floppy image

knowlege of the mapping of the file that 22disk uses.  assume
that the first 256 bytes = sector 0, the boot.

use a cpm emulator to build your bios and so forth.

this should result in two files on the cpm emulator, one
which has the boot sector, and one larger one with
the bios image.

move these out to files on the dos file system.

Use the method of you choice to merge the boot and
bios images together, taking care to maintain the sector
padding.  that is if you have a 50 byte boot file, pad
it out to 256, likewise round the length of the bios file
up, and determine how many sectors it takes.

Now determine where the boot is reading the boot
from, either sectors following the boot sector on track0,
or whatever.

I would paste together the image of at least track 0,
and have it prepared in a file.

The slice off that amount from your system boot disk
image from the front, and merge these together.

you can use something as simple as the linux dd
command to slice and dice, or the hex editor of
choice if you have another preference.

I have sliced and diced like this, but not for probably
10 years, and with considerably less recsources than I
have today.


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