I have decided to try out some old CP/M software, but need something to run it on.  I could either do this on my Commodore 128 or through emulation.  Unfortunately the 1571 disk drive for my Commodore is currently out of action, so that leaves me with emulation.  I was going to use vice to emulate a C128, but have always found it a pain to get CP/M files onto .D64/71 disk images.  After looking around for the best emulator to run CP/M on, I came up with either YAZE-AG or z80pack. z80pack seems to be better supported, has more documentation and is being actively developed, so that's the one I have chosen for this article.

Installing z80pack

  • First download the source (z80pack-x.y.tgz, currently z80pack-1.17.tgz) for z80 pack from here. The following installation instructions are taken from the z80pack site. More information can be found there, in particular, information on installing z80pack on non Linux/Unix systems.
  • Unpack the source archive in your home directory:
$ tar xzvf z80pack-x.y.tgz
  • Change the directory it is extracted to, to make this article easier to explain. There is no need for you to do this.
$ mv z80pack-1.16 z80pack
  • Compile the emulator:
   $ cd ~/z80pack/cpmsim/srcsim
   $ make
   $ make clean
  • Compile the support programs:
   $ cd ~/z80pack/cpmsim/srctools
   $ make
   $ make clean

This is leaves, on Linux, a few bash scripts in the ~/z80pack/cpmsim/ directory, cpm2, cpm3, mpm, which automatically start the emulator by booting into CP/M 2.2, CP/M 3.0, MP/M, etc.

Creating disk images

We now needed to create some disk images; to do this I recommend Cpmtools which is a part of many Linux distros. If you don’t have this as part of your distro, the source can be downloaded from here. Cpmtools is a great collection of tools used to manipulate CP/M images and file systems in a variety of formats and works well with z80pack.

Create a 4Mb Hard Disk Image

It would be useful to create a 4Mb Hard Disk Image, as this may be needed if we want to use any bigger applications such as a C compiler.  To create this we can use Cpmtools, but first we need to make sure that it has the correct disk definition by editing /etc/cpmtools/diskdefs and adding the following lines:

# 4mb HDD for z80pack
diskdef hd
  seclen 128
  tracks 255
  sectrk 128
  blocksize 2048
  maxdir 1024
  skew 0
  boottrk 0
  os 3.0
end

CP/M has 16 ‘user areas’ which can be used to organize data on a disk. They are effectively like a crude directory system. User area 0 is the default and the only one we will work with in this article.

To create a blank 4Mb Hard Disk image called main.hd4.cpm, run:

$ mkfs.cpm -fhd main.hd4.cpm

Then to copy all the .COM files from the current directory into the image in user area 0, run:

$ cpmcp -fhd hd4.cpm *.COM 0:

Create a Floppy Diskette Image

To create a floppy diskette image called, work.dsk.cpm, run:

$ mkfs.cpm work.dsk.cpm

Then to copy all the .DOC files from the current directory into the image in user area 0: run:

$ cpmcp work.dsk.cpm *.DOC 0:

Configuring z80pack

We now have a 4mb disk image and a floppy disk image. We can connect them to the emulator by creating a script in the ~/z80pack/cpmsim/ directory called work. First copy main.hd4.cpm and work.dsk.cpm to the ~z80pack/cpmsim/disks/library/ directory. It is also worth copying them to the backups directory as well: ~/z80pack/cpmsim/disks/backups/

Now create a script in ~/z80pack/cpmsim/ called work to start z80pack with our disk image files attached:

#!/bin/sh
rm -f disks/drive[abci].cpm
ln disks/library/cpm3-1.dsk disks/drivea.cpm
ln disks/library/cpm3-2.dsk disks/driveb.cpm
ln disks/library/work.dsk.cpm disks/drivec.cpm
ln disks/library/main.hd4.cpm disks/drivei.cpm
./cpmsim -f4

This attaches the two CP/M disks on drive A and B, our work.dsk.cpm image on drive C, and our main.hd4.cpm image on I: The line ./cpmsim -f4 tells the emulator to run at 4Mhz, which makes it a bit more realistic.

Starting the emulator

From the ~/z80pack/cpmsim/ directory, run the script we created:

$ ./work

The CP/M operating system will now boot up and leave you at the A> prompt.

To leave the emulator type:

A> a:bye