CP/M Support

Included with Idun is this repositorythat contains CPem; a modified version of the excellent "RunCPM" emulator by Marcelo Dantas. CPem has been improved to work with the idun-cartridge and to support the real z80 CPU when running programs on a Commodore 128.

Getting Started

You can launch directly into CPem from the Idun shell or BASIC prompt using the command go "cpm". Once started, you will be in a CP/M v2.2 compatible OS that can run "vanilla" CP/M text programs. The environment is emulated on the Raspberry Pi's ARM processor, so CP/M programs run super fast. You can use all the standard CP/M commands, plus some additional built-in commands. To see the built-in commands, enter ?. To see what CP/M software is available, you can enter drives to get a list of disk drives, then enter vol a:, vol b:, etc. to see what is on each drive. You can switch to drive B, for example, by entering b: and to user area 1 by entering either user 1 or b1:.

The terminal is VT-100 compatible. Therefore, CP/M programs that are setup to use VT-100 will work best. If you have weird looking text output from a CP/M program, you should investigate what kind of terminal it is setup to use. CP/M software compatibility problems that can be improved by modifying the CP/M software, its setup, or the idun-cartridge VT-100 emulation abilities can be reported here using GitHub's "Issues" reporting.

Running programs on real Z80

If you are using the idun-cartridge on a Commodore 128, then you have the best of both worlds- fast, emulated performance along with the ability to launch (and develop!) programs on the C128's Z80 CPU. CPem's command processor will assume that any command with a ".Z80" extension is a native program intended to run on the C128. Such programs are identical to the programs also supported by the zload command used to launch them from Idun shell. These programs are most easily created using the ZCC cross-compiler from idun-zcc. Some sample programs are available on drive c1:.

Development Tools

CP/M might be best remembered for the large selection of software development tools it offered. Default drive A0: includes Z80 assemblers and mbasic. Other drives include C, Pascal, and BASIC compilers. Plus there is BBCBASIC and a Forth language compiler. All of these CP/M dev tools run very fast and can thus provide an enjoyable way to learn as much as you ever wanted to know about CP/M programming.

The ZCC cross-compiler that is also installed on the idun-cartridge can build both native c128 and CP/M programs. ZCC is based on the excellent Z88DK project. It has an extensive library and provides a more "modern" C programming experience.

Access CPem remotely

This package also creates a cpm user account. The reason this account exists is to turn the idun-cartridge into a remote CP/M terminal that you can access from your PC using ssh. Just login using ssh cpm@idunpi.local (default password idun). This user account drops you directly into CPem. You can leave the cartridge powered up by an external USB power supply, and then use CP/M this way with your Commodore turned off.

Future possibilities...

BIOS extensions and/or driver libraries to allow CP/M programs running on the emulated (accelerated) Z80 to directly access the Commodore's VIC-II or VDC to display text and graphics.