xbeaver (A Nascom and Gemini 80 bus emulator)

Beaver Booting xbeaver is a 80bus (nascom, gemini and others) emulator. It runs on a linux system (under curses and X).

The 80bus is a microprocessor bus standard which is derived from the Z80 microprocessor bus. Several companies produced boards for this bus which was quite popular in the UK.

xbeaver supports emulation of a considerable number of these boards and this allows many different system configurations to be emulated by combining different board combinations into a system. Several configurations are included in the download - each configuration being specified by a configuration file. The user is free to create their own configurations as desired.

New boards can be implemented by any C programmer by following these guidence notes. Please send the source code for any new boards implemented to . This address can also be used to send ideas for improvements and bug reports.

The code and pre-compiled Binary (tar file) is available for download as xbeaver.tgz. Both are released under the GNU License.

This documentation pack can be downloaded as xbeaver_documentation.tgz for local reference. Also released under the GNU License.


xbeaver -h gives help on the command line arguments. The following arguments are permitted:-

Driving Physical Hardware

xbeaver can access real hardware. This can be achieved in one of several ways:-

  1. By using an emulated serial port and associating it with a physical serial (eg RS232) port.
  2. By using the pptbus board which uses /dev/parportN and custom hardware to generate a microprocessor style bus.
  3. By using the extbus board to access hardware. This is used in a similar manner to /dev/port where the file position dictates the io port to be accessed.

Note:- As for any device - the permissions must be set to allow access.

There is also an optional linux device driver z80xbus.tgz which uses the file position technique and same custom hardware mentioned above to generate a microprocessor style bus.

Operating Systems Supported

Several operating systems are available for the xbeaver system.

For full details of the 80 bus system see www.80bus.co.uk or a mirror of the site at https://80bus.co.uk.mirror.jloh.de/

Other machines emulated

The xbeaver system is now capable of emulating:-

  1. The Intel Intellec MDS-800 (This is the original machine CP/M was developed for) - see operating systems for details on how to run ISIS (The original MDS operating system).
  2. The Triumph Adler Alphatronic (Matmos PC)
  3. The NorthStar Advantage

Software Collection

A collection of software for real/emulated machines (mostly z80) is available for download.