ROM-MJS is a suite of programs designed for Z80 based systems to assist in debugging hardware and installing CP/M software.

Included in the package are the following applications:

  • Basic debug monitor. Designed for small ROM environments. Includes some basic diagnostic testing of hardware and code to load a boot file from disk.
  • Extended debug monitor. Designed for hardware debugging and software installation. Supports booting an operating system image stored on a disk partition.
  • BIOS and XIOS for CP/M (2.2 and 3) as well as MP/M.
  • Utility programs for managing CP/M disk partitions, copying files from a FAT volume and installing boot code to a partition.

Depending on the available ROM in the system, the Basic or Extended Monitor is loaded into ROM and executed at reset/power-on.

The basic monitor is capable of loading the Extended Monitor from disk if required.

ROM-MJS supports PC style partitions (MBR) allowing the use of up to 4 PRIMARY partitions. Disks can be partitioned using any disk partitioning software providing that the partitions created are PRIMARY partitions and of type 0x52 (CP/M). CP/M partitions can be 8MB or larger. However, currently the BIOS and XIOS only support 8MB disks.

The extended monitor supports READ-Only access to a FAT16 or FAT32 partition and can load files into RAM, copy disk images directly to disk (sector copy) and run utility applications without booting CP/M.

The various hardware drivers are combined into a Hardware Access Layer which provides a standard API for the monitor as well as the CP/M 2 BIOS to access. This allows a system disk to be moved between multiple systems and booted without needing a different BIOS for differing hardware. Some CP/M utilities talk directly to the Hardware Access Layer to manipulate the environment underneath the operating system.


The following implementations are available:

Implementation Current Version Date
ROM-MJS for Multicomp 1.5.1 2016/1/4



FilenameFilesizeLast modified
cpm2-install_guide.pdf54.0 KiB2015/12/16 16:09
disk_preparation_guide.pdf1.1 MiB2015/12/16 05:04
rom-mjs_utility_guide.pdf125.0 KiB2016/07/19 07:53
setting_up_auto_boot.pdf444.7 KiB2015/12/28 18:59

Cross Platform Software Images:

FilenameFilesizeLast modified
cpm2-img.bin168.2 KiB2016/01/04 01:38

Note: The CP/M 2.2 image is a universal image and will boot on any ROM-MJS implementation

software/firmwareos/rom-mjs/start.txt · Last modified: 2016/12/15 21:13 by mscane
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