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RomWBW ReadMe
Version 3.2
Wayne Warthen (
18 Mar 2023


RomWBW software provides a complete, commercial quality implementation of CP/M (and workalike) operating systems and applications for modern Z80/180/280 retro-computing hardware systems. A wide variety of platforms are supported including those produced by these developer communities:

General features include:

  • Banked memory services for several banking designs
  • Disk drivers for RAM, ROM, Floppy, IDE, CF, and SD
  • Serial drivers including UART (16550-like), ASCI, ACIA, SIO
  • Video drivers including TMS9918, SY6545, MOS8563, HD6445
  • Keyboard (PS/2) drivers via VT8242 or PPI interfaces
  • Real time clock drivers including DS1302, BQ4845
  • OSes: CP/M 2.2, ZSDOS, CP/M 3, NZ-COM, ZPM3, QPM, p-System, and FreeRTOS
  • Built-in VT-100 terminal emulation support

RomWBW is distributed as both source code and pre-built ROM and disk images. Some of the provided software can be launched directly from the ROM firmware itself:

  • System Monitor
  • Operating Systems (CP/M 2.2, ZSDOS)
  • ROM BASIC (Nascom BASIC and Tasty BASIC)
  • ROM Forth

A dynamic disk drive letter assignment mechanism allows mapping operating system drive letters to any available disk media. Additionally, mass storage devices (IDE Disk, CF Card, SD Card) support the use of multiple slices (up to 256 per device). Each slice contains a complete CP/M filesystem and can be mapped independently to any drive letter. This overcomes the inherent size limitations in legacy OSes and allows up to 2GB of accessible storage on a single device.

The pre-built ROM firmware images are generally suitable for most users. However, it is also very easy to modify and build custom ROM images that fully tailor the firmware to your specific preferences. All tools required to build custom ROM firmware under Windows are included – no need to install assemblers, etc. The firmware can also be built using Linux or MacOS after confirming a few standard tools have been installed.

Multiple disk images are provided in the distribution. Most disk images contain a complete, bootable, ready-to-run implementation of a specific operating system. A “combo” disk image contains multiple slices, each with a full operating system implementation. If you use this disk image, you can easily pick whichever operating system you want to boot without changing media.

By design, RomWBW isolates all of the hardware specific functions in the ROM chip itself. The ROM provides a hardware abstraction layer such that all of the operating systems and applications on a disk will run on any RomWBW-based system. To put it simply, you can take a disk (or CF/SD Card) and move it between systems transparently.

A tool is provided that allows you to access a FAT-12/16/32 filesystem. The FAT filesystem may be coresident on the same disk media as RomWBW slices or on stand-alone media. This makes exchanging files with modern OSes such as Windows, MacOS, and Linux very easy.

Acquiring RomWBW

The RomWBW Repository on GitHub is the official distribution location for all project source and documentation. The fully-built distribution releases are available on the RomWBW Releases Page of the repository. On this page, you will normally see a Development Snapshot as well as recent stable releases. Unless you have a specific reason, I suggest you stick to the most recent stable release. Expand the “Assets” drop-down for the release you want to download, then select the asset named The Package asset includes all pre-built ROM and Disk images as well as full source code. The other assets contain only source code and do not have the pre-built ROM or disk images.

All source code and distributions are maintained on GitHub. Code contributions are very welcome.

Installation & Operation

In general, installation of RomWBW on your platform is very simple. You just need to program your ROM with the correct ROM image from the RomWBW distribution. Subsequently, you can write disk images on your disk drives (IDE disk, CF Card, SD Card, etc.) which then provides even more functionality.

Complete instructions for installation and operation of RomWBW are found in the RomWBW User Guide.


Documentation for RomWBW includes:


I want to acknowledge that a great deal of the code and inspiration for RomWBW has been provided by or derived from the work of others in the RetroBrew Computers Community. I sincerely appreciate all of their contributions. The list below is probably missing many names – please let me know if I missed you!

  • Andrew Lynch started it all when he created the N8VEM Z80 SBC which became the first platform RomWBW supported. Some of his original code can still be found in RomWBW.

  • Dan Werner wrote much of the code from which RomWBW was originally derived and he has always been a great source of knowledge and advice.

  • Douglas Goodall contributed code, time, testing, and advice in “the early days”. He created an entire suite of application programs to enhance the use of RomWBW. Unfortunately, they have become unusable due to internal changes within RomWBW. As of RomWBW 2.6, these applications are no longer provided.

  • Sergey Kiselev created several hardware platforms for RomWBW including the very popular Zeta.

  • David Giles created support for the Z180 CSIO which is now included SD Card driver.

  • Phil Summers contributed the Forth and BASIC adaptations in ROM, the AY-3-8910 sound driver, DMA support, and a long list of general code and documentation enhancements.

  • Ed Brindley contributed some of the code that supports the RCBus platform.

  • Spencer Owen created the RC2014 series of hobbyist kit computers which has exponentially increased RomWBW usage. Some of his kits include RomWBW.

  • Stephen Cousins has likewise created a series of hobbyist kit computers at Small Computer Central and is distributing RomWBW with many of them.

  • Alan Cox has contributed some driver code and has provided a great deal of advice.

  • The CP/NET client files were developed by Douglas Miller.

  • Phillip Stevens contributed support for FreeRTOS.

  • Curt Mayer contributed the original Linux / MacOS build process.

  • UNA BIOS and FDISK80 are the products of John Coffman.

  • FLASH4 is a product of Will Sowerbutts.

  • CLRDIR is a product of Max Scane.

  • Tasty Basic is a product of Dimitri Theulings.

  • Dean Netherton contributed the sound driver interface and the SN76489 sound driver.

  • The RomWBW Disk Catalog document was produced by Mykl Orders.

Contributions of all kinds to RomWBW are very welcome.


RomWBW is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

RomWBW is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with RomWBW. If not, see

Portions of RomWBW were created by, contributed by, or derived from the work of others. It is believed that these works are being used in accordance with the intentions and/or licensing of their creators.

If anyone feels their work is being used outside of its intended licensing, please notify:

Wayne Warthen

RomWBW is an aggregate work. It is composed of many individual, standalone programs that are distributed as a whole to function as a cohesive system. Each program may have its own licensing which may be different from other programs within the aggregate.

In some cases, a single program (e.g., CP/M Operating System) is composed of multiple components with different licenses. It is believed that in all such cases the licenses are compatible with GPL version 3.

RomWBW encourages code contributions from others. Contributors may assert their own copyright in their contributions by annotating the contributed source code appropriately. Contributors are further encouraged to submit their contributions via the RomWBW source code control system to ensure their contributions are clearly documented.

All contributions to RomWBW are subject to this license.

Getting Assistance

The best way to get assistance with RomWBW or any aspect of the RetroBrew Computers projects is via one of the community forums:

Submission of issues and bugs are welcome at the RomWBW GitHub Repository.

Also feel free to email Wayne Warthen at