johnsonjh/cpm386

Source: https://github.com/johnsonjh/cpm386

CP/M-386

CP/M‑386 is CP/M for 386 protected mode, derived from CP/M‑68K.

• Overview
• Hardware support
• CP/M compatibility
• Build requirements
• Downloads
• Compilation
• Build output
• QEMU testing
• QEMU notes
• Included utilities
• Contributing
• Future plans
• Code statistics
• Mirrors
• License

Overview

CP/M‑386 is currently in the very early development stages.

• Full 32‑bit protected mode implementation with Ring‑3 TPA.
• Bootable via 3.5“ 1.44MB floppy disk MBR or GRUB Multiboot kernel.
• Supports VGA text (0xB8000) and/or COM1 serial (9600/N/8/1, 0x3F8) consoles.
• No floppy/hard disk/CD/USB/network/sound/other drivers (yet).

Hardware support

• Compatible with 386 (and later systems) with 2MB (or more) memory.
• Systems using either PC BIOS or UEFI (with CSM) are supported.
• VGA, 8042 PS/2, 8250/16450/16550 UART, CMOS RTC, and 8253/8254 PIT are supported.

CP/M compatibility

CP/M‑386 should be highly source‑compatible with other implementations:

The system currently reports BDOS 2.2 to applications.

• The CP/M‑386 BDOS is at full parity with CP/M‑68K 1.3 and CP/M 2.2.
• A large majority of the CP/M‑Plus (CP/M 3) BDOS is also supported.
• More than 60% of the DOS‑Plus additions have been implemented.
• Approximately half of the MP/M extensions have been completed.
  • The missing functionality is largely the multi‑user, multi‑tasking, message queuing, and process control calls that don’t apply to a single‑user CP/M implementation.
• Unique CP/M‑386‑specific BDOS extensions have been added to accommodate new features like direct video access, high‑resolution timing, PRNG, etc.

Build requirements

The following dependencies are required to compile CP/M‑386:

• AWK
• Cpmtools^†
• GNU Binutils
• GNU Coreutils
• GNU GCC or LLVM Clang
• GNU Make
• NASM
• QEMU (required only for testing)

^†Be sure to use cpmtools version 2.23 or later. Older versions may appear to work but have several known bugs.

Downloads

• Download the current CP/M‑386 build.
• View the GitLab CI/CD logs.

Compilation

Building CP/M‑386 is supported on current releases of NetBSD and FreeBSD^‡, and most recent Linux distributions.

The following are the minimum versions of Linux distributions that have been verified to build CP/M‑386 successfully: CentOS Stream 9, Fedora 36, Debian 12, Ubuntu 18.04 (with gcc-16 from ppa:ubuntu-toolchain-r/test), Ubuntu 22.04, Alpine 3.24, and OpenSUSE Leap 15.4.

• GCC build (recommended):

  make -Orecurse -j "$(nproc 2> /dev/null || printf '%s' 1)"
  make test
  

• Clang build:

  make -Orecurse -j "$(nproc 2> /dev/null || printf '%s' 1)" CC="clang"
  

• It is recommended to use GCC as Clang‑compiled i386 code is larger.
• Be sure to make clean if switching compilers or adjusting compiler flags.
• 32‑bit support libraries are required to run the test suite (make test).
• ^‡At the time of writing, FreeBSD is shipping non‑functional cpmtools2 packages with broken mkfs.cpm functionality. To successfully build on FreeBSD, you must rebuild cpmtools and ensure it is not linked with libdsk. If you receive a Disc rejected by driver error on FreeBSD from mkfs.cpm, your tools are broken and cannot be used to build CP/M‑386.

Build output

• The build produces two primary artifacts:

  File	Description
  cpm386.elf	Multiboot kernel image
  floppy.img	Bootable 3.5“ 1.44MB floppy disk image

You can download pre‑compiled binaries above.

QEMU testing

• Multiboot kernel (recommended):

  qemu-system-i386 -m 2M -serial stdio -monitor none -kernel "cpm386.elf"
  

• Floppy MBR loader:

  qemu-system-i386 -m 2M -serial stdio -monitor none -drive if=floppy,format=raw,file="floppy.img" -boot a
  

QEMU notes

• Use -nographic -display none -vga none to disable VGA video (and use only serial console).
• Use -serial none to disable the serial UART (and use only VGA console).

Included utilities

Contributing

• Do not open pull requests with large amounts of LLM‑generated code. These will be immediately rejected.
• There is currently no AI‑generated code in the operating system at this time (though there are some AI tests, comments, and analysis), as the project is intended to be as much of a learning experience for me as it is a useful OS port.
• Usage of AI (artificial intelligence) tools by contributors is currently permitted, subject to the same terms and conditions as the LLVM AI Tool Use Policy, but this permission may be withdrawn at any time and without notice.

Future plans

See FUTURE.md.

Code statistics

Mirrors

• The canonical home of this software is https://gitlab.com/johnsonjh/cpm386, with a mirror on GitHub.

License

• CP/M‑386 is distributed under the terms of the permissive MIT License.
• Bryan W. Sparks of DRDOS, Inc. dba DeviceLogics LLC, successor in interest to Digital Research, Inc.’s CP/M assets, explicitly grants an unlimited authorization to use, distribute, modify, enhance, and otherwise make available CP/M technology, including the CP/M operating systems and their derivatives.