GitHub - johnsonjh/cpm386: CP/M-386: CP/M for 386 protected mode, derived from CP/M-68K

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

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 boot sector or Multiboot kernel.
Supports VGA text (0xB8000) and/or COM1 serial (9600/N/8/1, 0x3F8) consoles.
No 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:

System	BDOS coverage
CP/M‑68K 1.3	100%
CP/M 2.2	100%
CP/M‑Plus	74%
DOS‑Plus	62%
MP/M 2.1	50%

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
LZ4
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 the current releases of NetBSD and FreeBSD^‡, as well as Red Hat Enterprise Linux 9 (or later), CentOS Stream 9 (or later), and Fedora 36 (or later).

GCC build (recommended):

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

Clang build:

make -Orecurse -j "$(nproc 2> /dev/null || printf '%s' 1)" CC="clang" OPTFLAGS="-O1"

It is recommended to use GCC as Clang‑compiled i386 code is larger.
- Clang‑compiled builds will need to use OPTFLAGS=-O1 (or -Os or -Oz) to avoid exceeding the 384 KiB allocated for the ramdisk, or the kernel size + Ring-0 stack exceeding conventional memory.
Be sure to make clean if switching compilers or adjusting compiler flags.
You may need to adjust the make -j argument depending on your operating system (e.g., gnproc, sysctl -n hw.ncpu, getconf NPROCESSORS_ONLN, psrinfo -p).
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.

Docker build

If you are unable to build CP/M‑386 natively on your Linux distribution, a Docker‑based Fedora build is available:

docker build --progress plain -t cpm386/cpm386-build:latest -f Dockerfile .
docker run --rm -v "$(pwd -P)":/src -w /src cpm386/cpm386-build:latest

Build output

The build produces four primary artifacts:

File	Description
`cpm386.elf`	Multiboot kernel image
`floppy.img`	Bootable 3.5" 1.44MB floppy disk image
`fd.img`	Blank CP/M 3.5" 1.44MB floppy disk image
`hd.img`	Blank CP/M 8MB hard disk image

The mboot.sh convenience script (tested on GNU/Linux systems with GRUB2) can be used to create bootable multiboot media (such as a USB drive or SD card) using the cpm386.elf file.
The floppy.img file can be written directly to a 1.44MB floppy disk.
- NOTE: This disk image does not contain a CP/M filesystem. It can be removed from the drive once system is up and running.
The blank images are useful because CP/M‑386 does not yet have a FORMAT utility.

QEMU testing

Multiboot kernel (recommended):

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

Floppy boot sector 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).

Use make disks to create empty disk images. To attach them to QEMU, use:

-drive if=floppy,format=raw,file="fd.img"
-drive if=ide,format=raw,file="hd.img",index=0

Included utilities

Program	Description
`ACLOCKDV.386`	aclock (VGA text console version)
`ACLOCKVT.386`	aclock (ANSI terminal version)
`ALVTST.386`	Get Allocation Vector test (`DRV_ALLOCVEC`, BDOS 27)
`CAPSLOCK.386`	Caps‑Lock key behavior utility (BDOS 235)
`CLEARTPA.386`	Clears (zeros) and optionally verifies the TPA
`CLS.386`	Clear screen (BDOS 221)
`DELAY.386`	Delay test (`P_DELAY`, BDOS 141)
`DEMO.SUB`	SUBMIT demonstration
`DUMPDIR.386`	Directory entry dump utility (`F_SFIRST`/`F_SNEXT`, BDOS 17/18)
`DUMPFCB.386`	File control block dump utility (`F_OPEN`, BDOS 15)
`ED.386`	ED (A WIP port of the DRI CP/M Context Editor, August 1982)
`ENV.DAT`	Environment data file
`ESCTILDE.386`	Escape and Tilde key behavior utility (BDOS 237)
`FPARSE.386`	Filename parsing test (`F_PARSE`, BDOS 152)
`GETSN.386`	Display serial number (`S_SERIAL`, BDOS 107)
`GFXTEST.386`	Graphics and framebuffer demo (BDOS 229/230/231/233)
`HD.386`	Hex dump utility
`HELLO.386`	Hello world - the first CP/M‑386 program! (`C_WRITESTR`, BDOS 9)
`ILLEGAL.386`	Ring‑3 protection and exception handler test
`IOTEST.386`	File I/O BDOS tests
`JULIA.386`	Draw a Julia set fractal (terminal version)
`LRBC.386`	Query and/or set Last Record Byte Count
`LS.386`	List files (with sizes)
`MANDEL.386`	Draw a Mandelbrot set fractal (terminal version)
`MEM.386`	Memory map utility (BDOS 227/228)
`MORE.386`	UNIX `more`‑style pager
`NUMLOCK.386`	Num‑Lock key behavior utility (BDOS 236)
`OD.386`	Octal dump utility
`PAUSE.386`	Wait for keypress (`C_RAWIO`, BDOS 6)
`PIP.386`	PIP (A port of Zilog CP/M-Z8000 PIP v1.0A, January 1984)
`PRINTENV.386`	Print environment and system data
`PRNG.386`	PRNG test and demo utility (BDOS 253/254)
`PROFILE.SUB`	SUBMIT script (automatically executed at boot)
`RC.386`	Return code test and query (`P_CODE`, BDOS 108)
`README.TXT`	Sample text file
`REBOOT.386`	Reboot utility (BDOS 220)
`RM.386`	UNIX `rm`‑like interactive file deletion utility (`F_DELETE`, BDOS 19)
`SEROFF.386`	Disable serial console (BDOS 223)
`SERON.386`	Enable serial console (BDOS 223)
`STAT.386`	STAT (A port of Zilog CP/M‑Z8000 STAT v1.0C January 1984)
`SYNC.386`	Synchronize disks (`DRV_FLUSH`, BDOS 48)
`TERMTEST.386`	Terminal and keyboard test utility
`TEST110.386`	String delimiter test (`C_DELIMIT`, BDOS 110)
`TEST211.386`	Numeric format test (`C_DECNUM`, BDOS 211)
`TEXTMODE.386`	Query and/or set the text mode and cursor state (BDOS 229/230/231/234)
`TICKS.386`	High‑resolution timer tests (BDOS 225/226)
`TOD.386`	Get (and set) Time of Day clock (`T_SET`/`T_GET`, BDOS 104/105)
`TOUCH.386`	Create an empty file (`F_MAKE`, BDOS 22)
`TRUNCATE.386`	File truncation utility (LRBC aware)
`TRUNCTST.386`	Truncation tests (`F_TRUNCATE`, BDOS 99)
`TSEC.386`	Get date and time (`T_SECONDS`, BDOS 155)
`VER.386`	Display OS version (`S_OSVER`, BDOS 163)
`VGAFONT.386`	Load a text console font or restore the ROM font (BDOS 232)
`VGAOFF.386`	Disable VGA text console (BDOS 222)
`VGAON.386`	Enable VGA text console (BDOS 222)
`VGATEXT.386`	VGA text direct access demo (BDOS 224)

Contributing

Do not open pull requests with large amounts of LLM‑generated code. These will be immediately rejected.
There is no AI‑generated code in the core operating system at this time (though there are some AI‑generated 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

Language	Files	Lines	Blank	Comment	Code	Complexity	Bytes	Uloc
C	74	46336	8739	7922	29675	6062	1280486	17599
C Header	24	3344	652	1472	1220	11	122859	1618
Assembly	8	1865	327	413	1125	1	46692	965
Makefile	2	1706	333	215	1158	352	56926	823
Markdown	2	529	58	0	471	0	21756	418
Shell	1	291	86	62	143	30	8298	114
Linker Script	2	207	39	0	168	0	5137	95
YAML	1	86	6	15	65	0	3679	69
Dockerfile	1	47	8	12	27	4	1310	34
Total	115	54411	10248	10111	34052	6460	1547143	21640

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.