CP/M-86 Hacking

Synopsis

A couple of experiments for fun with CP/M-86. The focus is on IBM XT CP/M-86 and derivatives on PC. But most of the tools work with the Just4Fun V20-MBC SBC.

Where to find CP/M-86?

The source for CP/M-86 doc, sources and binaries is http://www.cpm.z80.de.

A cleaned-up distribution and kernel is available at https://github.com/tsupplis/cpm86-kernel. This distribution is working well in virtual environments, patched with all known patches, 'y2k' friendly (it contains the version of tod which sources are in this project) and AT friendly.

Tools

File and Console Tools

Tool	Purpose	Usage and options
ls	Directory listing	ls [-h] | [-a] [-p] [-s|-r] [-l|-b] filepat filepat is [user/]filespec with wildcards. -a includes system files, -p pauses, -s/-r sort, and -l/-b select long/basic output.
rm	File deletion	rm [-h] | [-a][-i] filepat -a includes directory and system files, -i asks for confirmation, and -f deletes read-only files.
more	Paginated file display	more -h | [infile] infile is a [user/]filespec.
copycon	Copy console input to a file	copycon -h | [-a] filename filename is a [user/]filespec; -a appends. Ctrl-C or Ctrl-Z finishes input.
dump	Hexadecimal dump	dump -h | [-p][-r] [infile] -p pauses each page and -r selects raw output.
mode	Screen configuration	mode -h | option option ... Supports cls, cursor=on/off, statln=on/off, status=, fg=, and bg=. CP/M-86 1.1 for PC/XT only.
touch	Empty file creation	touch [-h] | filespec
wc	Count file contents	wc [-h] | [-a] filepat [filepat] ... Counts words, lines, and characters. -a includes directory and system files.
printenv	Display environment variables	printenv [-h] Status text supports \\s for space, \\ for backslash, \\u for upper case, and \\l for lower case.

System and Demo Tools

Tool	Purpose	Compatibility or build note
reboot	Cold or warm reboot	PC only.
cls	Clear the screen	cls targets VT52; clsansi targets VT100/ANSI terminals.
pause	Wait for a keystroke	CP/M-86 submit tool.
wait	Wait for n seconds	CP/M-86 submit tool.
tod	Replacement date/time utility	Removes the 78-99 year constraint and validates dates, including leap years. CP/M-86 1.1 for PC/XT only.
ver	Display BDOS version	dosver.com is the DOS counterpart for PC-MODE systems.
mem	Display available and system memory	dosmem.com and dosmem11.com are the DOS counterparts.
ball	CGA bouncing-ball demo	CP/M-86 assembly source in ball.a86; built with asm86, then gencmd 8080. Supported on CP/M-86 1.1 PC/XT, DOS Plus, and CCP/M-86 or Concurrent DOS with BDOS > 3.1. Based on https://www.z80cpu.eu/mirrors/klaw/bouncy.zip.
ballc	CGA bouncing-ball demo	C implementation of the same demo.
getch	Keyboard scanner	dosgetch.com is the DOS counterpart.
zpdump	Dump the zero page	pspdump.com is the DOS counterpart and supports -c to call DOS int 21h function 26h before dumping the new PSP.

Clock and Emulator Tools

Group	Tools	Purpose and compatibility
AT clock	attime, atinit	Synchronize the clock; atinit also displays a boot banner. PC/XT with an AT-compatible clock only.
RTC clock	rtctime, rtcinit	Synchronize the clock; rtcinit also displays a boot banner. Dallas clock at port 02C0h by default.
PCE emulator	pcetime, pceinit, pcever, pceexit, pcemnt	Clock setup, boot banner, emulator version, emulator exit, and host disk-image mounting. PCE only.

atinit, rtcinit and pceinit provide a quick configuration dump equivalent to what CP/M-86 1.1 displays on boot

CP/M-86 1.1, BDO 2.2
Hardware Configuration: 
 - System Memory: 640Kb
 - Available Memory: 607Kb
 - Math Coprocessor: No
 - Floppy Drive(s): 2
 - Hard Disk(s): 1
 - Parallel Port(s): 1
 - Serial Port(s): 2
Date now: 2021-9-27 22:17:39.0

All the C tools (rm, ls, mode, more, copycon, dump) benefit from the file specification pattern of Aztec C: [user]/[drive]:[filespec]. as well basic <file and >file redirects are supported.

What CP/M-86?

Unless mentioned otherwise, all the tools are working on

• CP/M-86 1.1
• DOS Plus 1.2
• Personal CP/M 2.04
• Concurrent DOS 3.2, DOS 4.1 6.21

For the following OSes, only the files tools work well. Interacting with the bios is generally prohibited (ATINIT/ATTIME and PCEINIT/PCETIME)...

• Concurrent CP/M 3.0
• Concurrent CP/M 3.1

Those OSes work incredibly well on PCE on floppy and HD images. This emulator is simple, small and works a treat. Fantastic...

PCE tools shortcuts

• pcetime has no option, It displays and sets up the clock using
  • BDOS Function 68h (T_SET) if BDOS >= 3.0 (Dates from 01/01/1978)
  • Using System Variable Control Block through BDOS Function 31h (S_SYSVAR) on BDOS= 2.2
• pcemnt needs to accomodate CCP uppercasing so an toggle character '^' is used to this effect:
  • /Mnt^/User/^JOhn/^test.img becomes /mnt/USERS/john/TEST.IMG

Build Environment

For this cross development environment, please use (https://github.com/tsupplis/cpm86-crossdev). It comes with wrappers for all the tools necesary.

Test Environment

• CP/M-86 1.1 for IBM PC XT patched at https://github.com/tsupplis/cpm86-kernel
  • CP/M-86 1.1, CCP/M-86 3.1 and PCP/M-2.0 can be found on (http://www.cpm.z80.de)
  • DOS Plus 1.2 and Patched kernel can be found on (https://www.seasip.info/Cpm/dosplus.html)
• The Excellent PCE emulator (http://www.hampa.ch/pce/pce-ibmpc.html)
• The most excellent CLI emulator for DOS and CP/M-86 is available at https://github.com/johnsonjh/emu2-cpm86 and delivered as part of the crossdev project.
• mtools 4 and cpmtools 2.20

Quick points on CP/M-86

Despite being a very primitive OS (in some cases actually enjoyably primitive...No time management at all outside of the clock, for example), it is possible to do quite an amount of things with a couple of good tools:

• DR CB86 2.0 (http://www.cpm.z80.de/binary.html)
• DR C86 1.11 (http://www.cpm.z80.de/binary.html)
• Aztec C 3.2 (Although Aztec C 3.4 or C 4.10 (ANSI) cross compilation from DOS is better) (https://www.aztecmuseum.ca/compilers.htm)
• Turbo Pascal 3.01A and Poly Pascal 3.1 (Turbo Pascal Sibling)
• RASM86 Macro Assembler (http://www.cpm.z80.de/binary.html)
• Microsoft Basic (http://www.retroarchive.org/cpm/lang/lang.htm) and Personal Basic Interpreters (http://www.cpm.z80.de/binary.html)
• PL/M-86 (Only cross compilation from DOS)

The big cool thing with this tiny OS is how small it is. I never configure more than 128K on my PCE VM and a single person can play as a hobbyist with it. As mention earlier it works also super well with the Just4Fun V20-MBC SBC (https://hackaday.io/project/170924-v20-mbc-a-v20-8088-8080-cpu-homebrew-computer). Cool other thing: it is Y2K compliant with TOD replacement above and a small visual hack. Yep no date management ...

It makes The early sources of MS-DOS as attractive. MS-DOS 2.X is far more flexible and has a bigger ecosystem than CP/M-86. This makes it more of a challenge ;-)

DR tools are available through (http://www.cpm.z80.de/binary.html) and many other sources. I found the last release of Turbo Pascal and Poly Pascal on a very exhaustive danish site focused on the RC700 series computers who are by the way also emulated by PCE. They are not PC compatible but both pascal are generic and work on the IBM PC based CP/M-86 family.

• (https://rc700.dk/software.php?name=RC750_TurboPascal_v3.01a)
• (https://rc700.dk/software.php?name=RC759_PolyPascal_v3.1)

But the files need to be extracted from disk images using cpmtools using the following definition:

diskdef rc75x
  seclen 1024
  tracks 154
  sectrk 8
  blocksize 2048
  maxdir 512
  boottrk 4
  os 3
end

Turbo Pascal 3.01A is the last releasse on CP/M-86 (Don't forget to configure it using tinst) and is in english. Poly pascal is also in english but the message file and the online help are in Danish. Not a big deal to translate them. Poly Pascal is really a twin, sibling or ancestor of Turbo Pascal. Kinda cool to play with it.

Macro assembler, C, Pascal, Structure Basic ... what else do we need?

Cross Compilation can be done either using DOS emulation (emu2, pce) or using a hybrid OS

• DOS Plus 1.2
• Concurrent DOS 6.21 XM

... run all the tools above (Both in their DOS and CP/M version) and you can test directly the cmd binaries.

A few CP/M-86 emulators for DOS exist (ame86.exe, cpm86.exe) unfortunately their sources are not to be seen anywhere and they woulld need a bit of maintenance. only rudimentary programs work.

Finally, Assembly using asm86 and gencmd can also be done but it needs to be done on CP/M environments (CP/M-80 or CPM-86 derivatives can be used)

It is a bit lacking on the tooling side though ... so I will port tools little by little for comfort sake.

• VE+ 2.03 (or better VE+ 2.33a) is really the only strong editor I found. (https://github.com/johnsonjh/vedit)
• A VI like editor is available for CP/M-86 at https://github.com/tsupplis/cpm86-vi
• There is no real solid CP/M-86 emulation as mentioned... But piggy backing the INT E0H API end point on emu2 perhaps? after all the 2 CP/M-86 and DOS 1.1 APIs are pretty much aligned...

Still it is a funny bit of discovery and archeology...

--

Companion projects

Project	Description
cpm86-kernel	CP/M-86 1.1 distribution rebuilt from patched and reconstituted sources
ccpm86-y2k	CCP/M-86 3.1 distribution rebuilt from patched and reconstituted sources
cpm86-crossdev	Unix CP/M-86 cross development project (compilers, emulation and tools)
cpm86-hacking	CP/M-86 miscellaneous tools and PCE emulator helpers
cpm86-cmdtools	CP/M-86 .cmd file manipulation tools
cpm86-ports	CP/M-86 application ports in C and assembler
cpm86-vi	STevie vi port for CP/M-86 and PC-DOS 1.1
pcdos11-hacking	PC-DOS 1.1 distribution, tools and notes