Modifications for Lifeboat CPM 2.2 to run on the Altair 8800 using a virtual floppy drive accessed over serial from a modern PC and matching software for the PC side.
The Altair 8800 had a few options for long term mass storage; the 8" floppy was one of the most common. These are hard to find and maintain today. This software allows to keep disk images on a PC and access them over a serial connection, either rs232 or USB.
Original code by Don Barber is licensed under GPL version 3.
CPM code license is available at http://cpm.z80.de/license.html.
Other code is subject to the original authors copyrights and their respective licenses.
Drivewire for the Color Computer https://sites.google.com/site/drivewire4/
APE for the Altair http://ape.classiccmp.org/
FDC+ https://deramp.com/fdc_plus.html
APE and FDC+'s software is Windows only. APE requires two serial ports, and FDC+ requires the hardware card. I wanted something that would work on Linux, could carry everything over a single connection, and didn't require special hardware. And it was a fun little project.
The software is coded for using the 2SIO IO addresses right now. It is straightforward to modify it for other IO cards. For example, if one uncomments the USBDATA/USBSTAT defines, it will use the s100computers.com Serial IO board USB port.
Enter the firststage.rom code into the front panel of the Altair at address 0. The code is:
076 003 323 020 076 025 323 020 041 302 037 061 032 000 333 020
017 320 333 021 275 310 055 167 300 351 013 000
This sets the 2-SIO card to 9600 8-N-1. Adjust the bootloader/firststage.asm as desired for other settings. Note this is the same as the 8K BASIC 4.0 loader so you can choose to use that instead if you have it in ROM or have the deramp.com Altair 8800c front panel with its code injection capability.
Reset and execute from address 0.
Run ./serialdrive.py /dev/ttyUSB0 (replace with your appropriate serial device). In serialdrive hit ctrl-] and enter 'sendsbl' to send the sbl.tap file. CPM should now boot up:
CP/M2 on Altair
48K Vers 2.20
(c) 1981 Lifeboat Associates
Modified 2022 Don Barber for Disk-over-Serial
A>
Congrats!
You'll need a copy of Lifeboat CPM 2.2. Grab LIFEBOAT-CPM22-48K.DSK from https://deramp.com/downloads/altair/software/8_inch_floppy/CPM/CPM%202.2/Lifeboat%20CPM/. Thanks to deramp.com for making this archive available.
You'll also need a copy of my altair2cpmraw scripts to build the images. Grab it at https://github.com/barberd/altair2cpmraw. You'll need to add the appropriate altaircpmraw diskdefs to your system.
I used the zasm assembler to build the software. Conceptually you could use any 8080 assembler, but might have to make minor syntax changes. Zasm is available from https://k1.spdns.de/Develop/Projects/zasm/Distributions/.
Right now the firstboot.asm, loader2.asm, sbl.asm, boot.asm, bios.asm, and user.asm files are all coded for MITS 2-SIO card using IO address 16 and 17 (10h and 11h).
By uncomment the USBDATA equate in the files, code for the s100computers.com Serial IO card is used instead.
Move the LIFEBOAT-CPM22-48K.DSK into the cpm directory. Enter the directory and execute ./makeserialcpm.sh, adjusting paths as needed. If it all works, you'll end up with serialcpm.dsk. Move this into the serialdrive directory.
Next, go into the bootloader directory and run ./build.sh. This will produce two files of note: firststage.rom and sbl.tap. Move sbl.tap into the serialdrive directory. firststage.rom is the code you'll need to enter into the front panel of the Altair. Run od -b 'firststage.rom' to show it in octal form or 'hexdump -C firststage.rom' to show it in hexadecimal form.
The firststage.rom bootstrap code is the same as that used for 8K BASIC V4.0.
Next, go into the serialdrive directory and run ./serialdrive.py and see what modules you need to install, such as 'serial' and 'xmodem.' Install them either from your chosen distribution or by using pip. When all set, start it up with ./serialdrive.py /dev/ttyUSB0 adjusting the serial device as appropriate.
Hit ctrl-] to bring up a menu. Hit enter on a blank line to return to the session. Here are the descriptions of the menu options:
Exit the program
Start debugging. This shows everything sent or received. Its quite noisy but can be helpful if you're having serial issues. I found a few bad chips on my serial board this way.
List mounted disks
Use this to mount new disks. For example 'mount 1 zork.dsk' will mount zork on drive b.
Use this to unmount disks.
Use this to send the bootloader tape after you've entered the first stage.
Use this to send a raw file straight. Enter 'sendfile filename'
This will initiate an xmodem get. Enter 'xget filename'. This menu option is rarely used as the 'dsput' command inside CPM will trigger it automatically.
This will initiate an xmodem send. Enter 'xsend filename'. This menu option is rarely used as the 'dsget' command inside CPM will trigger it automatically.
This will send a ctrl-].
These software programs are loaded onto the CPM disk. They initiate xmodem send and recieve to exchange files with the host system. They send escape codes that will automatically trigger the appropriate xmodem calls inside serialdrive.py so you won't have to use the menu options of 'xsend' or 'xget.' Just run DSGET.COM or DSPUT.COM inside of CPM.
These are minor modifications of Mike Douglas's PCGET/PCPUT software; credit goes to him.
Use standard MOVCPM/SYSGEN processes to resize CPM. Refer to the Lifeboat CPM manual.
Um...probably. It might require a slight modification to serialdrive.py's use of select(). Everything else should work just fine.
The menu could use several improvements. For example, there is no error checking that disk files actually exist.