It is possible to revive old hardware using computer simulation. This project provides materials I gathered and generated a while ago when I was bringing an old Digitex 8200 computer back to life.

I could not find much documentation about this machine online. It is an all-in-one S-100-based computer comprised of the following components:

• Advanced Digital Super-Six SBC with:
  • Z80B CPU running at 6MHz.
  • WD2793 Floppy disk controller with Shugart 851 8” floppy drive.
  • 2x RS-232 UARTs via Z80-SIO.
  • Z80-CTC for counters/timers.
  • Z80-DMA controller.
  • 128K DRAM.
  • Boot ROM with monitor.
• Advanced Digital HDC-1001 Hard Disk Controller
  • Qume 2020 hard drive.
• AB Digital Design B810 RAM card (256K DRAM).
  • Supports banking, with common RAM from 0-3FFFh.
• California Computer Systems 2719 dual SIO / dual PIO card.
• California Computer Systems 2704 bus terminator card.

I bought this machine many years ago, but did not have a working 8-inch boot floppy disk for it.

Around 2008, I added support for this CPU card and some of the hardware to the SIMH simulator. Using SIMH, I was able to port a customized BIOS (CBIOS) for this machine and get CP/M 2.2 booting in simulation. With the simulator, I created a bootable disk image in ImageDisk (.IMD) format. This .IMD boot image was then transferred to a real 8" floppy disk. Using this disk, I was able to boot the computer.

In 2021, I decided to get the machine running again, this time using the 8-inch Qume 2020 hard drive. To my surprise, the machine booted up OASIS 5.6 Multiuser. I was able to use CP/M to back up the hard drive to 16 8-inch floppies, and then reassemble the pieces into a 16MB file that works using a DREM2 hard drive emulator, and also in SIMH.

Included in the distribution are:

1. My notes in CPM22/ADCS6_Notes.txt along with CBIOS source.
2. The Digitex Monitor ROM image and disassembly (somewhat commented) in Monitor/
3. The SIMH configuration file in sim/ for CP/M 2.2 and OASIS.
4. Some OASIS disk images in OASIS/

These instructions are for Linux and MacOS. The simulator can also be built for Windows using Visual Studio 2008 or later.

$ mkdir -p ~/src
$ cd ~/src
$ git clone https://github.com/open-simh/simh.git
$ cd simh
$ make altairz80

$ cd ~/src
$ git clone https://github.com/hharte/digitex.git
$ cd digitex/sim
$ ../../open-simh/BIN/altairz80 oasis_hd.ini

Altair 8800 (Z80) simulator V4.0-0 Current        git commit id: 69ab285e

DIGITEX Monitor version 1.2.A -- 10/06/83

Press "H" for Help

Attempting to boot...
Press any key to abort boot.

OASIS multi-user version 5.6 - 736K

Time (HH:MM:SS) 

Date (MM/DD/YY) 

06:25:06 Thursday, January 31, 1985

Logon please: SYSTEM

Logon at 06:25:09, on 01/31/85.

>

All about ImageDisk (.IMD) with tools: http://dunfield.classiccmp.org/img/

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