Roger Arrick .com

Intel Intellec MDS800 / MDS888
Development System 1977

11 Jan 2018

Roger Arrick MDS800 MDS888 Computer Click images for larger view

I worked on MDS systems in the 70s and purchased this one on ebay from a company in Ridgecrest California named Hill Electronics.

The system has an 8080 CPU, dual 8" DD floppy drives, PROM programmer, and a SCSI host controller with hard disk. I've brought it back to life and documented it here for others.

Personal Back Story

From 1977-1980 I worked with Intel MDS800 development system computers at Noakes Data Communications in Irving Texas. I was 16. We used them to design an 8080-based industrial computer which we manufactured for Shell Oil and some other companies. We had the 8080 In-circuit-emulators and the PROM programmer also. On my own time, I used the MDS800 to write a CP/M BIOS for our proprietary 8080 system which booted from 8" floppy drives.

In the mid-80s, the company went out of business and there was an auction which I attended. There sat 2 MDS800 systems with dual floppy drives, prom programmer and the ICE-80 modules. I bid against another guy and he eventually won. Later he came up to me and said "Hey, I just want the rack frames they're in, I'll sell you the computers". So I bought them, and we developed a good friendship. He was an airline pilot living in Hurst TX.

Life was hectic then with a family and small business and I never had the time to bring the systems back to life. Ultimately I sold or gave them away to a computer company in Louisiana. Later I was told they were put in a dumpster. :(

So, I'm very happy to get this machine and make it whole.

main: lxi sp, STKTOP ;Stack pointer. ;Sign-on message. call type DB CR,LF,'OD Cellular Automation',STOP ;Get blob char from user. mvi a,'*' sta BLOB


This ad from 1977 explains that an MDS888 is an enhanced version of the MDS800 with 64k RAM, more disk storage, CRT console, PLM and development support for 8085, 8048 and other processors.

Briefly: My MDS888 computer has dual-density floppy controller boards, 64k RAM, and a host controller for an external 20mb hard disk, dual 8" floppy drive box, UPP-101 PROM programmer, ICE80, ICE49.


Hard Disk Subsystem

After seeing the internal Host controller and browsing the seller's other auctions, I concluded that the external hard drive system from Radio Switch probably went with this machine and bought it. Took my chances and it paid off. It does indeed go with the system and boots. See the Operation section for details.


After the repairs, the system boots into MDS Monitor V2.0 !!!! It's very exciting to get this far. So much has to work at this point. I'd almost be happy with just this, but there is so much more that can be done.

Sometimes the floppy diskette will boot into OSIRIS V 3.00. A DIR looks like this. What is OSIRIS?? My guess is a customized version of ISIS or something for use with the external hard disk.

The 20m external hard disk boots into OSIRIS V3.00, does some reassigning of the drives then does a WDIR.
This reassignment sets the drives this way:
:F0: is HD partition #1 named SYSTEM.DSK See Directory page 1   Directory page 2
:F1: to HD partition #2 named APR86.LIB See Directory
:F4: is Floppy Drive 0 with floppy named OSIMAN.300 See Directory
:F5: is Floppy Drive 1 (mine doesn't work)

Sometimes it won't boot and just gives an Error 24 with a Status 11 or Status 13. The ISIS book tells me this is a disk error. The book doesn't make clear what the status # means. I fear this means the Hard Disk is going bad. There is no ripple on the HD +5, +12 power supply. Once it gave me a "bad executive checksum" so I suppose that's either the HD or possibly memory.


See the OSIRIS Operating System Archive page.

Investigations by Jack M. suggests OSIRIS might be a short-lived version of ISIS designed for the last version of the MDS888 before the MDS225 development systems were introduced. Jack asked to see the contents of the ISIS.DES file, here it is copied to screen, it's binary, so many unprintable characters but there is some ASCII clues in there. My first attempt at using the putty terminal emulator to capture the file as a session failed but I'll work on that.

Jack offers this potentially relevant history:
The Egyptian Myth of Creation. From Geb, the sky god, and Nut, the earth goddess came four children: Osiris, Isis, Set and Nepthys. Osiris was the oldest and so became king of Egypt, and he married his sister Isis.

Jack suggests this is an important part of Intel history and I agree. My goal is to archive all of these files once I get the hardware going correctly. 'First do no harm' is my motto. Currently I'm not able to format and write a new floppy disk and definitely don't want to write on the HD. I've ordered an ST225 HD also for future backup but most of the HD can fit on a stack of floppies if I can get that going.

ISIS-II Drive Organization

This chart is very important for understanding how disk drives are allocated in an MDS800 or MDS-II system. It depends on which controllers are in the system. The initial decision for which drive to boot from is made by the boot EPROM on the CPU board. Click for a larger view.

Intel PIII515 and other stuff

This batch of gear came with other things including an an ICE 5100 Emulator and a PIII515 80186 emulator. Here are some images:


And an Intel PGPIO board PWA 1000929-01A - Picture

Archiving Project

Very first project is to save the data on this floppy disk and hard disk. I know some of the hard disk is bad. There is likely a simpler way but first I tried the brute force method and used RealTerm with 8N1 parameters at 2400 baud to copy the DIR program to the console and capture it. The command is:


The captured file had an extra CR/LF at the beginning and 25 bytes of "COPIED :F0:DIR TO :CO:" CR LF "-" on the end which I deleted using this Hex Editor. Here is the binary of the DIR file (5747 bytes). Don't let the .txt extension confuse. So, it's a humble start. We'll see if anyone can load and run it.

Item's I'm Looking to Buy

Related Pages

Related Links

Copyright © Roger Arrick