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Searching for IBM S/23 Datamaster users

RetroAND

RetroAND

Experienced Member
Joined
Feb 14, 2023
Messages
112
Location
Andorra
Greetings,

I acquired an IBM System 23 "Datamaster" a couple of weeks ago. I have found many people over the not so many places where this computer is being discussed where they stated its non-reparability (the motherboard was designed as FRU, after all).
As I am in process to repair mine, an exhaustive study of the boards is being made. At the end of this phase, I should have a preliminary technical documentation and for the sake of completeness I would like to ask members of this forums who currently have (or had in the past) specimens of this systems with issues with the boards if they would share their knowledge, as small it could be. That should help me prepare a list of malfunctions which would help me in getting some directions to achieve fixes for them.

Regards
 
I don't now much about these, but I did make someone system disks not too long ago from this repository. He reported that the all the disks worked great.
 
bolex said:
I don't now much about these, but I did make someone system disks not too long ago from this repository. He reported that the all the disks worked great.
Click to expand...
Yes, this computer is shrouded in secrecy... in reality that is what is keeping all those units down. It's for this reason I'm documenting them, I would like to repair mine and with what I may find help other users to get their computers up and running.
Thank you for the images. They may come very handy when the appropriate moment arrives. It's very curious, my first contact with any (ex) Datamaster user was @NF6X. Love to see he made those backups.

For in case any user with non-functional unit information reaches this post, I would be interested in:
  1. Model (5322/5324)
  2. Variant (number which describes the amount of ram and drives)
  3. Region
  4. Issue(s)
    1. Symptom
    2. Suspect(s)
    3. Attempts to solve
    4. If issue is solved
    5. Solution (if any)
  5. Other related activities, such as documentation and search
I have a related but somewhat off-topic question: being 8085 based, why is this computer considered as "minicomputer" and not "microcomputer". It is bulky for sure but I've seen other bulky microcomputers while I've been collecting... I just don't understand.

Regards
 
RetroAND said:
I have a related but somewhat off-topic question: being 8085 based, why is this computer considered as "minicomputer" and not "microcomputer". It is bulky for sure but I've seen other bulky microcomputers while I've been collecting... I just don't understand.
Click to expand...
The S23 uses System/34 BASIC. Something that runs minicomputer software could well be considered a minicomputer. The S23 could also have the same maximum 256K of RAM as the System/34. All of which would make it distinct from the usual 16K microcomputer of the time.
 
RetroAND said:
Yes, this computer is shrouded in secrecy...
Click to expand...

It was an evolutionary dead end, quickly replaced by the IBM PC at a time when IBM was producing dozens of incompatible small systems
and was the immediate ancestor to the PC, many of the same people worked on it in Boca.
Fun fact, the expansion bus of the PC was the same as the Datamaster, with the connector reversed to keep people from putting cheap PC cards into them.
You could create a whole separate category for IBM small system oddballs like the 5100 series, the Datamaster, 8100, Office System 6, and Displaywriter
 
Last edited:
Al Kossow said:
It was an evolutionary dead end, quickly replaced by the IBM PC at a time when IBM was producing dozens of incompatible small systems
and was the immediate ancestor to the PC, many of the same people worked on it in Boca.
Fun fact, the expansion bus of the PC was the same as the Datamaster, with the connector reversed to keep people from putting cheap PC cards into them.
You could create a whole separate category for IBM small system oddballs like the 5100 series, the Datamaster, 8100, Office System 6, and Displaywriter
Click to expand...

Yes, it is hard to not notice his very short lifespan compared to previous IBM products. But when commenting about the secrecy, I meant they did take the effort to mark every single integrated circuit in the board with their own internal reference in order to conceal how did it work. Nearly half my life collecting those things and I have never seen anything closer to that.🤔

Yes! I found in the technical reference manual the pinout and it does really seems the same with very few alterations. When I picked it up I didn't know how similar many things would be between the PC and the Datamaster. It is a very special piece of history. 😉

Wait a moment... Can I actually create categories in here? I thought only admins could do it...😵‍💫

Regards
 
Yes, I've got a System/23 along with a complete documentation, software and training library... See below:
1677177242082.jpeg1677177222167.jpeg

At some point in the near future, I'll get started on archiving the documentation, the many software disks and the training cassettes.

-Chris
 
cchhrriiss11 said:
Yes, I've got a System/23 along with a complete documentation, software and training library..
Click to expand...
Absolutely amazing. I know it stinks to ship anything, but I'd love to help archive disks/scan documents if you need any assistance.
 
Good morning,

I have a near-complete identification of all the integrated circuits - but five - which compose the system board. Months ago I also identified its DRAM ics. For the success in the memories I have to thank @modem7 for having saved the datasheet in his website, a member of VzEkC e. V. Forum nicknamed slabbi for his knowledge and guidance. Back then I still hadn't found the bitsaver list of components. Using the card pinout from the maintenance manual I was able to identify two 74LS244 (confirmated later using the foresaid list).

I have seen many sites around the net which claim IBM placed the memories in piggyback due to reliability concerns. This claim is both unfounded and incorrect.

When I examined the board I started assuming this claim as true, but then my model is 64 KB and as a result this would mean half of the RAM would be missing. Also, there was something strange in the number of pins of those memories... because my tests were indicating they were from the 4116 family but had more pins and more refresh signals.

Thanks to slabbi I could successfully identify the memories and the first place I could get the datasheet for them was at minuszerodegrees (so thank you @modem7).

The memories used by the IBM System/23 family of computers are the infamous Texas Instruments TMS4132. Basically, two variations of the 4116 with more pins but with the same dice, most of the new pins being NC and designed to be piggybacked together to provide 32Kx1 bit. So, it was not IBM who piggybacked them but TI, in the same way the TMS4108 was.

Repairing the memory board

This leaves three ways to repair the board:

Option 1: desolder every couple of RAM ICs from the board, separate them and test them. Then order a replacement. Note that the top and the bottom ICs are different. Unless another S/23 is cannibalized for parts the fix is visible.
Option 2: desolder and test the momory ICs as in #1 but replace them with 4116 soldering wires in the pins in order to adapt those on the already existing design.
Option 3: replace the board.

In my case, I went with option #3. As every single integrated circuit has the IBM P/N stamped and the actual TMS4132 are expensive the first option was discarded. Going with option #2 was also out of the scope, as lots of 4116 have already overreached their lifetime and are also failing. For this reason I am designing a memory replacement not based on old memories and leave this board as unaltered as possible - heck, even its capacitors smell from IBM... - it seems so distinct from other memories I have seen in 11 or 12 years that I am considering exposing it in a frame.

Then I had to stop... but I have resumed, even if briefly.

Last week we dumped some of the ROMs, but due to their fragility I have finally opted to change the method for a while. The 8085 is to be extracted and tested in another computer, a TA Alphatronic P2. At the same time, the processor in the S/23 is to be faked with a Pi3A. Some other signals in the board are also to be read by the pi. This way I should be able to discover I/O ports in a controlled way from my PC.

Al Kossow said:
It was an evolutionary dead end, quickly replaced by the IBM PC at a time when IBM was producing dozens of incompatible small systems
and was the immediate ancestor to the PC, many of the same people worked on it in Boca.
Fun fact, the expansion bus of the PC was the same as the Datamaster, with the connector reversed to keep people from putting cheap PC cards into them.
You could create a whole separate category for IBM small system oddballs like the 5100 series, the Datamaster, 8100, Office System 6, and Displaywriter
Click to expand...

@Al Kossow Question for you: imagine I had a prototyping card for PC. I guess I would have to rewire every single signal if I wanted to use it, isn't it? 😵‍💫

Thank you everybody
 
Hello,

My S/23 is up and running again.
I have to continue with the main romset, but I have successfully dumped its MCS-48 keyboard firmware. Actually it is running with a 8749h with the extracted firmware with no issues. Many of the keyboard issues were found to be result of loose contacts in the pin socket connectors of the wires. Solved this issue, the computer did not complained about it again.

I am open to help anybody with a S/23 in any way I can. My ROS is fine.

Seeing how the tests seem to work, I have little doubt that fully expanding its memory could be easily feasible.

By the way, if anybody has underline 10-1F in the initial diagnostics but the ROM is present, it means your sockets or the IC's pins are damaged. In the first case, just replace them; in the second, it would be better to solder the memory into a socket. If that does not work, find an adapter pin-compatible with MOS/CSG 2364 (Enable High) to use a standard EPROM/EEPROM/Flash/whathever.

Thank you
 
Errata:

Sorry, I found an error in the above post. The range to check is 0x09-0x19.

Addendum:

When testing RAM it seems to resolve the test in the same way the ROMs are. Therefore I have an hypothesys which I am unable to verify at this moment: this computer does not use jumpers to configure memory (others than in the card per se), but it is made by software test and should be recognized during initialization, resulting in a "missing" result in case it is not found (or improperly jumpered, also with loose contacts in the PCB-Edge connector).
 
RetroAND said:
... If that does not work, find an adapter pin-compatible with MOS/CSG 2364 (Enable High) to use a standard EPROM/EEPROM/Flash/whathever.
Click to expand...
Errata: It is Enable Low.

My immediate memory does not work as expected and whenever I recur to it I may remember with more errors than usual. I would like to apologize for that.

Addendum:
As of yesterday's evening, the romset was successfully backed up for preservation. As there is still an unidentified DIP-40 present of the board I would refrain from the word "complete" until I determine if it is a mask/otp programmable element. The dump includes the 16 ROMs targetted from the beginning, a 17th which I think is the character generator and the 4048 microcontroller program.

Regards
 
Yesterday the floppy controller was modded to enable the external floppies 3-4, however the idea of adding a gotek may be unfeasible as the controller directly drives the motor by controlling the polarity on the rotor. Therefore it will be difficult to transform access0-access1 to /step+/dir.
Today @retrolab was able to make it read a floppy and execute a program from there.
 
As of today I learned the order for most EPROMs when decoded. Therefore a simple replacement for all ROMs would be possible. I forgot to check two of them, 02 and 09. A 27c010 should be able to replace them all and, as stated, their order is known to me now. Part of the jumper wiring around the ROM area has also been found.

On the floppy side of today, while we haven't been able to load anything else than the "Learning" floppy, we have been successful in creating an empty volume by writing that image and erasing all files in the disc later on the Datamaster.

Next thing to document after the two ROMs are the enable signals which feed the selectors studied today. That would help to reveal each memory's logical page position in the global memory map.
 
By wednesday I profundized the study on the selectors in order to find the best place to hook a rom replacement prototype I am building. The system was down until today - I was too tired to finish the work on it. The way it failed in-between also gave information about how would the computer react with failing selectors or bad roms. Also gave me an insight of the system per se - the entrypoint is at ROS 02 (02 and 09 are not connected to the 74LS138, therefore they are the fixed ROS page, with 02 being the lower one).

With a disassembler and an EBCDIC table I was able to locate various strings inside the boot roms - most of them were from BASIC, but I was happy to read "COPR.IBM 1982". The program signalled to a series of ports - they are still unknown, therefore a port listing should be carried. I have a 27512 to 2364 adapter on which I placed an 8KB image - basically the following program:

Code: 
.org 0
xra a
dw 4094 dup (00d3h)

.org 1ffdh
jmp 1

In a few minutes I will test port 0, which I know it is used. Other ports should follow.
 
Hello,

We have tried every image available to us, but unfortunately only the "Learn" one is the only one we have been able to write successfully. I don't know if we miss something important or something happens with the image. Does anybody know?

Thank you very much
 
RetroAND said:
Hello,

We have tried every image available to us, but unfortunately only the "Learn" one is the only one we have been able to write successfully. I don't know if we miss something important or something happens with the image. Does anybody know?

Thank you very much
Click to expand...
If the disk read good on a real System 23 (Datamaster), I would run the utility to check the source diskette for disk errors.
If there is none, then your system and software doesn't like the original source diskette. Your hardware and software configuration
is misreading some the diskette contents. Your Message doesn't state the diskette type, 2D, 2E and if it is hard sectored or not.
..
So there is not much I can really point out to you in this text message.
You should also try another manufactures diskette Archiving program. if the other one works, this should indirectly answer your question.
With how the Datamaster is/was designed it is possible to copy protect disks, and key diskette some they only run on selected systems .
Feudal Systems/Mil uses only.
 
It is interesting that you could only get that disk to work. I did make some disks for someone a few months back and that was the only disk that they could get working as well. Maybe there are just a bunch of bad disk images out there.
 
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