New Datapoint 2200 owner.

[jdreesen]

It is indeed a strange setup. Note that the 4.8KHz clock is also responsible for the ROM precharge signal, which to my mind means that it must be synchroneous with the reboot_clock.......
Note that the actual contents of the bootrom is for a 2nd generation 2200, with the programmable display. I do not know compatible that is with the fixed font roms in your machine.

 

[MattisLind]

Yes. I know about the font-loading process. Mostly it seems to load exactly the normal set of character in the boot-ROM. However, my intention is to put some other code in there. For example the small test programs that are on bitsavers. Or I could just write something that inserts a pattern into memory ao that I can verify that it actually stored something in memory using a logic analyzer.

ROM precharge? Is that the Ar signal? Do you have data sheet for the Electronic Arrays EA49xx. I cannot find anything on it.

I have studied the schematic a bit more. I am a bit puzzled by the fact that the MR pin for two of the four address generating counters is not the TAPE MOTION signal. I find it weird that it resets the lower eight bits independent of the high 8 bits.

On the other hand ~TAPE MOTION is connected to ~Pl of the 74193 which loads in all zeors to the counters. Essentially the same as clearing the counter. So then there are two ways of clearing the upper half of the address counter.

I also tracked the TAPE MOTION signal a bit more and it is generated on board A2 by a mono stable one shot, with triggers not only the two strobes but also an or-condition of pretty much all signals that causes movement. Since the REBOOT signal will trigger both the rewind and forward signals one can be pretty sure that TAPE MOTION is triggered. Perhaps this is some kind of guard timer? It seems to be using quite big values of C and R.

Why are the two signals oe1 and oe2 of the ROM connected together but doesn't have a source. I guess the EA94xx is a MOS ROM. I am not sure if they have built in pull ups, but unless the inputs are TTL compatible I would expect some kind of source for those pins.

 

[jdreesen]

ROM precharge? Is that the Ar signal? Do you have data sheet for the Electronic Arrays EA49xx. I cannot find anything on it.

Actually, this site, which might be familiar to you, has the info http://www.datormuseum.se/peripherals/terminals/hp-264x.html


And oe1 & 2 have a simple pullup to Vcc, missed that in the schematic.

 

[MattisLind]

Actually, this site, which might be familiar to you, has the info http://www.datormuseum.se/peripherals/terminals/hp-264x.html


And oe1 & 2 have a simple pullup to Vcc, missed that in the schematic.

Aha. Wow. I had completely forgotten about that. I searched for EA49xx, EA4902, EA4904 but not EA4900. Maybe that would have been a hit on my page.

Still the /AR signal is puzzling me. How can the latch be clocked with a 300 Hz signal and still be able to read out data at a much higher rate? Is there something about the /AR signal I don’t understand. The reboot clk is almost 5 MHz, derived by dividing the main crystal by two and gate it through som gates.

 

[MattisLind]

I was lucky to be able to visit DDHF in Denmark. They showed a running GEIR computer from 1961 playing music. But that was not all. I was able lo loan a set of 14 cassette tapes which came with their Datapoint 2200.



So I spent some time trying to recover one of them. It turned out to contain a Basic interpreter on side A and a CTOS tape with editor and assembler on side B. I was able to start them in the simulator and they seemed to run just fine.





Now I just need to figure out how to operate the assembler program properly. I cannot seem to find any manuals on line for it unfortunately.

 

[voidstar78]

Really neat to see pre-1974 equipment like this. And - great looking emulator! Is that using or related to MAME? I mention this because recently (just a few months ago) the IBM 5100 emulator was brought into the nightly build of MAME - which one typically associates MAME with arcade machines, but it does other classic systems as well. The MAME API has a lot of utility, you could even integrate an actual image of a DP2200 to interact with (and it has lots of debugging support).

I've still not seen a running DP2200 or 1100 . There are some later model variants (1974 or later) - but yes it seems PSUs in early-early 1970s weren't the most reliable.

I briefly touched on the DP2200 in the Domesticating the Computer VCF talk (about halfway thru). It was a great pioneering system, but I think one of the tragedies is that one of the founders/owners died in a car accident? Somewhat similar situation in mid 1980s with Eagle Systems, story goes its founder died in car accident the very same day the company went public. (well, then there was also the tragedy related to the IBM PC dev team; some say its why Lockheed never returned to commercial aircraft -- and it was just a few months before the Challenger accident)

 

[Blunze42111]

I was lucky to be able to visit DDHF in Denmark. They showed a running GEIR computer from 1961 playing music. But that was not all. I was able lo loan a set of 14 cassette tapes which came with their Datapoint 2200.

View attachment 1283141

So I spent some time trying to recover one of them. It turned out to contain a Basic interpreter on side A and a CTOS tape with editor and assembler on side B. I was able to start them in the simulator and they seemed to run just fine.

View attachment 1283142

View attachment 1283143

Now I just need to figure out how to operate the assembler program properly. I cannot seem to find any manuals on line for it unfortunately.

Hi there,

I have a SNAP/3 manual which is good for the 5500 and beyond. There is also the 8008 instruction booklet from 74. If needed, pls reach out unicast, we had mail exchange before.


BTW: Has anyone gotten Databus compiler and interpreter to work? I have failed to find a media which works...

 

[jdreesen]

I've still not seen a running DP2200 or 1100 . There are some later model variants (1974 or later) - but yes it seems PSUs in early-early 1970s weren't the most reliable.

My 1100 was running for a few hours before the PSU blew again. It is not so much unreliable, but it is an utterly unsave design that would never come close to passing today's safety regulations.
Additionally I am in 230V mains territory, so I am reluctant to work on it.
I am designing a RAM board for 2200/1100 ( parallel versions onl;y) that would hopefully allow for a bootprom and USB i/f, but the project is still in its infancy.

 

[Blunze42111]

At the time when I worked on DP's, the PSU was regularily failing and every hardware technician told you to stay clear when the hood of the 2200 was opened. The PSU was responsible for some very heavy injuries from the current.

 

[MattisLind]

Really neat to see pre-1974 equipment like this. And - great looking emulator!

Thanks!

Is that using or related to MAME? I mention this because recently (just a few months ago) the IBM 5100 emulator was brought into the nightly build of MAME - which one typically associates MAME with arcade machines, but it does other classic systems as well. The MAME API has a lot of utility, you could even integrate an actual image of a DP2200 to interact with (and it has lots of debugging support).

Yes. I have tried HP Integral emulation in MAME and it is really good. MAME is quite complex and has quite steep learning curve IMHO. I am not really sure how to emulate the DP2200. On the TTL-component level or on the architecture level. In this case I feel that perhaps SimH would be a better fit. On the other hand the interactive debugging window in my emulator has been quite useful to me when debugging the emulator. Such a debugging window is not a standard feature of SimH. For now the DP2200 emulator will be a standalone emulator. But anyone that feel like it is free to take whatever they like of it and integrate in whatever framewoek if possible.

I've still not seen a running DP2200 or 1100 . There are some later model variants (1974 or later) - but yes it seems PSUs in early-early 1970s weren't the most reliable.

I briefly touched on the DP2200 in the Domesticating the Computer VCF talk (about halfway thru). It was a great pioneering system, but I think one of the tragedies is that one of the founders/owners died in a car accident? Somewhat similar situation in mid 1980s with Eagle Systems, story goes its founder died in car accident the very same day the company went public. (well, then there was also the tragedy related to the IBM PC dev team; some say its why Lockheed never returned to commercial aircraft -- and it was just a few months before the Challenger accident)

It was indeed an interesting pioneering system, but there were a few others that were in the same business segment at this time. I can mention the Incoterm SPD series and the Cogar C4. Programmable desktop machines (terminals?) with integrated screen and some kind of mass storage. Incoterm was founded in 1969 and their first products hit the market before the Datapoint 2200. Take a look at those as well unless you haven’t already!

Will view your talk in full when back at home. Sitting in the car right now.

 

[MattisLind]

Hi there,

I have a SNAP/3 manual which is good for the 5500 and beyond. There is also the 8008 instruction booklet from 74. If needed, pls reach out unicast, we had mail exchange before.

I am not sure the assembler is the same as SNAP3/SNAP4 for 5500. Unless it is already scanned it would be great if it can be scanned!

BTW: Has anyone gotten Databus compiler and interpreter to work? I have failed to find a media which works...

Among the cassettes from DDHF I dumped there were both a Databus 2 compiler and a Databus 2 interpreter/runtime. It can be tricky to work with cassettes but I think it should be possible to compile and run databus code using those.

I have been thinking of testing the workflow of editing code using GEDIT and put it on a scratch tape and then compile it and run it but haven’t had any time.

 

[Maxwood]

Yes. It would be great to find a CTOS cassette and then be able to duplicate that one. Apparently someone called "maxwooood" has one:

https://imgur.com/a/CVeBGvT

Meanwhile I started to look at the PSU. The PSU is located in the back of the unit and is mounted to a big heat sink.

The left part is the deflection amplifier. A 2200 machine is not using conventional raster scan. Instead it does "diddlescan". It paints the entire character and then goes on to the next. The right part is the PSU.

One annoying thing from a safety perspective is that all the transistors to the left above is connected to mains..

Then when I started looking at the schemtic I found out that the PSU in the back is not self-contained. There signals going in and out of the 50 pin connector which controls the PSU.

A very unusual design, but then switch mode supplies weren't that common in the early seventies.

If I understand the design correctly Q8-Q11 s a buck converter with L1 and CR5 which is supposed to create a regulated 60VDC which then fed into a push-pull converter around Q13 and Q14 with transformer T1. It seems to be self-resonant.

Apparently the 14KC control signal is coming from the 50 pin connector then all output voltages as well as sense and reference levels go through this same 50 pin connector which seems to end up in a backplane in the terminal. How nice to have live levels inside the backplane! I wonder how many Datapoint service engineers that were killed by this design while working on them in the field...

Need to figure out a way of testing the PSU out without killing myself...

Better late than never to this thread.

This was my imgur post and is one of two Datapoint 2200's in my possession inherited from my grandfather. He was an engineering executive with TRW and they invested in CTC/Datapoint and he was sent to work directly with Vic Poor and Harry Pyle on the development of the system, architecture and business, as well as the implementation of LAN/ARCNet between the programmable terminals.

Stay tuned for more pictures.

 

[gottahack]

Really nostalgic to see the work here. I went to work for Datapoint the summer after my first year at UC Berkeley, I think in '78. (They had a development center in Berkeley that had developed a COBOL compiler.) Sorry I don't have any parts or docs to share, though.