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Comart Communicator

TimPowell said:
Thanks for all the dip settings, I will give them a try.

Funny that one of your CPU cards is only 9 away from mine in its serial number. Mines 1563. Are the IC’s socketed?. The later FDC controller i have, the chps a soldered directly into the PCB.

Interesting about the IBM drives, Would a hard sector floppy work in them? Not sure of the actual differences in the drives between soft and hard sector.
Do you know what drive’s were fitted originally? There’s a good chance I might have some.

The hard sector floppies were always going to be a high hurdle to get over. Reading some of the posts from the North Star forums, there are a few solutions that I could explore. But I’m putting this off until I know the rest of the system is working.

As to what i’m going to do next.
I have come to the conclusion that I need to be able to easily plug in a logic analyser to the backplane. I therefore going to make a PCB up to facilitate that.
I need to go do a better job on the disassembly of the eproms on the FDCs and get us much info from that as possible. For example port addresses, and how it inserts boot code into the rest of the system.
I also need a better understanding of the dip switches, especially on the memory cards.

That should keep me going for a few months.
If you come across any more info i would really appreciate it. Likewise i will do the same.


Regards Tim
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Hi Tim, the first few models were all socketed, we moved to soldered both for reliability, and because volumes went up and we switched to automated board filling and wave soldering equipment.

IBM drives I'm 99% sure would just sneer ate hard-sectored media - I don't think IBM ever went near hard sectored 5-1/4", though I think they did some early hard-sectored 8".

I may have a spare hard-sectored drive somewhere; I'll know in a week or two... The timing of all this is good. My wife has just confirmed that we have got a skip coming tomorrow to get rid of a load of junk in the garage that currently prevents me from being able to find a lot of the good stuff. I think in the early days we used Tandon then Teac.

If you try the later FDC, that is more likely support soft-sectored media on the IBM drives.

S100 extender cards used to be common. The card would often be a bit taller than a normal S100 card. The bottom had the normal S100 connector gold lands. The top would have an S100 edge socket.

Tracks ran from one to the other (often with some layout artefacts to avoid inductive coupling between tracks on opposite sides running parallel too long - though I get the impression this is an area you know a lot more about than me.,

Extending that design to include pins near the top on the board for connecting a logic analyser might be useful.

This weekend, I'll try starting to contact some old friends who may have more material than I. By the time I left Comart/Kode I'd been moved from technical to being the marketing manager, so when things kind of imploded, I didn't think to get any manuals - just did a deal with the CEO on a couple of boxes of kit from the rubbish bin.

Not to be nosy, but whereabouts are you? I'm Swindon based (Comart merged with KI and so moved from St Neots to Swindon).

As well as the kit I've mentioned, I have some FDDs, two of the old HDDs (I think) and what was at last sight a working 8086 C-DOS 86 system. Though I'm terrified to apply power to the old caps - I could be interested in trading some assistance in that area for some spare cards/drives etc., if that's of interest to you.

In the meantime if you think any of those cards would be a useful loan, just let me know and we'll work out a way of getting them to you.

Best regards

Dave.
 
Hi Dave

I’m happy to help you with your power supply, regardless of any trade.
Can you remember if its linear or a switch mode? Not that it makes much difference, just not sure where my isolating transformer is if we have to fault a switch mode. Normally you can just get away with changing any Rifa x2 capacitors.

I pretty sure I know were the problem is on my system, I just need to spend a bit more time isolating it.
I have only recently started having PCBs made just for testing. Something I would never have done in the past. It would have just been too much work, expensive and take too long. Now If anything, its too easy.

I’m in Woodbury near Exeter. But pretty much tied to the Exeter area due to my Partners’ ill health.

Regards Tim
 
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Hi Tim,

It’s definitely still linear – we didn’t go switch mode until VERY late in the day.

I may be wrong, but I think the only difference between my PSU and yours is that I may have the later big toroidal transformer rather than the older conventional one.

Exeter is no big trip for me, but work pressures are likely to prevent it this side of Easter.

I may get chance to check on the exact state of my "complete" system in the next day or so, though as I say I'm almost certain it's currently an 8086 or 286 system, so the cards and switches won't match.

Hopefully I can get a few minutes free over the weekend to try contacting a couple of old colleagues.

Best regards

Dave.
 
There‘s a Comart on ebay at the moment. Nice of them to show all their Dip switch settings.
 
Neat. I've also found some S100 XCOMP boards that we used in the very earliest Communicators for ST506 hard drives before we brought out our own HDC card for the CP-500.

Zippysticks, I'd count it a favour if you'd post the Dip settings anything else of interest when you get it.

Life here has been hectic, so I haven't yet hunted out old friends. Mind they were all several years older than I and it;s been a few years. Time may be against us in some cases. We'll see.
 
ExComart said:
Neat. I've also found some S100 XCOMP boards that we used in the very earliest Communicators for ST506 hard drives before we brought out our own HDC card for the CP-500.

Zippysticks, I'd count it a favour if you'd post the Dip settings anything else of interest when you get it.

Life here has been hectic, so I haven't yet hunted out old friends. Mind they were all several years older than I and it;s been a few years. Time may be against us in some cases. We'll see.
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Of course, I'll be happy to post details of the machine when I get it. I have a few other S-100 based machines that I can use as testbeds when I have had time to see what shape the Comart is in.
 
Actually, the jumper settings on all three boards in my system are all still visible in the Ebay listing here

I appear to have the same main set of boards, CPU, 64K RAM and FDC board as Tim.
 
Well, my machine arrived. Unfortunately, the case was smashed to pieces in transit (rather like @TimPowell) so I'll need to spend some time reconstructing it.
Tim - you did a good job on the case - what glue did you use for this brittle hardened foam ? Also - did you repaint the case as it looks great ?

As far as I can tell the machine does actually work but I could use a boot disk to test it @ExComart - if you manage to find one.
 
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I would like to say I did a lot of research into what to use to put my case back together, but I didn’t.

I just searched Amazon for plastic glue products and picked the ones with the highest review. Seems to have turned out ok but time will tell.

I used ‘JB Weld PlasticWeld Quick Setting Plastic Epoxy’ to stick all the bits back together. I then sanded back and used a plastic bumper and trim filler to fill in missing small bits. Missing large bits, I used a plastic putty to replace. JB WELD 8237UK JB8237 Plastic Weld Reinforced Epoxy Putty

I then sanded down and primed with JENOLITE Plastic Primer Aerosol a few times sanding down with a fine wet&dry between coats. Final coats were with JENOLITE Directorust Ivory White Satin.

I’m happy with the results and it seems strong.

I have nearly reversed engineered most of the Memory card, and i’ve worked out the dip settings. I’ll post when finished. The problem with mine is definitively hi resistance between chips and ic holders. Some of the ic legs are also very corroded. If anyone has got any ideas in what to use to clean them with i would appreciate.

Haven’t got any were near to the stage of booting up mine yet.
I pretty sure that the two discs that came with mine won’t work. One has mould on it. I was going to look at the NorthStar software and see if that was compatible.
When you boot you system without a boot disc, Does it come up with anything

Regards Tim
 
I should’ve mentioned that i didn’t remove all the old paint, i just smoothed with wet&dry and sprayed over the top. I had no reaction issues.
 
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Thanks @TimPowell - the case looks great. I think mine might have been in a slightly worse case with lots of small missing fragments of case and one corner completely missing at the rear. I chose to use a fibreglass resin mixture to reconstruct that corner and a Dremel to grind into a reasonable shape. I'll try an etch primer before painting.

I have not connected the machine to a terminal yet - my test has been limited to a power on and seeing it attempt to boot from disk before I took it apart to fix the case.

I'll let you know how I get on. I happen to have a couple of Northstar Horizons and associated disks so I'll try a few of those.
 
Sorry its been a while. Attached is the schematic for the Comarts Ram card. It's a bit messy and there might be a few errors, this always happens to me on a first draft of anything I reverse engineer. I've also left out decoupling capacitors. I have made up my own IC numbering refer to ic layout.pdf.
Also attached is the data on the prom. On the pdf version of the prom I have left out selections that would not be used. For example.. selections that would cause a conflict in memory bank selection or selections that totally disable the card. I'm Currently playing with linking a memory card to an Arduino but I will soon be going on to explore the FDC.
Other news. one of the bridge rectifiers suddenly decided not to work and I have have had few tantalum capacitors randomly pop. I am not a fan of changing every capacitor in a system but I think I'm going change all the tantalums as it makes me jump every time.

Any questions or spot any errors please let me know.

Regards Tim
 

Attachments

l wrote software on/for Comart Communicator using Concurrent CP/M using later models with 8086/80186. I have manuals for Conncurrent CP/M and Microfocus cobol. I have various formats of floppy disk with my sources and compiled code but cannot find any old software disks. I lived in Bedfordshire at the time and visited Comart several times and we sold systems based on the Communicator. I currently have no way of reading the disks.
Regards Dave P
 
Apologies for the lack of posts, sometimes life throws you a curveball. The Comart has been sitting under a dust cloth for quite a while, and only in the last few weeks have I managed to get back to it.

I’ve made some progress, but it’s still far from fully operational. Early on, I discovered issues with high resistance between the ICs and their sockets. I ended up removing all the ICs and cleaning the circuit boards in an ultrasonic bath. Some of the chips were so corroded that their legs had detached, so I replaced those ICs, along with a few others that tested faulty. I also replaced the regulators and some capacitors.

After reassembling everything, I ran a few power tests and attempted to boot it up. Unfortunately, nothing happened at that point. I connected a logic analyser and could see that some code was actually running. Upon inspection, it was getting stuck in a loop waiting for certain results from Ports 3. I suspected it was related to one of the UARTs, which I confirmed by monitoring their chip select pins. The UARTs are both D8251s—chips I wasn’t familiar with. Online reading suggested they can be a pain. There are two UARTs on the CPU card (see photo), and while both are initialised, it only expects a response from the bottom one, which I assumed was for the terminal. However, nothing was being transmitted.

IMG_3939.jpeg
Terminal
Port 2 Data inout
Port 3 Mode and status

Modem
Port 4 Data inout
Port 5 Mode and status

I decided that the best way forward was to run my own code.
Initially, I thought the code running on the CPU card was from the EPROM on the floppy disk interface card, but after tracing the circuits, I realised it was running code from a PROM, also on the FDC, which I had overlooked. The EPROM is used by a Z80 system on the same card. This handles all the floppy disk input/output and passes data to the main system via a port. I eventually made an adapter to plug in a ROM emulator instead of the PROM, allowing me to quickly write my own code to test the UARTs.
IMG_3935.jpeg

After some circuit tracing and adjusting bits in the mode register, I managed to get the traditional “Hello World” output from both ports. I had to replace a driver chip, the MC1488P, which had a short. Also, the modem’s UART CTS signal pin, which must be low for the UART to transmit, is routed to the CD pin on the RS232 modem plug. This confused me for quite a while but makes sense when considering its a modem port.


After reloading the original firmware from the PROM onto the emulator, I rebooted and got no response. A few hours later, after examining a disassembly of the original firmware, I realised it was waiting for me to press the ‘Return’ key. Once pressed, the terminal responded with:

BOOT.jpeg
‘Enter Boot Disk (0=HD200, 1=Floppy 1, 2=Floppy 2, CR=MW)?’

One other issue I noticed: instead of jumping to 0xF800, as set by the hardware DIP switches, it was jumping to 0xF000. This was working originally before I cleaned the boards, so I may have introduced this issue. At first, I thought it could be the DIP switches themselves, but on the logic analyser, I could see F8h appearing on the data bus from the switches (photo attached). It’s not a problem at this stage, as the PROM is shadowed at 0xF000, but I’d still like to resolve it.


LABoot.jpeg

Any ideas would be appreciated.

And that’s basically where I am.

You may wonder what happens when you press 0, 1, 2, or CR. The answer is, nothing—it locks up. The FDC’s Z80 may be expecting a floppy disk drive to be attached at this point, but I haven’t gotten that far yet. I don’t know what ‘MW’ means on the menu.
 
Comart Communicator! There's a blast from the past. In the 80s we used to sell Cromemco and Comart (and later Jarogate) so got to know them pretty well. I preferred Cromemco but they were a tad unreliable. Out of curiosity I had a rummage in my S100 box and found a number of Comart boards (see pic). I also have several CRAM-64s which I use in my Cromemco. The Comart boards were very reliable whereas the Cromemco 64KZ was always giving us problems. We used to swap out the Cromemco RAM boards for Comart wherever we could - especially where we were doing the maintenance. I have a few 10 sector floppies but I am not sure whether any of them are boot disks. I do not have a configurator disk. I am a bit busy at the moment otherwise I would try to plug up a Z80 or 8086 system and see if I can boot it. Also have a CRAM-64 manual but I think that there are pdfs on the web for this. I have thrown out the manuals for the other boards, unfortunately.
 

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  • Comart boards2.JPG
    Comart boards2.JPG
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zippysticks said:
Well, my machine arrived. Unfortunately, the case was smashed to pieces in transit (rather like @TimPowell) so I'll need to spend some time reconstructing it.
Tim - you did a good job on the case - what glue did you use for this brittle hardened foam ? Also - did you repaint the case as it looks great ?

As far as I can tell the machine does actually work but I could use a boot disk to test it @ExComart - if you manage to find one.
Click to expand...
The Comart Communicator was used in all the Byte Shops because Comart was the parent company. I think I remember that my pc booted from a MS-DOS disk and had 2 floppy drives; one for the program and one for the data.
 
ExComart said:
As it says, it's a Comart Communicator - and judging from the case and drives it will be an early CP200 model, so about 1978.

Built at Comart in St Neots, Cambridgeshire. Comart of course are now long gone. I had many good years there, including several as head of support.

Z80 at 4MHz,
Could be anything up to 64KB of RAM, but at that age, unless updated later, more likely 16K or 32K.
There are 2 x RS-232 serial ports on DB25 connectors running from the CPU card, one for the user terminal, one for serial printers.
There should also be a Centronics parallel printer port, also DB-25.
It's essentially a passive backplane with everything on S-100 cards.

The terminal needs to feed an RS232 TERMINAL (not monitor) which would also have provided the keyboard.

Any Wyse WY50 / WY30 / WY100 or similar era RS232 terminal should work.

It would have been running CP/M - and any version created for a North Star Horizon should work - at that time they used similar disk controllers and the same UARTS. Main difference was just which serial port was the printer and which was the terminal.

For a CP200 that old, there's a very high probability that you will require HARD SECTORED floppy disks. These will probably have been 107/2D media (or maybe double-density 207/2D), not the 104/2D or 204/2D media used on early IBM PCs etc. And they are fairly hard to source these days - that's likely to be your biggest problem. There are, I believe a few museums that have early NorthStars working, so it is possible that you might be able to get disks, and maybe an operating system, from one.

The keyswitch on the front is 3 position - OFF / ON with the RESET button enabled / ON with RESET disabled. The keys were only to prevent casual fingers pressing glowing buttons, rather than security, so they weren't unique, and were all variant TOK3. I can probably find a spare key somewhere, if you need one.

Even without media, if you connect a serial terminal (or get a suitable DB25/DB9 null modem cable, connect it to a DB/9 Serial port on a PC and run a suitable old dumb terminal program, you should see at least the power-on self test if its working. Baud rate would be 9,600, 19,200 or 28,400. 8 bit, no parity, probably one stop bit.

I don't think I've got anything to hand that would still run on it, but next time I clear out the garage I'll take a look.

Whatever you do, before you even think of turning it on, do please read up on the issues of old power supplies containing VERY BIG ELECTROLYTIC CAPACITORS, and take suitable precautions!

Big old capacitors that age left unused for that long have been known to explode if power is applied.

The reason that NorthStar stuff should work is that in those early days, Comart started manufacturing by making 3rd party replacements for NorthStar boards that were hard to source, then branched out into making their own systems.

But Comart's later systems were very much their own, and truly innovative.

The CP3000 and C-FRAME ranges were both based on a 386 with 256KB RAM/memory board, separate intelligent 186-based caching disk controller, and separate 186-based intelligent I/O controller - and communication was not over the S-100 bus.

The intention in the C-FRAME (a huge beast of a machine) was to have a network of these board sets, with a VERY large S-100 backplane being just the network connection between the sets. From memory, the design goal was something like 64 users running Concurrent DOS. Sadly, the merger with Kode killed the project before the clustered versions were complete. And the world was moving in other directions by then. But it would have been interesting to see what it could have been.
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There's a Comart Communicator at this museum according to AI - though it might be hallucinating. https://share.google/uog6iZwuWHApWhEoe
 
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