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Comart Communicator

G

Glen M

Experienced Member
Joined
Apr 27, 2020
Messages
57
Location
Belfast, Northern Ireland
I noticed this old box for sale locally but can't find much online about it. Seems to be Z80 based, 64k ram and runs CPM?

Don't really know the first thing about CPM to be honest and at £50 I'm not sure if this is worth it. Comes with the computer and monitor only, no keyboard.

Does anyone know anything about this and if I did buy it does anyone know were I could find software to run on it?

1ykovm3.jpg
 
Case is nice and If the drives turn out to be OK then 50 pound is not too much is it ?
 
Without a keyboard you probably won't get very far, unless perhaps it communicates via a serial port. What kind of keyboard port does it have?

I'd suggest opening it up and taking some pictures of the insides. Perhaps they just repackaged the guts from some more common system?

I'd hate to part out a system like that, but I'd agree, those full height IBM branded drives would likely get snatched up on eBay pretty quickly.
 
What little I can find on it suggests it uses standard serial terminals so getting a keyboard and display working with it should be straight forward. But then, it is a S-100 system and who knows what cards are in it. Top of the line Comart boxes could be very impressive.

50 pounds? Well, if the cards are still in it, you could probably part it out to other S-100 users for more than that even in the worst case of such bad damage the system can't be fixed.
 
I'd say for 50 GBP I would rate that value for a working S100 power supply and case. I know the comart brand and remember it well.

Anything could be inside, I'm sort of interested!! Where is it advertised again did you say :)


marcus
 
If the I/O is serial, then what is the "monitor"? Is it actually a terminal? Please post some pictures of that too.
 
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.
 
The above computer ended up on my workbench in Devon Uk. Unfortunately, it didn’t have a good journey, turning up in a lot of bits.

1672067031048.jpeg
I have rebuilt case, and I have just finished the Power supply.


1672067074689.jpeg

When you find that all fuses blown you know that something is wrong. In this case all the
Tantalum capacitors on the disk drive power supply were a dead short. The mains input filter was leaking down to earth and the smoothing capacitor on the -18v was also leaking. I also changed the -5 volt regulator on the disk drive PSU, despite not being used, as it was outputting -19v.

1672067106511.jpeg

I’ve just started on the main computer itself.
I’m not getting anything on the serial outlet, but I can see, using a scope, that there is some activity on the address and data lines, so its doing something.
I was wondering if anyone had any schematics or know what the dip switches should be set to.

The Model is C100

it has 4 memory boards each at 64k MEM-04A Rev B

It has a Floppy disk controller FDC-0CA Rev B I also have a spare FDC but it’s a Rev D

And a CPU board CPU-00A Rev C

The FDC has its own Z80 CPU and an eprom, while the CPU board has a z80 but no eprom.

Am I correct in saying that the system boots off the FDC which then loads the memory for CPU board?
I’m also interested in any history about the company

I have never worked on S-100 systems before so it might be a bit of a learning curve.
 
Welcome to the forum @TimPowell !

This is a really good write up of the machine, and the work that you have done on it, so far. It’s unfortunately that it was damaged in shipping, but it seems to have found a good home.

I’ve had a number of systems with heavy internal components arrive to me broken, as a switch did just last week. It’s very annoying, and I’m glad that it wasn’t terminal, in this case.

- Alex
 
Hi Tim, can you please to and post some photos of the front and back of each of:
  • One of the memory cards,
  • The CPU
  • The FDC?
Something is a little odd either in the cards or my memory. The base Z80 system normally only supported 64KB total for CP/M, though it is entirely possible that it was running MP/M or C-CPM and using multiple cards to provide banked memory. If so, there would probably have been an additional multi-port serial board in there at some time. Can you confirm how many flat cable sockets are mounted on the back panel, or if there are scratch marks that suggest more?

It definitely booted from the main CPU. I can't actually remember a separate Z80 on the FDC, which is odd, though it's been a few years - we did do some work with intelligent cacheing controllers, but I only remember 80186s for those.

Also I see a card running front to back on the left hand side - that looks like an HDD formatter board - is that twin floppies, or one floppy and one hard disk? Can you photo that board, and confirm where the cables for it run to/from?

It may be that although it started life as a CP100, it got upgraded somewhere along the line, or it may be something like a CP520 that's been downgraded.

I've got no records of the switch settings, but I have contacts who still might.

Let me know if you don't have a key for it. In a couple of weeks I'm due to have a cleanout in the garage - I may have some spares still.

I may also have spares of one or two card types, though I think that most of my cards are for the later 8086 S100 systems that we built.

I'll also post some pics of the Comart I'm getting ready to restore and what bits I have.

The earlier rev FDC may be one that only drove hard-sectored disks and drives, the later one is more likely to support both hard-sectored and soft-sectored.
 
Hi

Looking at the CPU card, the middle bank of dip settings are all set to zero. I think these are set incorrectly. I am assuming that the P,O,J dip setting on the CPU card is like the Auto Jump setting on the Northstar system and needs to point to some executable code.
Looking at the address and data lines with a scope the FDC is running code from its Eprom
While the CPU card the address lines are just counting, it’s not finding any code to run.
A dump of the Eprom’s show that there is a menu on the Eprom’s for disk settings, but there are more options on the REV D eprom.
The card running front to back on the left hand side is just one of the two floppy drives
Thank you for the offer of a key, but I did find one.. Regards

A7ACBD8A-628E-4B48-BFB0-611997A66AE2.jpegCDD50E75-3C8D-4207-91FF-513A52074E5D.jpeg CPU card

B69D4A41-8EB3-4017-B4C4-BE3FAC2E98FA.jpeg4208FCEB-3A97-461B-8844-4F7C100127B4.jpeg FDC card
FB0C4F24-0301-4F34-944B-3AE97A64040A.jpeg653DC04F-C80E-4AB7-A18C-64B4D08CA429.jpeg Memory
 
OK, I'll try to put some feelers out later this week to see if I can find anyone with some manuals or a better memory than I have. I still have contact details for the former head of software/firmware development - he may know, or he may still have contact details with the lead hardware developer below the Tech Director.

I'd completely forgotten the internal Z80 on the FDC - just shows how memory goes.

Giving it all a good clean would be a good start - the gunk on some of those pins could be shorting things - on the CPU board, just to the left of the switches, the first IC in particular seems to have quite a bit of something on the lower two right pins.

The counting on the addresss lines of the main CPU is actually encouraging - there was a basic system diagnostic test in there that included a memory test, which could well be what you're seeing. Some very vague and distant memories stir - there may have been a switch setting somewhere that forced it into doing a factory "soak" test, in which the ram test only ended when told.

Alternatively a switch error somewhere could be causing it not to see the FDC and so restart. Or I may be remembering a later revision of the card... Or I may be thinking of one of the higher CPU cards - we did 8086, 286 and 386 main CPU cards and 256KB memory cards for them.

Do you have any form of serial terminal anywhere, or a PC that can run a simple terminal emulation on a serial port? That would be my next step; I can see there that one of the serial ports is switched to 9600 and the other to 1200 - those switches at least are safe enough to play with, and if it is the memory test, you should be able to see what's happening - you might even get some diagnostic information on why the memory test never ends.

You **may or may not** need to be using a 2-3, 3-2, 7-7, null modem cable to connect to a PC.

I'd also try with only one memory card in, trying each in turn.

Also can you post the make and model of any floppy drives or hard disks you have in there?

When I get a chance (which may be a few days) I'll get some photos for you on the switches on some of my cards. Which may or may not have been accidentally changed in the meantine as they aren't in the chassis, which was last left with I think an 8086 CPU card in, though I do still have a complete Z80 card set, I think.
 
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I would really appreciate any information you could find. As i’m have never worked on a S-100 bus system before and it’s a bit of a learning curve on how things Work.

I took the time to hook up a logic analyser to the Z80 on the cpu card and later on the FDC you can get a far better understanding of what’s happening than just using a scope.

6B3CD2E8-E962-4940-BB43-F67FBC2D95F7.jpeg4000A85F-C4D2-448D-B6E8-68BA30F5F80D.jpeg

I’ve confirmed that the P.O.J dip settings are a, one time hardware, jump address on a CPU reset. I have also found, which was confusing me, that the switch ON position is a logic 0. There are five switches marked 15,14,13,12,11. If all switches are in the ON position the jump address is 0000. If all switches are switched off the jump address is 0xF800.None of the jump address are finding any code to run, But the &F800 address, which it was originally set to, is finding something but it’s gibberish. It could be that one of the bus buffer chips is not working correctly. I will try different memory cards and see if this makes a difference.
I am slowly cleaning the chips as I work through the CPU card. There is no prom or eprom on the cpu card so it must get its code from somewhere else.

The CPU card did stop working at one stage which I traced to the z80 not getting a reset signal. This turned out to be a damaged Hex inverter chip. Tracing out the reset circuit I noticed that the reset from the front panel is on the backplanes Pin 76 while the standard s100 back-plain its on pin 75.

Looking at the FDC a bit closer. I’ve done a quick disassemble of the eprom and traced the program while it ran on the FDC Z80. It carries out its own on board memory check, which it passes, and then locks into a loop waiting for an input bit to be set.

I’m currently tracing out the CPU buffers to the buss. It’s slow but strangely relaxing.

Regards Tim
 
Sorry i forgot the drive information.
No hard drive but has two floppy drives both Tandon TM100-2A. They both seen better days.

8F515E33-693E-4CE5-9AA3-C0C181DD6B46.jpeg

There were two discs in the drives, but I would be very surprised if they still worked. Both discs are hard sectored.
4432DB13-EAED-4500-8949-4462533C04D7.jpegFBF51B7C-580D-4FBD-A272-9EA460F472D7.jpeg

Regards Tim
 
This is all ringing bells. Including a very loud one about the address bits being inverted and the F800 start.

I'm a lot less "hardware" than you, but I worked on this kit for rather over a decade. Trouble is that ended 32 years ago when Kode International (who had owned Comart for several years) went under, and a lot of water has passed under the bridge since then.

It is POSSIBLE that the sequence is that the FDC is responsible for loading the boot track to the designated address, and then the CPU jumps to it... There was no assumed standardised BIOS ROM on CP/M. The BIOS was a component of the O/S, and was shipped by each manufacturer for their hardware.
 
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Another point is that those aren't the original floppy drives.

They are IBM ones - which we never used, and so are guaranteed to be soft-sectored.

The earliest FDCs we did definitely initially only supported hard-sectored floppy drives and media - the same as the North Star Horizon. 107/2D 207/2D media instead of 104/2D 204/2D.

We later moved to supporting both, I think as a change to dual-mode drives and a firmware upgrade on the FDC. Eventually NS did too - it became the global standard after IBM, but we moved a lot earlier than NS did - it's often given as a reason for their decline.

Ultimately we completely dropped support for the hard-sectored on the later machines - the dual mode drives were getting hard to source.

You could try the later rev FDC and see if that works any better with those drives.
 
I just went out to the garage to see what I still have. Apart from a complete (supposedly working but not powered for decades) system that isn't here and was probably an 8086 or 286, I have the following:

CPU-00A Rev C Ser 1572: Switches 5 on all else off.
CPU-00A REV D Ser blank Switches all off
CPU-00A REV D Ser 3755 Switches 1 on all else off
SIO-00A REV C Ser 1396
C-RAM 64-2 MEM-04A REV B Switches @15: 0011000000 (1-10)
Switches @11: 1111001110
Switches @10: 1111111000
C-RAM 64-1 MEM-04A REV B Switches @15: 0111100000
Switches @11: 1111111110
Switches @10: 1111111110

I also have two older C-RAM MEM-00A REC B which I'm pretty sure are the original 16K RAM boards. They have different switch positions on the boards and onlyt 2 banks of switches,

I also have an HDIO-00A which could possibly drive the thing that I think is a formatter board on the left of your system, to feed into an old ST506 hard drive.

There's an old Cromemco 32K Bytesaver board lying about too - that allowed up to 32KB of EEPROM (currently socketed and unpopulated) to be programmed up with code and data and treated as a very fast way of loading the data.

In a couple of months I'll get working what I want to get working here; once that's done or I find it's impossible, all of these will be up for grabs. And possibly the main system if I can't get off it the few bits I'd like to. Or once I have done so, if the local museum don't have a good home for it.
 
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
 
Here are my Dip switch settings on the four memory cards 1 to 4 and yours a & b. There are patterns, I would guess that your cards were in single memory card systems. I will post this on a S100 forum and see if there are any suggestions.

Sw 1 (1 to 5)Sw 1 (6 to 10)Sw 2 (1 to 4)Sw2 (5 to 10)Sw3 (1 to 4)Sw3 (5 to 10)
CardADDRDMABANK ABANK B
1000000000000010000100000100010
2000100000000100000010000100001
3001000000001000000010000100001
4001100000010000000101111111110
a001100000011110011101111111110
b011110000011111111101111111110

regards Tim
 
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