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View Full Version : Which kind of bus is this MDA card intented for?



Rauli
May 23rd, 2017, 01:42 PM
I post a photo of the latest card I got: 38751

It's just a regular MDA/parallel clone... except for the bus connector. It should be 8-bit ISA, but it has the 16-bit ISA extension and a 2nd very strange (and unknown for me) extension.

More details about the card:
- External connectors are DB-9 and DB-25 (both female).
- Looks like MDA/Parallel or Hercules/Parallel
- Newest chip is dated 8731
- Chips include a 6845 (CTRC), two TMM2016 (RAM), and a stickered chip with UV window (EPROM or micro-controller).
- Smaller ones are just 74LS and PALs (the stickered ones).
- According to datasheet each RAM chip is 2 Kbytes, so not Hercules/Parallel, but MDA/Parallel.

What do you think about it? Did you know about the existance of such connector?

Note: I got replies in other forums claiming it's a VESA Local Bus connector. IT IS NOT. The VLB extension has narrow fingers, the same width than PCI connector fingers. This card 2nd extension fingers are the same width than the 8-bit and 16-bit ISA connector fingers.

Note 2: The big stickered chip turned out to be an 4 Kbyte EPROM with characters definitions (nothing else, no BIOS or such).

keenerb
May 23rd, 2017, 02:43 PM
I post a photo of the latest card I got: 38751

It's just a regular MDA/parallel clone... except for the bus connector. It should be 8-bit ISA, but it has the 16-bit ISA extension and a 2nd very strange (and unknown for me) extension.

More details about the card:
- External connectors are DB-9 and DB-25 (both female).
- Looks like MDA/Parallel or Hercules/Parallel
- Newest chip is dated 8731
- Chips include a 6845 (CTRC), two TMM2016 (RAM), and a stickered chip with UV window (EPROM or micro-controller).
- Smaller ones are just 74LS and PALs (the stickered ones).
- According to datasheet each RAM chip is 2 Kbytes, so not Hercules/Parallel, but MDA/Parallel.

What do you think about it? Did you know about the existance of such connector?

Note: I got replies in other forums claiming it's a VESA Local Bus connector. IT IS NOT. The VLB extension has narrow fingers, the same width than PCI connector fingers. This card 2nd extension fingers are the same width than the 8-bit and 16-bit ISA connector fingers.

Note 2: The big stickered chip turned out to be an 4 Kbyte EPROM with characters definitions (nothing else, no BIOS or such).

The J3 connector looks a little odd also.

Possibly an industrial board. Is J3 connected directly to the extra card edge connector?

Rauli
May 23rd, 2017, 03:07 PM
Is J3 connected directly to the extra card edge connector?

Yes! The 3 P3 fingers seen in the photo, go to one of the PALs and also go to J3.

The 2 P3 fingers on the other side of the card: One goes to the jumper block U16 (*) and I can't trace the other one.

(*) I don't know what this jumpers do. I expected they change the LPT port address or IRQ, but they don't. And I don't know which other thing can be configured on an MDA/parallel card.

Chuck(G)
May 23rd, 2017, 04:26 PM
My guess is that this board can be operated as a 16-bit MDA card, making screen writing much faster. The extra traces on J3 are a mystery.

Have you tried this card in an 8-bit slot to see if it works as a normal 8-bit MDA card? Clearly, there's not enough memory here to do graphics.

Rauli
May 23rd, 2017, 10:11 PM
My guess is that this board can be operated as a 16-bit MDA card, making screen writing much faster. The extra traces on J3 are a mystery.

Yes, but I don't know if both 2 Kbyte RAM chips are arranged as 4 Kbytes, or as 2 Kwords (storing separately even and odd addresses). Only the last case could benefit from 16-bit access mode. Is there any tool to measure video memory speed in both 8-bit and 16-bit access? Like VGASPEED but for MDA, and not requiring a 386.


Have you tried this card in an 8-bit slot to see if it works as a normal 8-bit MDA card? Clearly, there's not enough memory here to do graphics.

Well, my monochrome screen is not at home, so I tried the card blindly (no screen) alone and also as a secondary video adapter (together with a VGA), but on an 16-bit ISA slot. All I can say is that all sysinfo tools detect the card as an MDA. Next test will be on an 8-bit ISA slot, and later with the monochrome screen.

Chuck(G)
May 23rd, 2017, 10:21 PM
If I were the designer, I'd use the RAMs as 16-bit wide; even addresses: character, odd addresses: attribute. I doubt that either organization would be sub-ISA bus speed, so 16-bit access should be roughly twice the speed of an 8 bit only card.

Xacalite
May 24th, 2017, 06:42 AM
What's the actual speed of 8-bit ISA? Something like 1 MB/s, isn't it?
For a 4 KB frame buffer, it gives 250 fps.
Who needs more, especially considering MDA's refresh rate is only 50 Hz?

keenerb
May 24th, 2017, 07:19 AM
Was there potentially a graphical overlay from another proprietary display adapter, fed in on the J3 connector?

From an old high-end CAD system, or something...

That's a pretty unique card. I hope you figure it out, and once you do I hope you let us know!

Chuck(G)
May 24th, 2017, 07:54 AM
What's the actual speed of 8-bit ISA? Something like 1 MB/s, isn't it?
For a 4 KB frame buffer, it gives 250 fps.
Who needs more, especially considering MDA's refresh rate is only 50 Hz?

Scrolling is a big problem on PC text displays. Look at the BIOS code. Using a REP MOVSB is pretty slow. A REP MOVSW on a 16-bit CPU would be considerably faster. If you've got an MDA, try echoing the data from a 9600 bps feed. The move-memory scrolling can't keep up.

Some comms package got smart and changed the "start address" for the 6845 and allowed the buffer to "wrap around" the display memory, but that wasn't what was used in the IBM BIOS to scroll. In particular, the "Print Screen" function didn't work right. Others just buffered up data until they caught a break, then updated the screen.

Rauli
May 24th, 2017, 02:43 PM
Was there potentially a graphical overlay from another proprietary display adapter, fed in on the J3 connector?

From an old high-end CAD system, or something...

I don't think the card has the required circuitry to treat overlays. Not sure, but I think it would need more than 74LSs and old PALs.


That's a pretty unique card. I hope you figure it out, and once you do I hope you let us know!

I also hope it, thanks, but I'm more interested in the kind of bus, than in the card itself :p

Rauli
May 24th, 2017, 02:54 PM
What's the actual speed of 8-bit ISA? Something like 1 MB/s, isn't it?
For a 4 KB frame buffer, it gives 250 fps.

I think it's 8 Mbytes/s. But a 0-wait-state memory access takes 4 cycles to a 8088/8086 (at 4.77 or 8 MHz).

Xacalite
May 24th, 2017, 03:33 PM
I think it's 8 Mbytes/s. But a 0-wait-state memory access takes 4 cycles to a 8088/8086 (at 4.77 or 8 MHz).
Which means that for practical purposes it's more like 1 MB/s.
More info: http://www.vcfed.org/forum/showthread.php?56463-ISA-maximum-sustained-transfer-rate

geoffm3
May 25th, 2017, 10:59 AM
Granted I've never seen any card like this before, but perhaps it was meant to go in an Amiga 2000? The additional card edge would certainly line up in the overlapped Zorro/ISA bus slots.

geoffm3
May 25th, 2017, 11:00 AM
Any other markings on the back of the card? Otherwise, I'd say dump the ROM and maybe there's a clue in there.

vwestlife
May 25th, 2017, 11:38 AM
It almost looks like the additional card edge connector was only meant for testing a prototype, and was intended to be snapped off on the production version.

glitch
May 25th, 2017, 11:47 AM
I've seen a little card edge connector behind an ISA slot in...I want to say a Compaq Deskpro system? Might've even been 6-pin. I never figured out what it was for, the ISA slot was otherwise normal.

Rauli
May 25th, 2017, 12:53 PM
Granted I've never seen any card like this before, but perhaps it was meant to go in an Amiga 2000? The additional card edge would certainly line up in the overlapped Zorro/ISA bus slots.

The card seems to be manufactured in 1987. The card works in a PC using just the ISA-8 and ISA-16 part, leaving the strange extension unconnected. I'm not in the Amiga world, but with this information, could it still be an Amiga Zorro card?

Rauli
May 25th, 2017, 12:58 PM
Any other markings on the back of the card? Otherwise, I'd say dump the ROM and maybe there's a clue in there.

Nothing but a sequence of letter+numbers (I will look again and take note).

I dumped the ROM, it contains character definitions, no more. That's the only information MDA and Hercules cards need to know. The PC BIOS knows how to handle these video cards (and CGA, too).

Rauli
May 25th, 2017, 10:05 PM
I've seen a little card edge connector behind an ISA slot in...I want to say a Compaq Deskpro system? Might've even been 6-pin. I never figured out what it was for, the ISA slot was otherwise normal.

Do you mean you've seen a similar bus connector (like P1+P2+P3 connector parts) or a similar pin connector (like J3)? That angle-pin connectors are not unusual where there's not much space and straight pins can't be used. I've seen the same, for example, inside keyboards, where the cable is connected.

Rauli
May 25th, 2017, 10:09 PM
Granted I've never seen any card like this before, but perhaps it was meant to go in an Amiga 2000? The additional card edge would certainly line up in the overlapped Zorro/ISA bus slots.

Apart of mechanically compatible, definitely not a Zorro card. I got the Zorro bus specification and the address and data lines are in very different position than ISA bus. If it were a Zorro card, it wouldn't have worked in my PC.

So the title question is still unanswered.

keenerb
May 26th, 2017, 04:59 AM
Do you mean you've seen a similar bus connector (like P1+P2+P3 connector parts) or a similar pin connector (like J3)? That angle-pin connectors are not unusual where there's not much space and straight pins can't be used. I've seen the same, for example, inside keyboards, where the cable is connected.

Some Compaq modem/audio combo cards from the 90's/early 2000's had an extra ISA J3 connector. I forgot about that, I even have a few.

http://i.ebayimg.com/images/g/26sAAOSwhQhYyc23/s-l1600.jpg

That's an example.

Sadly not the same bus, the spacing/size is completely different.

keenerb
May 26th, 2017, 05:03 AM
Nothing but a sequence of letter+numbers (I will look again and take note).

I dumped the ROM, it contains character definitions, no more. That's the only information MDA and Hercules cards need to know. The PC BIOS knows how to handle these video cards (and CGA, too).

Can't PAL chips be decoded now? Maybe something could be derived from the pal that's in-line with the card-edge connector and the pins.

glitch
May 26th, 2017, 05:22 AM
Do you mean you've seen a similar bus connector (like P1+P2+P3 connector parts) or a similar pin connector (like J3)? That angle-pin connectors are not unusual where there's not much space and straight pins can't be used. I've seen the same, for example, inside keyboards, where the cable is connected.

I meant the P3 connector, keenerb's sound card is what I remember the connector looking like.


Some Compaq modem/audio combo cards from the 90's/early 2000's had an extra ISA J3 connector. I forgot about that, I even have a few.

Sadly not the same bus, the spacing/size is completely different.

Ah, thanks for the clarification! I remembered it looked similar, but I no longer have a machine with the extra connector to check. I don't think I ever had a card that utilized it.

Xacalite
May 26th, 2017, 06:22 AM
What's the purpose of that extra connector in Compaq?

BTW, there were plenty of 386 boards with proprietary memory expansion slots, see eg. http://stason.org/TULARC/pc/motherboards/M/MICRONICS-COMPUTERS-INC-386-80386-SMT-ASIC-386-ASI.html
However, such extra slots implemented 32-bit bus, ie. were much longer than P3 in that MDA.

evildragon
May 26th, 2017, 06:59 AM
I know it can't be a deskpro since the spacing is different, but it looks like on the deskpro the size wouldn't have mattered because that extra connector is open, so a larger connector could fit in.

https://cdn6.bigcommerce.com/s-a1x7hg2jgk/images/stencil/1280x1280/products/9892/49936/compaq-deskpro-4000-backplane-board-3-isa-1-pci-270882-001-1.39__35321.1490001741.jpg?c=2

geoffm3
May 26th, 2017, 07:34 AM
Apart of mechanically compatible, definitely not a Zorro card. I got the Zorro bus specification and the address and data lines are in very different position than ISA bus. If it were a Zorro card, it wouldn't have worked in my PC.

So the title question is still unanswered.

Yeah, just looked at it and on those pin positions you have power and ground on a Zorro II/III slot.

geoffm3
May 26th, 2017, 07:36 AM
Any FCC ID markings and have you traced where the signals go?

6885P5H
May 26th, 2017, 10:30 AM
Some PC manufacturers came up with their own short-lived 32-bit ISA bus like Olivetti. This card might have come from such a PC.

vwestlife
May 26th, 2017, 12:51 PM
Some PC manufacturers came up with their own short-lived 32-bit ISA bus like Olivetti. This card might have come from such a PC.

But not in 1987, when this card is from...

I think it might be from some kind of industrial backplane system.

6885P5H
May 26th, 2017, 01:45 PM
Actually yes, it was in 1987 that Olivetti released their M380 systems, which featured 32-bit ISA slots.
http://fr.1001mags.com/parution/svm/numero-42-septembre-1987/page-74-75-texte-integral
Translation: The Olivetti M380 is a machine that's made for the desktop. It features 7 expansion slots, 3 of them able to be used to connect cards on an extended 32-bit bus.
http://www.supervinx.com/OnlineMuseum/Olivetti/M380-XP5/Inner/004-04300024.JPG
I think memory cards, video cards and disk controllers were made for these slots. This card does not look like it was made by Olivetti, and I doubt anyone other than them made cards for their 32-bit ISA slots, but maybe another manufacturer somewhere also came up with their own 32-bit ISA slots in 1987... Or maybe not, but it's a possibility, right?

Rauli
May 27th, 2017, 05:51 AM
Some Compaq modem/audio combo cards from the 90's/early 2000's had an extra ISA J3 connector. I forgot about that, I even have a few.

That's an example.

Sadly not the same bus, the spacing/size is completely different.

But interesting, like mine :)
I wonder what the extra connector is for. Could it send sound output to the mainboard for... maybe... front panel connectors? Or, send sound to mainboard buzzer?
I know, connecting front panel jacks to sound card is much easier than connecting front panel jacks to mainboard and mainboard to soundcard via non-standard ISA connector, but I can't figure out another function for this...

Rauli
May 27th, 2017, 05:59 AM
BTW, there were plenty of 386 boards with proprietary memory expansion slots, see eg. http://stason.org/TULARC/pc/motherboards/M/MICRONICS-COMPUTERS-INC-386-80386-SMT-ASIC-386-ASI.html
However, such extra slots implemented 32-bit bus, ie. were much longer than P3 in that MDA.

Yes, there were such memory expansion slots. What I don't know is, if the memmory slot is the ISA-16 part + the extension, or just the extension. In the board of your link I don't know if they form just one slot... or 2 aligned but different slots.


Any FCC ID markings and have you traced where the signals go?

No FCCID but there are some markings in the backside. I will post a photo.


Can't PAL chips be decoded now? Maybe something could be derived from the pal that's in-line with the card-edge connector and the pins.

I have an EPROM reader/writer. It can be used to read a few GALs, but no PALs.

Rauli
May 27th, 2017, 06:05 AM
I know it can't be a deskpro since the spacing is different, but it looks like on the deskpro the size wouldn't have mattered because that extra connector is open, so a larger connector could fit in.

It's seems where the previous sound card should be connected...
What's curious is that this raiser card has an "AUDIO OPT" connector, and another one which is not mounted. I wonder if the ISA 6-pin extra connector goes to those "AUDIO OPT" connectors.

Rauli
May 27th, 2017, 06:08 AM
38824
All the markings on the backside of the card:

"KS-2" together with a kind of logo
AVL triangle
P1864-03 REV B

Chuck(G)
May 27th, 2017, 10:00 AM
The "AVL" would seem to be a good hint. Audio-Visual Laboratories, the parent of the Eagle computer line--but not necessarily a computer manufacturer themselves. They produced graphics systems for the PC-AT, for example.

I wonder if an old timer on the AVSForum might recognize the card.

Rauli
May 27th, 2017, 01:04 PM
The "AVL" would seem to be a good hint. Audio-Visual Laboratories, the parent of the Eagle computer line--but not necessarily a computer manufacturer themselves. They produced graphics systems for the PC-AT, for example.

I wonder if an old timer on the AVSForum might recognize the card.

Oh, is it a company logo? I mistook it with the 3-letter triangle embossed on many plugs... but I have just taken a look right now and letters in plugs are "DVE"... sorry :ashamed2:

Rauli
June 3rd, 2017, 10:21 AM
After browsing many photos of AVL (Audio Visual Laboratories) new and old products, I think this "AVL in triangle" has nothing to do with that company :sad:

g4ugm
June 4th, 2017, 08:57 AM
Nothing but a sequence of letter+numbers (I will look again and take note).

I dumped the ROM, it contains character definitions, no more. That's the only information MDA and Hercules cards need to know. The PC BIOS knows how to handle these video cards (and CGA, too).

No FCC ID any where to give a clue to the maker?

Rauli
June 4th, 2017, 11:46 AM
No FCC ID any where to give a clue to the maker?

Nothing that you can't see in the photos. I didn't hide anything, I promise ;)

vwestlife
June 4th, 2017, 05:02 PM
It might have been made for an industrial rack-mount computer with a built-in monitor. You'd have to probe the pins of the extra card-edge connector when it's powered on to see what kind of signals are on them.

evildragon
June 4th, 2017, 05:22 PM
I think honestly, at this point, just plugging in the card, and dumping the ROM with a utility will be best in figuring out who makes the card.

Rauli
June 5th, 2017, 02:37 AM
I think honestly, at this point, just plugging in the card, and dumping the ROM with a utility will be best in figuring out who makes the card.

The CPU has no access to the ROM, it's not in the same address space. But I read it with an EPROM burner, and it just contains character definitions. It has no executable code or any other data or copyright. Only character definitions.

Chuck(G)
June 5th, 2017, 07:54 AM
Have you traced the data lines from the P2 connector to see if they're actually connected to something?