If you have EPROM programmer you'd better read out the ROM, the strings in it might give some hints.

I found a post about another card like this, though not much information.
https://www.amibay.com/threads/m-3000-8bit-is … 9/#post-2448925

I agree with the OP of that thread that it looks like a Hercules card. On the back of the card the PCB mask says "KT-MD3000-V2" and right under the chip on the front it says MD3000. Perhaps the MD means "Monochrome Display"? Could be Hercules + MDA... though I have no experience with either of those. It looks like the memory chips are each 64kb x 4bit, so two of them gives that card 64KB of memory. It is unlikely to be EGA-capable since most (all?) non-IBM EGA cards are 256KB. Also, it's possible that at least some of the DIP switches are meant to configure the parallel port settings, rather than display settings.

If anyone knows what that "D" logo is on the main IC though, I would love to know. I haven't been able to find it on any of the sites I usually look at for such things.

EDIT: If you google Hercules MDA ISA card you'll see tons of cards that have similar features to this. I believe we've identified what it is for. Finding the manufacturer or brand name may be impossible. Lots of devices in those days were just generic OEM-only devices.

64 KB RAM + 16.257 MHz crystal = Hercules

8 DIP switches, however, suggest some additional features - very likely there's also CGA mode.

vstrakh wrote on 2022-11-21, 07:20:

If you have EPROM programmer you'd better read out the ROM, the strings in it might give some hints.

No, it's just a character generator.

Grzyb wrote on 2022-11-21, 09:03:

No, it's just a character generator.

Ah, true for MDA. I was carried away with EGA suggestion.

8 dip switches are a lot for a pure HGC clone card. Some of the later HGC clones hat reconfigurable base address for the parallel port, but that requires at most 2 switches for the base address and 2 switches for the IRQ (one to enable IRQ5 and one to enable IRQ7). A fifth switch might switch to an alternate set of characters, but that's about it. Either the remaining 3 switches are dummy switches (just there, because switches can be bought in blocks of eight) or the card is in fact a HCG/CGA combo card, which was also common at the time. As long as you connect a multisync monitor to the card, you can safely experiment with the switches.

Thanks, everyone. A lot of good responses. I will try the card with an old 286 motherboard later this week.

It is more or less a guess but after reading this article https://www.dosdays.co.uk/topics/retro_review … cga_hgc_pt1.php it might be the case that M-3000 is rebranded 82C425 or 82C426 from Chips & Technologies. The section about DIP configuration also gives a good clue what I may expect so I am ready to experiment.