first thought was a buffered parallel port - but there is no micro controller

the battery is missing, so considering the age, its just a memory upgrade board, with RTC and parallel.

This is a weird one to be sure... 😕

Most likely it is an EMS (expanded memory) board. This means that 1) software needs to be specifically written to work with EMS memory in order to use it, and 2) the card needs a special driver to be loaded in CONFIG.SYS for it to do anything at all. Since the Internet has apparently forgotten that this particular card ever existed, good luck finding that driver 🙁

There is an unpopulated slot for a battery on the board, which is also weird. Some EMS boards allowed you to use a portion of the memory as a RAM disk -- maybe the battery would have been for making the RAM disk persistent when powering down the system..? Possibly it's for an RTC, but where then is the RTC chip supposed to be? All the chips on the board are just generic 7400 series chips except the weird, socketed M3000-16PC in the middle of the board, which the Internet knows very little about.

Since these cards were hugely expensive, they often came with other features tacked on to sweeten the deal, so I think the 25-pin port is probably just a parallel port.

You can see similar cards being reviewed here:

https://books.google.com/books?id=hoPbDSDNLTQ … epage&q&f=false

Note that some of them come with special features: serial and parallel ports, real time clocks, even proprietary mouse ports, all kinds of stuff.

I think it's unlikely to be an EMS board. The EMS cards of that era were pretty long, until they started using SIMM slots....not to mention there is probably not enough logic on this card to make it an EMS board. There does appear to be an empty spot for a barrel type battery though, so it probably does have an RTC. RTC was rarely found on EMS boards.
I would say that it's almost certainly a 256k conventional memory upgrade board.

Anonymous Coward wrote:

I think it's unlikely to be an EMS board. The EMS cards of that era were pretty long, until they started using SIMM slots....not to mention there is probably not enough logic on this card to make it an EMS board. There does appear to be an empty spot for a barrel type battery though, so it probably does have an RTC. RTC was rarely found on EMS boards.
I would say that it's almost certainly a 256k conventional memory upgrade board.

This. Also look up the labels on the ic chips and your get a better idea of what it is.

Thanks to everyone for the feedback.

I think this card is for conventional memory, though I doubt the 41256 RAM-chips are supposed to be in it. I presume it takes 4132 chips for a total of 64 kb as stated on the sticker on the slot bracket (not shown on the picture above).

Is the metal bracket wider than the standard ones? Maybe it was intended for the original PC 5150. 64kb is a pretty pitiful upgrade.

That's why my first thought was print buffer.

I can confirm that this card has an parallel port for a print - just tested it.
As for the bracket it is standard size. What I noticed is that the sockets for the RAM-chips and the jumper do look archaic compared to other cards I have lying around.
Anyway, thanks again for all the feedback. I guess I'll remove the RAM-chips and use the card just for its parallel port.