Based on pictures of other cards it's a UM82C11 parallel port interface IC

Must be something like 82C11, for the LPT port - https://theretroweb.com/chip/documentation/hm … 79896424556.pdf

Such I/O cards normally provide:
- LPT (parallel printer port), via 82C11
- COM (serial port), via 8250/82450
- GAME (joystick port)

Optionally, it's possible to add second 8250/82450 for second COM.

Not a big deal. My best guess is that this is an earlier version of the card and that UMC came up with a single chip solution that combined the UM8450 and the UM82C450. The other cards I see all seem to provide the same functionality with just two chips. Its just a bit strange that they all provide an empty third socket.

Also, should I technically be referring to this as an expansion board instead of a controller board?

BerkeleyGamecat wrote on 2026-04-18, 19:49:

Not a big deal. My best guess is that this is an earlier version of the card and that UMC came up with a single chip solution that combined the UM8450 and the UM82C450. The other cards I see all seem to provide the same functionality with just two chips. Its just a bit strange that they all provide an empty third socket.

They don't provide the same functionality.
two chips + empty socket = one serial port
three chips = two serial ports

Also, should I technically be referring to this as an expansion board instead of a controller board?

"I/O board" seems the most appropriate.
"Controller" usually refers to something that controls an HDD or FDD.

Thanks for the comments.

So, just to put this to rest, the 2-chip version is just a lower price option with vestigial UART headers (or maybe a jumper option to enable them instead of the DB15).

BerkeleyGamecat wrote on 2026-04-18, 22:08:

Thanks for the comments.

So, just to put this to rest, the 2-chip version is just a lower price option with vestigial UART headers (or maybe a jumper option to enable them instead of the DB15).

The 2-chip version has one serial port, with 3 chips it has two serial ports (the second one accessed via header pins). The 82450 is/are the UART(s).

Note that the card itself is identical, your pic also shows a card with two chips soldered and a third socket. The only difference is that yours has a chip in that socket.

BerkeleyGamecat wrote on 2026-04-18, 22:08:

So, just to put this to rest, the 2-chip version is just a lower price option with vestigial UART headers (or maybe a jumper option to enable them instead of the DB15).

DB15 is the joystick connector.
Serial ports use 9-pin or 25-pin connectors - in both cases you connect them to the 10-pin headers in the top-right corner.

The 2-chip version most likely was intended to be field-upgradable by installing the three missing chips, the UM82450, a MC1488 and a MC1489. A PC-type serial port requires 0.75 MC1488 chips (transmitter chip, used for TxD, RTS and DTR) and 1.25 MC1489 chips (receiver chip, used for RxD, DSR, CTS, RI and DCD), as each of these chips can process 4 signals. That's why one MC1488 and two MC1489 are already installed on the card, and you only need one extra chip of each type.

In contrast to the MAX232 commonly used today for similar purpose, the MC1488/MC1489 do not contain integrated charge pumps, but rely on externally supplied +12V and -12V. The MAX232 generates these voltages (well, more like +9.5 and -9.5) from a single +5V supply. This is why missing -12V on the ISA bus causes serial ports to fail with the remaining system still working fine, especially in an era in which there were no sound cards. that had analog amplifier chips powered by +/-12V.

Grzyb wrote on 2026-04-19, 07:07:

DB15 is the joystick connector.

Right you are. My bad.

mkarcher wrote on 2026-04-19, 09:13:

The 2-chip version most likely was intended to be field-upgradable by installing the three missing chips...

Hopefully more info then I'll ever need, but thanks for passing it along! Old info, like old hardware, deserves to be preserved.