The original XT-IDE REV2 board has optional serial port capabilities: https://minuszerodegrees.net/xtide/rev_2/XT-I … -%20general.htm
I am not aware of another variant that offers this... be sure to read the "Optional serial port (optional 'UART')" section as it explains what the serial port does and does not.

keropi wrote on 2024-01-02, 19:40:

The original XT-IDE REV2 board has optional serial port capabilities: https://minuszerodegrees.net/xtide/rev_2/XT-I … -%20general.htm
I am not aware of another variant that offers this... be sure to read the "Optional serial port (optional 'UART')" section as it explains what the serial port does and does not.

Thanks a lot, I’m fine with both restrictions (4x faster than 'advertised' baud rate, and only RTS/CTS handshake)

Hi, some ISA modems and multi i/o cards have an 16450 in DIL/DIL form.
It can be substituted by, say, an 16550AFN chip.

I did this modification with an 286 PC which had an 16450 on-board. I've added a socket and installed the 16550AFN.

Btw, if you're trying to use it on Windows 3.1, a replacement serial port driver is recommended. Like the Cybercom driver.
The FiFo must be enabled in the system.ini to take advantage of the buffer.

More information on http://stephan.win31.de/w31mm_e1.htm

WfW 3.11 has an updated serial port driver and works good without it, too.

Good luck 🙂

PS: About the XTIDE AUX port.. Becareful it misses DTR and DSR. And the Ring Indicator RI. Edit: And DCD. 🙄
The first two were famous handshaking lines used by some DOS applications (rather than RTS/CTS).

Anyway, just saying. With a soldering iron, the missing pins for DE9 available on the 16550 could be wired manually to the pin header by jumper wires.

Edit: The use of DSR/DTR was more common in the terminal/mainframe sector, maybe.
If you're running old commercial communications software, that might be good to know.
Gamers used RTS/CTS, rather, I guess? 🤔

Edit: This one is helpful: https://stackoverflow.com/questions/957337/wh … ts-flow-control
DSR/DTR was popular up until the mid-80s.

Together with RTS/CTS they ensured that terminal-host and modem-terminal weren't overwhelmed by a flood of data.

A terminal of the time also could have been a teletype with a punch card/punch stripe reader/writer.

That way, large amounts of data from the terminal side could have overwhelmed the host computer.

That's why both pairs should be part of a modem cable or null-modrm cable, I suppose.