Hi all,

I would like to know if there is any way to add GPIO functionality to a Linux PC (not a Raspberry PI). Imagine an old DOS machine where one could read and write bits to the parallel port. That's what I want to do, but with a modern PCIE card of some sort. 8 bits would be good enough, but I'll gladly take more

Also, I wonder if a PCIE parallel port card would do it. How would I access individual bits of the card. I'm sure I can't just peek and poke memory addresses using a modern protected mode OS (Debian 11, 64 bit).

I have been using an FTDI232RL in bitbang mode and it works, but it's slow and cumbersome to use (I have to build up a data stream with bits set or cleared, then send the bytes to the FTDI to turn individual bits on or off. Reading data lines is even more of a pain).

Any suggestions will be greatly appreciated!

There are lots of options including USB just depends on your requirements and budget. They typically have their own drivers etc. Here are just a few:
National Instruments
Advantech
MCCDAQ
adlink technology

Does it have to be a pc? They're about the worst thing to do gpio on.

If not, use something else. If you need a pc, check out accessories for Industrial PCs. You might get something that will plug into usb or take a slot.

Python with pyparallel package may be a suitable solution for GPIO over parallel port.

https://pypi.org/project/pyparallel/