> I have a faint memory back in the day of using the parallel port to do super speedy file transfers (compared to serial at least).

In the mid to late 90s, I was sharing my main 486's dial-up connection with an old clunky laptop using PLIP:

https://docs.kernel.org/networking/plip.html

So my brother and I could both use Netscape at the same time, on two different computers. Felt like the future!

P.S: actually the laptop was just running an X (back then not even Xorg yet) and displaying a Netscape window running on the main, beefier, PC. All over PLIP : )

LapLink!

https://www.cambus.net/file-transfers-via-the-parallel-port-...

https://en.wikipedia.org/wiki/Laplink

Ah! You got me down the right rabbit hole. I think I was actually using INTERSVR and INTERLNK but yes, must have been a LapLink cable.

https://en.wikipedia.org/wiki/List_of_DOS_commands#INTERSVR_...

That was magic for me the first time I transferred a file between computers. I didn't have to re-type my code! What a time to be alive.

Before Arduino and the analog Square reader, the parasitic-powered serial port wireless X-10 Firecracker seemed magic level to me.

https://www.x10.com/products/cm17a

The serial null modem cable with 4 ends commands you!

There is the cable used for things like LapLink and PLIP, that was inherently bitbanged. Then in theory with ECP you could connect two PCs with straight-thru cable and get something like 500Mbps with DMA support from that, on paper it was faster than both FireWire and USB HS. Whether it ever really worked is another question.