A 'retro' BASIC 'system'

[TerryRitchie]

This might be out of topic, and too heavy for the head and the pockets:

https://www.arduino.cc/

At least to create a go-between. Find out how to make the Z-80 machine respond on board. Then try the other end of the board with the IBM PS/2.

It doesn't change the fact that there will be no 16-bit version of QB64. But QB64 could be involved somewhere with the Arduino block.

Probably Charlie was going to propose something like this. There has to be a way to make ancient equipment connect, to save them a bit longer from the junkyard.

I would love to see some work toward getting microcontrollers to communicate with QB64.

The only problem I envision with your approach is that microcontrollers, such as the Arduino, often use virtual com ports via USB meaning they can be anything above COM4. I've had Arduinos show up in the Arduino IDE as COM14 and such. Does QB64 have the ability to communicate with virtual com ports?