Except that wasn't a serial port, it was midi, and the reason it was on the sound card was because the input was analog.

Your joystick was just two fancy potentiometers, and your soundcard decoded the voltage on the middle legs into a position.

Soundcards handled joysticks because they had the fastest ADCs.

Early PC only had 5 card slots, and the only jack on the motherboard was the keyboard. One slot is going to be used by a video card, one’s probably being used by a hard drive controller, one’s probably used by a parallel + serial card. Soundcards also included controller ports to try to save a slot.

And because the PC only have 1 serial port, you disconnect the printer and use a parallel to serial adapter.

@josefo@leminal.space @JoMiran@lemmy.ml

Technically speaking, the joystick involved analog voltages to be converted to digital signals... And what else have ADC (analog-to-digital converters) chips? Soundcards, because ADCs are used to convert mic input, alongside the "line in", both of which are analog voltages, into PCM signals, which are discrete (as in "non-continuous") streams of bits. Something inverse happens for "headphone", "speakers" and "line out" pins: a PCM stream coming from the sound driver is converted to analog voltages using a DAC.

While other ports also happened to deal with analog<->digital conversion, a soundcard was particularly specialized at this job, alongside graphic (VGA) cards (VGA has lots of analog signals), but graphic cards were already too busy with thousands/millions of pixels and, well, with computation of graphics.

Other boards aren't so fitting for analog-digital job. For example: a NIC (Network Interface Card) already deals with digital signal so, theoretically, no conversion is necessary from/to analog. Parallel ports (those for printers) also natively deals with digital signals. Expansion cards with USB ports, same thing. And so on...

(Apologies for my blank reply if my deletion didn't federate due to insufficient Sharkey-Lemmy federation, I mistyped enter as I was getting ready to write my message)

And because the PC only have 1 serial port, you disconnect the printer and use a parallel to serial adapter.