> The PC game port is a nearest thing to intentional GPIO that PC has.
Er, what? Not every IBM PC (clone) had a (sound) card with joystick ports, but almost every PC clone had (ISA, later PCI) extension slots. There were/are plenty of digital i/o adapter cards for those available, from plain, cheap 8255 based ones to those with slave CPUs (potentially more powerful than the host's CPU).
But then, perhaps I don't understand what you mean by 'intentional' GPIO.
Er, what? Not every IBM PC (clone) had a (sound) card with joystick ports, but almost every PC clone had (ISA, later PCI) extension slots. There were/are plenty of digital i/o adapter cards for those available, from plain, cheap 8255 based ones to those with slave CPUs (potentially more powerful than the host's CPU).
But then, perhaps I don't understand what you mean by 'intentional' GPIO.