I think most motherboards actually still support all of these crusty old GPIOs in hardware, but on a SuperIO https://en.wikipedia.org/wiki/Super_I/O https://en.

I think most motherboards actually still support all of these crusty old GPIOs in hardware, but on a SuperIO https://en.wikipedia.org/wiki/Super_I/O https://en.wikipedia.org/wiki/Super_I/O chip. One of these will usually hang off your southbridge/PCH via the Low Pin Count connector https://en.wikipedia.org/wiki/Low_Pin_Count https://en.wikipedia.org/wiki/Low_Pin_Count, which was specifically designed as the compatibility interface for these things. In a modern PC, almost none of these are used - why would anyone want to use the crummy old AT 24-bit DMA controller when you can use PCIe bus mastering - but they're there if want to boot into an old real-mode OS.