Right, a GPIO interface would be more of an exercise in old digital stuff, given that the same result could be achieved on a single uC.
Long time ago I though of doing a YM2151 FM synth chip card, like the Adlib, but then someone else already got to it; it's on the texelec website. So I just built a microcontroller board around that synth chip instead, to play VGM files from an SD card.
Got somewhat lucky growing up, my parents never made me completely throw away old PC stuff from the 90's. I had lots of hand-me-down computer stuff from the 80's and early 90's. They even let me store it there during most of my 20's years. Things in life started to settle down by the time I was hitting 30, so I lugged all that old computer stuff over to my own place. Then things kind of got out of control from there... really got into old computers... last I counted 17 CRT monitors.
Long time ago I though of doing a YM2151 FM synth chip card
Wow, you just jogged my memory about another project I wanted to do as a PC add-on card. I recovered an Ensoniq "Q" chip from an Apple IIgs motherboard that I picked up a repair shop salvage in the late 80s. The Q chip is the main sound device from the Ensoniq ESQ-1 synthesizer and I think it was also used in the Ensoniq Mirage DSK-8 sampling keyboard.
The Q chip was a very powerful sound chip for the time and was designed by the same guy who did the SID chip in the Commodore 64. I struggled to get a datasheet for the Q chip to build a sound card/synth on a PC card project so I held onto the Q chip. I still have it and data is now available for it. That might make an interesting project, but I would probably just use a microcontroller or rPI to avoid having to write convoluted drivers in X86 assembly.
Maybe I'll look at that idea again since I still have the chip. I already have some Ensoniq synthesizers (SD-1 and SQ-80) so maybe it's not really worth it but it could be fun and frustrating to try.
If you do get into that, let me know how it goes. That's a cool little sound chip.
I have a ROM 01 Apple IIgs, spare motherboard, spare monitor. Love that machine. More or less same CPU as the SNES. Stuck one of those ReActive Micro Transwarp clone accelerator cards in there, drives it up to 16 MHz.
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