This story gets weirder and weirder by the day. Third day of testing results:
Variable changed: WS set to 1
YMF719: SetYMF continued to produce white noise in WSS testing but now a tone was actually audible behind the noise.
ES1868: Card was not detected in one ISA slot, but detected in an ISA/VLB slot. DOS installation went smooth, however ESS drivers in Windows resulted in garbled PCM audio. Removing ESS drivers and replaced them with SB1.5 drivers resulted in a working card but only FM Synth driver available was Windows default Adlib, which sucks.
OPTI929: Community driver set the card up beautifully and I managed to install official Windows 3.1 drivers. Everything worked perfectly. Until I went back to DOS and ran a game. Strangest thing: FM audio AND the game itself ran about 15% faster when I used it for FM music. 😵
SB16: Everything works perfectly.
So the SB16 is back in, and I have a theory. But first, here's a list of crystals on each card:
YMF719: 24.576MHZ, 33.8688MHz
ES1868: None
OPTI929: 24.576MHz, 16.9347MHz
SB16: 14.318MHz 24.0000MHz, 46.61512MHz
Yeah, I think that 14.318MHz is what's making the SB16 work problem free. For whatever reason, the ISA bus on this board is probably running out of spec and (well?) over 8MHz. Why, I do not know. FSB is set to 33MHz and the Bus divider is set for <=33MHz.There is, however, one header right above the 14.3MHz crystal on the motherboard market JS3 that I have no idea what it is.
Images of this board with 33MHz CPUs have that jumpered as 2-3 (here, hereand here) while mine is open (and came with a 40MHz CPU originally). So my LAST bet is to jumper that and hope stability improves and the cards actually work when the ISA frequency is resolved..
This is also probably why the VLB IO controller didn't work as well, though I'm really not keen on trying it again.
Anyway, some new theories to test tomorrow. For tonight, it's sleepy time.
Retronautics: A digital gallery of my retro computers, hardware and projects.