Hello, I'm very interested in the old Yamaha soundchips for a personal project of mine.
I'm somewhat familiar with the inner workings of the OPL chips, as there is tons of documentation on them, ranging from reference manuals to reverse engineered ICs (though of course, hard to understand because of the complexity). According to my knowledge, these chips would output their data as serial data, which then needs to be processed by another chip, that would also convert the signal from digital to analog (DAC). However, it's very hard to find any information on the typically used DAC chips aside from reference manuals. I'm talking about the YAC-51X chips, such as the YAC-516, which is used for the OPL-4 soundchips for example. Were these chips used in soundblaster cards (or derivatives) as well or did these cards implement a custom solution for the task of converting the digital audio to analog audio? And how did the mixing work in those chips? Were they just adding the signals together and then hard clip the resulting audio or was there some kind of compression or soft clipping involved? Was there any other post-processing? I know that some DACs oversample and then apply a filter for frequencies above 20 kHz to avoid aliasing.
Another curiousity is the PCM capability of the OPL-4 soundchip. It was possible to connect an external ROM or RAM to it, to directly play samples from it. However, I found little information on the access times of said external memory (of the chip itself I mean, not the interface on the chip which is accessed via CPU).
Does anybody here know more about this or can point me to a place where there is more information about it?