I became aware of the SN76489 through the "Tandy 3 Voice Sound - SN76489 ISA Soundcard Project" (https://www.vogons.org/viewtopic.php?t=54249). Since it only has write registers, it is well suited for extension to lb3361 extension-retro.
I started making a sound card for this extension. I will continue to report on progress. My attempts so far can be found here: https://github.com/hans61/Gigatron-TTL/ ... und%20card
gigatron-sn76489-schematic.png (28.2 KiB) Viewed 762 times
20220806-gigatron-soundcard.jpg (179.9 KiB) Viewed 762 times
Outstanding! I didn't get what you meant by "it is well suited for extension to lb3361 extension-retro" until I saw the photo in the Pluggy Reloaded thread showing how the headers lined up. Looking forward to your updates!
I recommend using a crystal with a frequency of 3.57mhz or lower, because for the SN76489, a lower crystal frequency allows a lower tone. For example, the lowest sound of SN76489 at 3.57mhz is A2.
Since I have developed many MegaMods (vintage Yamaha FM synth music IC modules) before, I can even launch sound cards for gigatron with many FM sources, such as YM2612, YM2151, YM2203, etc. But lack of software support, even if I made the hardware out, it would take a lot of time to write the music driver.
.