Summary

Implement the original 1989 Covox Sound Master which has an AY8930 PSG (currently implemented using Ayumi's AY-3-8910 emulation as no software uses the extended feature set), a DAC that runs in direct-drive (similar to the Speech Thing) and DMA (using channel C of the AY8930 for timing) modes and a non-standard joystick interface (not implemented) that works with Atari/Commodore-style joysticks.

The joystick interface was only supported by SimCity (and the CSM_TEST utility).

Also a few games listed as having Covox Sound Master support either lack support for this version of the hardware or shipped broken support:

• Conan the Cimmerian: Silent due to buggy sound code (sets amplitude to 0/silent).
• MegaTraveller 2: Music is missing a channel due to buggy sound code (disables channel C then tries to use it).
• The Punisher: Doesn't attempt to access any of the Sound Master registers either due to buggy sound code which is likely due to the "No Sound" option having no effect or being intended for another Covox device.

Checklist

• Closes #xxx
• I have tested my changes locally and validated that the functionality works as intended
• I have discussed this with core contributors already
• This pull request requires changes to the ROM set
  • I have opened a roms pull request - https://github.com/86Box/roms/pull/changeme/
• This pull request requires changes to the asset set
  • I have opened an assets pull request - https://github.com/86Box/assets/pull/changeme/

References

Provide links to datasheets or other documentation that helped you implement this pull request.

• Microchip AY8930 datasheet: http://map.grauw.nl/resources/sound/microchip_ay8930.pdf
• CSM_TEST source code: https://github.com/Fagear/CSM-tester
• Covox Sound Master replica Vogons thread: https://www.vogons.org/viewtopic.php?t=40512