Summary

Make SB16 mixer register 82h return more accurate values based on disassembly of a 1993 version of TESTSB16.EXE, probing of a real DSP 4.11 SB16 and available documentation. This fixes 1993 TESTSB16.EXE on DSPs 4.04 and 4.05 (this version fails with an error about the card version on a real DSP 4.11 SB16).

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.

• https://the.earth.li/~tfm/oldpage/sb_mixer.html