Gravis Ultrasound card ICS2101 mixer.

GUS MAX cards do not have the ICS2101 but instead use the CS4231 codec and it's mixer.


I/O ports of the ICS mixer, according to DOSBox-X source code:

BASE = Base I/O port of the GUS (typically 220h or 240h)

mixer data port = BASE + 0x106			(base 240h port 346h)
mixer address port = BASE + 0x506		(base 240h port 746h)


The ICS2101 is WRITE ONLY.

Reading either port will return a fixed value that identifies there is a mixer.

  0xFF - no mixer
  0x06 - ICS-2101 mixer (rev 3.7+)
  0x0B - UltraMax with CS4231 codec


Mixer port connections according to DOSBox-X source code:

Input port:
  0 - Mic in (R/L)
  1 - Line in (R/L)
  2 - CD in (R/L)
  3 - GF1 out (R/L)
  4 - unused (R/L)

Output goes to:
  Amp out
  Line out
  GF1 sample input

Mixer channel 5 is the Master output volume


Written and collected by Jonathan Campbell/DOSBox-X.