From d053d4b79c9d5370d2bae9f1f73ef9e5f0a1014d Mon Sep 17 00:00:00 2001
From: win2kgamer <47463859+win2kgamer@users.noreply.github.com>
Date: Fri, 30 Jan 2026 21:30:36 -0600
Subject: [PATCH] Sensation audio: Update comments
---
src/sound/snd_sensation.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/src/sound/snd_sensation.c b/src/sound/snd_sensation.c
index 4cfa7db5a..60c34de38 100644
--- a/src/sound/snd_sensation.c
+++ b/src/sound/snd_sensation.c
@@ -9,8 +9,13 @@
* Tandy Sensation 1 (25-1650)/VIS custom audio emulation.
*
* Combination of a Yamaha OPL3, MMA (YMZ263B) and the undocumented
- * VIS DAC/mixer hardware. Compatible with the "Gold Sound Standard"
- * but not fully Adlib Gold-compatible.
+ * VIS 16-bit DAC/mixer hardware. The mixer is based around a pair of
+ * Fujitsu MB87077s accessed through two sets of indexed registers on
+ * the DAC.
+ *
+ * Despite the presence of both an OPL3 and an MMA the hardware is
+ * not Adlib Gold-compatible (it lacks the EEPROM, Philips TDA8425
+ * volume/tone control and the Adlib Gold control regsisters.)
*
* Authors: Sarah Walker,
* Miran Grca,
@@ -521,9 +526,26 @@ sensation_visdac_write(uint16_t port, uint8_t val, void *priv)
visdac->visdac_regs[0x06] = val;
break;
case 0x07: /* Mixer Source Select */
+ /* Known valid source values:
+ * 0x08 = Mic
+ * 0x09 = Line
+ * 0x0A = CD
+ * 0x0B = Wave
+ * 0x0C = Phone
+ * 0x0E = MMA Wave (written when the MMA DAC is in use under Win3.1)
+ *
+ * 0x07 and 0x0F are written to this register during POST but seem unused by the drivers
+ */
visdac->visdac_regs[0x07] = val;
break;
case 0x08: /* Mixer Crossover Control */
+ /* Connects the selected source's left/right channels to the left and/or right speakers
+ * Any combination of the below values can be used:
+ * 0x05 = Route left channel to left speaker
+ * 0x10 = Route right channel to left speaker
+ * 0x28 = Route left channel to right speaker
+ * 0x42 = Route right channel to right speaker
+ */
visdac->visdac_regs[0x08] = val;
break;
case 0x09: /* Control register */