+ /* this is set to e.g. 0x3ff or 0x300, and writable;
+ * maybe some buffer limit, but I couldn't find out more, PU:0x00ff: */
+#define IDX_IO_SOME_VALUE 0x68
+ #define IO_68_RANDOM_TOGGLE1 0x0100 /* toggles randomly */
+ #define IO_68_RANDOM_TOGGLE2 0x0200 /* toggles randomly */
+ /* umm, nope, behaviour of these bits changes depending on what we wrote
+ * to 0x6b!!
+ * And they change upon playback/stop, too:
+ * Writing a value to 0x68 will display this exact value during playback,
+ * too but when stopped it can fall back to a rather different
+ * seemingly random value). Hmm, possibly this is a register which
+ * has a remote shadow which needs proper device supply which only exists
+ * in case playback is active? Or is this driver-induced?
+ */
+
+/* this WORD can be set to have bits 0x0028 activated (FIXME: correct??);
+ * actually inhibits PCM playback!!! maybe power management??: */
+#define IDX_IO_6AH 0x6A /* WRITE_ONLY! */
+ /* bit 5: enabling this will activate permanent counting of bytes 2/3
+ * at gameport I/O (0xb402/3) (equal values each) and cause
+ * gameport legacy I/O at 0x0200 to be _DISABLED_!
+ * Is this Digital Enhanced Game Port Enable??? Or maybe it's Testmode
+ * for Enhanced Digital Gameport (see 4D Wave DX card): */
+ #define IO_6A_SOMETHING1_GAMEPORT 0x0020
+ /* bit 8; sure, this _pauses_ playback (later resumes at same spot!),
+ * but what the heck is this really about??: */
+ #define IO_6A_PAUSE_PLAYBACK_BIT8 0x0100
+ /* bit 9; sure, this _pauses_ playback (later resumes at same spot!),
+ * but what the heck is this really about??: */
+ #define IO_6A_PAUSE_PLAYBACK_BIT9 0x0200
+ /* BIT8 and BIT9 are _NOT_ able to affect OPL3 MIDI playback,
+ * thus it suggests influence on PCM only!!
+ * However OTOH there seems to be no bit anywhere around here
+ * which is able to disable OPL3... */
+ /* bit 10: enabling this actually changes values at legacy gameport
+ * I/O address (0x200); is this enabling of the Digital Enhanced Game Port???
+ * Or maybe this simply switches off the NE558 circuit, since enabling this
+ * still lets us evaluate button states, but not axis states */
+ #define IO_6A_SOMETHING2_GAMEPORT 0x0400
+ /* writing 0x0300: causes quite some crackling during
+ * PC activity such as switching windows (PCI traffic??
+ * --> FIFO/timing settings???) */
+ /* writing 0x0100 plus/or 0x0200 inhibits playback */
+ /* since the Windows .INF file has Flag_Enable_JoyStick and
+ * Flag_Enable_SB_DOS_Emulation directly together, it stands to reason
+ * that some other bit in this same register might be responsible
+ * for SB DOS Emulation activation (note that the file did NOT define
+ * a switch for OPL3!) */
+#define IDX_IO_6CH 0x6C /* unknown; fully read-writable */
+#define IDX_IO_6EH 0x6E
+ /* writing 0xffff returns 0x83fe (or 0x03fe only).
+ * writing 0x83 (and only 0x83!!) to 0x6f will cause 0x6c to switch
+ * from 0000 to ffff. */