handle all 4 SIDs on Mega65, tape turbo SFX should play on both left and right channels

c64/kernal/init/fda3.ioinit.s

@@ -59,10 +59,12 @@ IOINIT:
 	// Now silence the SID chip(s), depending on the configuration - we want them silent ASAP
 	//
 
-	// First the standard chip (skip if it is covered by whole $D4XX range)
-
 	lda #$00
 
+#if !CONFIG_MB_MEGA65
+
+	// First the standard chip (skip if it is covered by whole $D4XX range)
+
 #if !CONFIG_SID_D4XX
 	sta SID_SIGVOL
 #endif // !CONFIG_SID_D4XX
@@ -100,6 +102,17 @@ IOINIT:
 
 #endif // CONFIG_SID_D4XX || CONFIG_SID_D5XX
 
+#else
+
+	// Mega65 specific handling - it contains 4 SIDs
+
+	sta SID_SIGVOL + __SID_R1_OFFSET
+	sta SID_SIGVOL + __SID_R2_OFFSET
+	sta SID_SIGVOL + __SID_L1_OFFSET
+	sta SID_SIGVOL + __SID_L2_OFFSET
+
+#endif // CONFIG_MB_MEGA65
+
 	//
 	// Now continue the CIAs initialization
 	//

c64/kernal/tape/tape_common_autodetect.s

@@ -17,7 +17,12 @@ tape_common_autodetect:
 	lda #$0B
 	sta VIC_EXTCOL
 	lda #$00
+#if CONFIG_MB_MEGA65
+	sta SID_SIGVOL + __SID_R1_OFFSET
+	sta SID_SIGVOL + __SID_L1_OFFSET
+#else
 	sta SID_SIGVOL
+#endif
 
 	// FALLTROUGH
 

c64/kernal/tape/tape_common_clean_sid.s

@@ -15,7 +15,22 @@ tape_clean_sid:
 	lda #$00
 	ldy #$1C
 !:
+
+#if CONFIG_MB_MEGA65
+
+	// It should be safer than cleaning whole $D400-D47C range
+
+	sta __SID_BASE + __SID_R1_OFFSET, y
+	sta __SID_BASE + __SID_R2_OFFSET, y
+	sta __SID_BASE + __SID_L1_OFFSET, y
+	sta __SID_BASE + __SID_L2_OFFSET, y
+
+#else
+
 	sta __SID_BASE, y
+
+#endif
+
 	dey
 	bpl !-
 

c64/kernal/tape/tape_turbo_get_bit.s

@@ -23,7 +23,12 @@ tape_turbo_get_bit:
 	sta __turbo_half_S                 // store half of the last measurement result for short pulse
 
 	lda #$01
+#if CONFIG_MB_MEGA65
+	sta SID_SIGVOL + __SID_R1_OFFSET
+	sta SID_SIGVOL + __SID_L1_OFFSET
+#else
 	sta SID_SIGVOL
+#endif
 	lda #$06
 	sta VIC_EXTCOL
 	sec
@@ -34,7 +39,12 @@ tape_turbo_get_bit:
 	sta __turbo_half_L                 // store half of the last measurement result for long pulse
 
 	lda #$00
+#if CONFIG_MB_MEGA65
+	sta SID_SIGVOL + __SID_R1_OFFSET
+	sta SID_SIGVOL + __SID_L1_OFFSET
+#else
 	sta SID_SIGVOL
+#endif
 	sta VIC_EXTCOL
 	clc
 	rts