diff --git a/Source/HBIOS/cfg_RCEZ80.asm b/Source/HBIOS/cfg_RCEZ80.asm
index 2f3e67f4..e0f62b97 100644
--- a/Source/HBIOS/cfg_RCEZ80.asm
+++ b/Source/HBIOS/cfg_RCEZ80.asm
@@ -379,11 +379,11 @@ UFENABLE	.SET	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.SET	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
 AUDIOTRACE	.SET	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
-SN7CLK		.SET	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
+SN7CLK		.SET	CPUOSC/4	; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.SET	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM|DUO]
 ;
 AY38910ENABLE	.SET	FALSE		; AY: ENABLE AY-3-8910 / YM2149 SOUND DRIVER
-AY_CLK		.SET	1789772		; AY: PSG CLOCK FREQ, ASSUME MSX STD
+AY_CLK		.SET	CPUOSC/4	; AY: PSG CLOCK FREQ, ASSUME MSX STD
 AYMODE		.SET	AYMODE_RCZ80	; AY: DRIVER MODE: AYMODE_[SCG|N8|RCZ80|RCZ180|MSX|LINC|MBC|DUO|NABU]
 ;
 SPKENABLE	.SET	FALSE		; SPK: ENABLE RTC LATCH IOBIT SOUND DRIVER (SPK.ASM)
diff --git a/Source/HBIOS/sn76489.asm b/Source/HBIOS/sn76489.asm
index 8a41fe7d..c6e8c42c 100644
--- a/Source/HBIOS/sn76489.asm
+++ b/Source/HBIOS/sn76489.asm
@@ -87,6 +87,7 @@ SN7_INIT:
 #IFDEF SBCV2004
 	LD	A,(HB_RTCVAL)
 	OR	%00001000		; SBC-V2-004+ CHANGE
+	EZ80_IO
 	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
 #ENDIF
 ;
@@ -95,13 +96,16 @@ SN7_INIT:
 SN7_INIT1
 	LD	A,(HL)
 	INC	HL			; BUMP FOR NEXT TIME
+	EZ80_IO
 	OUT	(SN76489_PORT_LEFT), A	; WRITE LEFT PORT
+	EZ80_IO
 	OUT	(SN76489_PORT_RIGHT), A	; WRITE RIGHT PORT
 	DJNZ	SN7_INIT1		; LOOP TILL DONE
 ;
 #IFDEF SBCV2004
 	LD	A,(HB_RTCVAL)
 	AND	%11110111		; SBC-V2-004+ CHANGE TO
+	EZ80_IO
 	OUT	(RTCIO),A		; NORMAL CLOCK SPEED
 #ENDIF
 ;
@@ -288,16 +292,19 @@ SN7_APPLY_VOL:				; APPLY VOLUME TO BOTH LEFT AND RIGHT CHANNELS
 	PUSH	AF
 	LD	A,(HB_RTCVAL)
 	OR	%00001000		; SBC-V2-004+ CHANGE
+	EZ80_IO
 	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
 	POP	AF
 #ENDIF
-
+	EZ80_IO
 	OUT	(SN76489_PORT_LEFT), A
+	EZ80_IO
 	OUT	(SN76489_PORT_RIGHT), A
 
 #IFDEF SBCV2004
 	LD	A,(HB_RTCVAL)
 	AND	%11110111		; SBC-V2-004+ CHANGE TO
+	EZ80_IO
 	OUT	(RTCIO),A		; NORMAL CLOCK SPEED
 #ENDIF
 
@@ -333,16 +340,19 @@ SN7_APPLY_PRD:
 	PUSH	AF
 	LD	A,(HB_RTCVAL)
 	OR	%00001000		; SBC-V2-004+ CHANGE
+	EZ80_IO
 	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
 	POP	AF
 #ENDIF
-
+	EZ80_IO
 	OUT	(SN76489_PORT_LEFT), A
+	EZ80_IO
 	OUT	(SN76489_PORT_RIGHT), A
 
 #IFDEF SBCV2004
 	LD	A,(HB_RTCVAL)
 	AND	%11110111		; SBC-V2-004+ CHANGE TO
+	EZ80_IO
 	OUT	(RTCIO),A		; NORMAL CLOCK SPEED
 #ENDIF
 
@@ -370,16 +380,19 @@ SN7_APPLY_PRD:
 	PUSH	AF
 	LD	A,(HB_RTCVAL)
 	OR	%00001000		; SBC-V2-004+ CHANGE
+	EZ80_IO
 	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
 	POP	AF
 #ENDIF
-
+	EZ80_IO
 	OUT	(SN76489_PORT_LEFT), A
+	EZ80_IO
 	OUT	(SN76489_PORT_RIGHT), A
 
 #IFDEF SBCV2004
 	LD	A,(HB_RTCVAL)
 	AND	%11110111		; SBC-V2-004+ CHANGE TO
+	EZ80_IO
 	OUT	(RTCIO),A		; NORMAL CLOCK SPEED
 #ENDIF