diff --git a/Source/HBIOS/nascom.asm b/Source/HBIOS/nascom.asm
index 6b9e7297..e9f6c1da 100644
--- a/Source/HBIOS/nascom.asm
+++ b/Source/HBIOS/nascom.asm
@@ -78,7 +78,7 @@ DEL	.EQU    7FH	; Delete
 ;
 ; 0200H - 2000H	BASIC EXECUTABLE
 ; 2000H - 2090H STACK
-; 2090H - 20F8H BASIC EXECUTABLE VARAIABLES / WORKSPACE
+; 2090H - 20F8H BASIC EXECUTABLE VARIABLES / WORKSPACE
 ; 20F9H -	BASIC PROGRAM START
 
 WRKSPC  .EQU    BAS_END+90H	; BASIC Work space
diff --git a/Source/HBIOS/pio.asm b/Source/HBIOS/pio.asm
index c0d230f7..05f3e45b 100644
--- a/Source/HBIOS/pio.asm
+++ b/Source/HBIOS/pio.asm
@@ -36,7 +36,7 @@
 ;	Both port interrupt enable flip-flops are reset.
 ;	Both port output registers are reset.
 ;
-; Register addressing for ECB-ZP and ECB-4P assuming base address 90h and 88h respectively.
+; Register addressing example for ECB-ZP and ECB-4P assuming base address 90h and 88h respectively.
 ;
 ; PIO ----ZP---- ----4P----
 ;  0  DATA 0 90h DATA 0 B8h
@@ -762,7 +762,7 @@ PPI_OST:
 	RET
 ;
 ; PIO_INITDEV - Configure device.
-; If DE = FFFF then extract the configuratio information from the table of devices and program the device using those settings.
+; If DE = FFFF then extract the configuration information from the table of devices and program the device using those settings.
 ; Otherwise use the configuration information in DE to program those settings and save them in the device table
 
 PPI_INITDEV:
diff --git a/Source/HBIOS/sn76489.asm b/Source/HBIOS/sn76489.asm
index b65e9f5d..fa544064 100644
--- a/Source/HBIOS/sn76489.asm
+++ b/Source/HBIOS/sn76489.asm
@@ -15,6 +15,8 @@
 
 SN76489_PORT_LEFT	.EQU	$FC	; PORTS FOR ACCESSING THE SN76489 CHIP (LEFT)
 SN76489_PORT_RIGHT	.EQU	$F8	; PORTS FOR ACCESSING THE SN76489 CHIP (RIGHT)
+;SN76489_PORT_LEFT	.EQU	$C7	; PORTS FOR ACCESSING THE SN76489 CHIP (LEFT)
+;SN76489_PORT_RIGHT	.EQU	$C8	; PORTS FOR ACCESSING THE SN76489 CHIP (RIGHT)
 SN7_IDAT		.EQU	0
 SN7_TONECNT		.EQU	3	; COUNT NUMBER OF TONE CHANNELS
 SN7_NOISECNT		.EQU	1	; COUNT NUMBER OF NOISE CHANNELS
@@ -68,6 +70,13 @@ SN7_RESET:
 SN7_VOLUME_OFF:
 	AUDTRACE(SNT_VOLOFF)
 
+
+#IFDEF SBCV2004
+	LD	A,(RTCVAL)
+	OR	%00001000		; SBC-V2-004+ CHANGE
+	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
+#ENDIF
+
 	LD	A, CHANNEL_0_SILENT
 	OUT	(SN76489_PORT_LEFT), A
 	OUT	(SN76489_PORT_RIGHT), A
@@ -84,6 +93,12 @@ SN7_VOLUME_OFF:
 	OUT	(SN76489_PORT_LEFT), A
 	OUT	(SN76489_PORT_RIGHT), A
 
+#IFDEF SBCV2004
+	LD	A,(RTCVAL)
+	OR	%11110111		; SBC-V2-004+ CHANGE TO
+	OUT	(RTCIO),A		; NORMAL CLOCK SPEED
+#ENDIF
+
 	RET
 
 ; BIT MAPPING
@@ -237,9 +252,23 @@ SN7_APPLY_VOL:				; APPLY VOLUME TO BOTH LEFT AND RIGHT CHANNELS
 	AUDTRACE_A
 	AUDTRACE_CR
 
+#IFDEF SBCV2004
+	PUSH	AF
+	LD	A,(RTCVAL)
+	OR	%00001000		; SBC-V2-004+ CHANGE
+	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
+	POP	AF
+#ENDIF
+
 	OUT	(SN76489_PORT_LEFT), A
 	OUT	(SN76489_PORT_RIGHT), A
 
+#IFDEF SBCV2004
+	LD	A,(RTCVAL)
+	OR	%11110111		; SBC-V2-004+ CHANGE TO
+	OUT	(RTCIO),A		; NORMAL CLOCK SPEED
+#ENDIF
+
 	POP	AF
 	POP	BC
 	RET
@@ -268,9 +297,23 @@ SN7_APPLY_PRD:
 	AUDTRACE_A
 	AUDTRACE_CR
 
+#IFDEF SBCV2004
+	PUSH	AF
+	LD	A,(RTCVAL)
+	OR	%00001000		; SBC-V2-004+ CHANGE
+	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
+	POP	AF
+#ENDIF
+
 	OUT	(SN76489_PORT_LEFT), A
 	OUT	(SN76489_PORT_RIGHT), A
 
+#IFDEF SBCV2004
+	LD	A,(RTCVAL)
+	OR	%11110111		; SBC-V2-004+ CHANGE TO
+	OUT	(RTCIO),A		; NORMAL CLOCK SPEED
+#ENDIF
+
 	LD	A, L			; RIGHT SHIFT OUT THE LOWER 4 BITS
 	RRCA
 	RRCA
@@ -291,9 +334,23 @@ SN7_APPLY_PRD:
 	AUDTRACE_A
 	AUDTRACE_CR
 
+#IFDEF SBCV2004
+	PUSH	AF
+	LD	A,(RTCVAL)
+	OR	%00001000		; SBC-V2-004+ CHANGE
+	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
+	POP	AF
+#ENDIF
+
 	OUT	(SN76489_PORT_LEFT), A
 	OUT	(SN76489_PORT_RIGHT), A
 
+#IFDEF SBCV2004
+	LD	A,(RTCVAL)
+	OR	%11110111		; SBC-V2-004+ CHANGE TO
+	OUT	(RTCIO),A		; NORMAL CLOCK SPEED
+#ENDIF
+
 	POP	AF
 	POP	BC
 	POP	DE