diff --git a/Source/HBIOS/Config/MBC_std.asm b/Source/HBIOS/Config/MBC_std.asm
index 8d9fec06..ce2106b2 100644
--- a/Source/HBIOS/Config/MBC_std.asm
+++ b/Source/HBIOS/Config/MBC_std.asm
@@ -37,3 +37,5 @@ PPIDEENABLE	.SET	TRUE		; PPIDE: ENABLE PARALLEL PORT IDE DISK DRIVER (PPIDE.ASM)
 ;
 DSKYENABLE	.SET	FALSE		; ENABLES DSKY
 DSKYMODE	.SET	DSKYMODE_NG	; DSKY VERSION: DSKYMODE_[V1|NG]
+;
+CTCENABLE	.SET	FALSE		; ENABLE ZILOG CTC SUPPORT
diff --git a/Source/HBIOS/cfg_mbc.asm b/Source/HBIOS/cfg_mbc.asm
index ec23472c..ef403af0 100644
--- a/Source/HBIOS/cfg_mbc.asm
+++ b/Source/HBIOS/cfg_mbc.asm
@@ -49,7 +49,7 @@ CTCMODE		.EQU	CTCMODE_CTR	; CTC MODE: CTCMODE_[NONE|CTR|TIM16|TIM256]
 CTCPRE		.EQU	256		; PRESCALE CONSTANT (1-256)
 CTCPRECH	.EQU	2		; PRESCALE CHANNEL (0-3)
 CTCTIMCH	.EQU	3		; TIMER CHANNEL (0-3)
-CTCOSC		.EQU	614400		; CTC CLOCK FREQUENCY
+CTCOSC		.EQU	(4915200/8)	; CTC CLOCK FREQUENCY
 ;
 EIPCENABLE	.EQU	FALSE		; EIPC: ENABLE Z80 EIPC (Z84C15) INITIALIZATION
 ;
@@ -120,7 +120,7 @@ Z2UENABLE	.EQU	FALSE		; Z2U: ENABLE Z280 UART SERIAL DRIVER (Z2U.ASM)
 ;
 ACIAENABLE	.EQU	FALSE		; ACIA: ENABLE MOTOROLA 6850 ACIA DRIVER (ACIA.ASM)
 ;
-SIOENABLE	.EQU	FALSE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
+SIOENABLE	.EQU	TRUE		; SIO: ENABLE ZILOG SIO SERIAL DRIVER (SIO.ASM)
 SIODEBUG	.EQU	FALSE		; SIO: ENABLE DEBUG OUTPUT
 SIOBOOT		.EQU	0		; SIO: REBOOT ON RCV CHAR (0=DISABLED)
 SIOCNT		.EQU	1		; SIO: NUMBER OF CHIPS TO DETECT (1-2), 2 CHANNELS PER CHIP
diff --git a/Source/HBIOS/ctc.asm b/Source/HBIOS/ctc.asm
index d4c6b156..b7be79e6 100644
--- a/Source/HBIOS/ctc.asm
+++ b/Source/HBIOS/ctc.asm
@@ -101,7 +101,7 @@ CTC_PREINIT1:
 	; EACH CHANNEL.  BELOW WE SET THE BASE VECTOR TO THE
 	; START OF THE IVT, SO THE FIRST FOUR ENTIRES OF THE
 	; IVT CORRESPOND TO CTC CHANNELS A-D.
-	LD	A,0
+	LD	A,INT_CTC0A * 2
 	OUT	(CTCBASE),A		; SETUP CTC BASE INT VECTOR
 ;
 	; IN ORDER TO DIVIDE THE CTC INPUT CLOCK DOWN TO THE
diff --git a/Source/HBIOS/std.asm b/Source/HBIOS/std.asm
index 500c4fea..630d8752 100644
--- a/Source/HBIOS/std.asm
+++ b/Source/HBIOS/std.asm
@@ -670,6 +670,28 @@ INT_SIO1	.EQU	14	; ZILOG SIO 1, CHANNEL A & B
 
 ; Z80-BASED SYSTEMS
 
+
+    #IF (PLATFORM == PLT_MBC)
+
+;INT_CTC0A	.EQU	0	; ZILOG CTC 0, CHANNEL A
+;INT_CTC0B	.EQU	1	; ZILOG CTC 0, CHANNEL B
+;INT_CTC0C	.EQU	2	; ZILOG CTC 0, CHANNEL C
+;INT_CTC0D	.EQU	3	; ZILOG CTC 0, CHANNEL D
+INT_UART0	.EQU	4	; MBC UART 0
+INT_UART1	.EQU	5	; MBC UART 1
+INT_SIO0	.EQU	8	; ZILOG SIO 0, CHANNEL A & B
+INT_SIO1	.EQU	9	; ZILOG SIO 1, CHANNEL A & B
+INT_CTC0A	.EQU	12	; ZILOG CTC 0, CHANNEL A
+INT_CTC0B	.EQU	13	; ZILOG CTC 0, CHANNEL B
+INT_CTC0C	.EQU	14	; ZILOG CTC 0, CHANNEL C
+INT_CTC0D	.EQU	15	; ZILOG CTC 0, CHANNEL D
+;INT_PIO0A	.EQU	9	; ZILOG PIO 0, CHANNEL A
+;INT_PIO0B	.EQU	10	; ZILOG PIO 0, CHANNEL B
+;INT_PIO1A	.EQU	11	; ZILOG PIO 1, CHANNEL A
+;INT_PIO1B	.EQU	12	; ZILOG PIO 1, CHANNEL B
+    
+    #ELSE
+
 INT_CTC0A	.EQU	0	; ZILOG CTC 0, CHANNEL A
 INT_CTC0B	.EQU	1	; ZILOG CTC 0, CHANNEL B
 INT_CTC0C	.EQU	2	; ZILOG CTC 0, CHANNEL C
@@ -683,6 +705,8 @@ INT_PIO0B	.EQU	10	; ZILOG PIO 0, CHANNEL B
 INT_PIO1A	.EQU	11	; ZILOG PIO 1, CHANNEL A
 INT_PIO1B	.EQU	12	; ZILOG PIO 1, CHANNEL B
 
+    #ENDIF
+
   #ENDIF
 
 #DEFINE IVT(INTX) HB_IVT+(INTX * 4)+1
diff --git a/Source/ver.inc b/Source/ver.inc
index f14ca9b3..b3061a4a 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,4 +2,4 @@
 #DEFINE	RMN	1
 #DEFINE	RUP	1
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.1.1-pre.146"
+#DEFINE BIOSVER	"3.1.1-pre.147"
diff --git a/Source/ver.lib b/Source/ver.lib
index a22e049f..ade54c98 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	1
 rup	equ	1
 rtp	equ	0
 biosver	macro
-	db	"3.1.1-pre.146"
+	db	"3.1.1-pre.147"
 	endm