diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index 015fe5c4..8f7e32f3 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -992,8 +992,10 @@ PSCNX	.EQU	$ + 1
 ; DETERMINE WHICH CHANNEL CAUSED AN INTERRUPT.
 ;
   #IF (INTMODE == 2)
-	LD	HL,INT_TIMER
-	LD	(HBX_IVT),HL
+;
+	; TIMER INTERRUPT IS ON CTCB, VECTOR IS SECOND IVT SLOT
+	LD	HL,INT_TIMER		; TIMER INT HANDLER ADR
+	LD	(HBX_IVT + 2),HL	; IVT SLOT 2
 ;
 	; CTC USES 4 CONSECUTIVE VECTOR POSITIONS, ONE FOR
 	; EACH CHANNEL.  BELOW WE SET THE BASE VECTOR TO THE
@@ -1002,21 +1004,37 @@ PSCNX	.EQU	$ + 1
 	LD	A,0
 	OUT	(CTCBASE),A		; SETUP CTC BASE INT VECTOR
 ;
-	; CONFIGURE CHANNEL A FOR 50HZ PERIODIC INTERRUPTS
-	; INT FREQ IS CTC CLK / PRESCALER / TIME CONSTANT
+	; CTCA IS SLAVED (WIRED) TO TO CTCB TO ACT AS A PRESCALER
+	; CONFIGURE CHANNEL B FOR 50HZ PERIODIC INTERRUPTS
+	; CTC CLK = 921,200HZ
+	; CTCA TIME CONSTANT = 256
+	; CTCB TIME CONSTANT = 72
+	; INT FREQ IS CTC CLK / CTCA TC / CTCB TC
 	; WHICH IS 921,600HZ / 256 / 72 = 50HZ
-	LD	A,%10110111		; CTC CONTROL WORD VALUE
-		;  |||||||+-- 0=CONTROL WORD FLAG
+	LD	A,%01010111		; CTCA CONTROL WORD VALUE
+		;  |||||||+-- 1=CONTROL WORD FLAG
 		;  ||||||+--- 1=SOFTWARE RESET
 		;  |||||+---- 1=TIME CONSTANT FOLLOWS
 		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
 		;  |||+------ 1=RISING EDGE TRIGGER
-		;  ||+------- 1=PRESCALER OF 256
-		;  |+-------- 0=TIMER MODE
+		;  ||+------- 1=PRESCALER OF 16 (NOT USED)
+		;  |+-------- 1=COUNTER MODE
+		;  +--------- 0=NO INTERRUPTS
+	OUT	(CTCA),A		; SETUP CTCA
+	LD	A,0			; CTCA TIMER CONSTANT = 256, 0 MEANS 256
+	OUT	(CTCA),A		; SETUP CTCA TIMER CONSTANT
+	LD	A,%11010111		; CTCB CONTROL WORD VALUE
+		;  |||||||+-- 1=CONTROL WORD FLAG
+		;  ||||||+--- 1=SOFTWARE RESET
+		;  |||||+---- 1=TIME CONSTANT FOLLOWS
+		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
+		;  |||+------ 1=RISING EDGE TRIGGER
+		;  ||+------- 1=PRESCALER OF 16 (NOT USED)
+		;  |+-------- 1=COUNTER MODE
 		;  +--------- 1=ENABLE INTERRUPTS
-	OUT	(CTCA),A		; SETUP CTC CHANNEL A
-	LD	A,72			; TIMER CONSTANT FOR 50HZ
-	OUT	(CTCA),A		; SETUP CTC CHANNEL A TIMER CONSTANT
+	OUT	(CTCB),A		; SETUP CTCB
+	LD	A,72			; CTCB TIMER CONSTANT = 72
+	OUT	(CTCB),A		; SETUP CTCB TIMER CONSTANT
   #ENDIF
 ;
 #ENDIF
@@ -1029,8 +1047,10 @@ PSCNX	.EQU	$ + 1
 ; DETERMINE WHICH CHANNEL CAUSED AN INTERRUPT.
 ;
   #IF (INTMODE == 2)
-	LD	HL,INT_TIMER
-	LD	(HBX_IVT + IVT_TIM0),HL
+;
+	; TIMER INTERRUPT IS ON CTCD, VECTOR IS FOURTH IVT SLOT
+	LD	HL,INT_TIMER		; TIMER INT HANDLER ADR
+	LD	(HBX_IVT + 6),HL	; IVT SLOT 4
 ;
 	; CTC USES 4 CONSECUTIVE VECTOR POSITIONS, ONE FOR
 	; EACH CHANNEL.  BELOW WE SET THE BASE VECTOR TO THE
@@ -1039,28 +1059,40 @@ PSCNX	.EQU	$ + 1
 	LD	A,0
 	OUT	(CTCBASE),A		; SETUP CTC BASE INT VECTOR
 ;
-	; CONFIGURE CHANNEL C FOR 50HZ PERIODIC INTERRUPTS
-	; INT FREQ IS CTC CLK / PRESCALER / TIME CONSTANT
+	; CTCC IS SLAVED (WIRED) TO TO CTCD TO ACT AS A PRESCALER
+	; CONFIGURE CHANNEL D FOR 50HZ PERIODIC INTERRUPTS
+	; CTC CLK = 921,200HZ
+	; CTCC TIME CONSTANT = 256
+	; CTCD TIME CONSTANT = 72
+	; INT FREQ IS CTC CLK / CTCC TC / CTCD TC
 	; WHICH IS 921,600HZ / 256 / 72 = 50HZ
-	LD	A,%10110111		; CTC CONTROL WORD VALUE
-		;  |||||||+-- 0=CONTROL WORD FLAG
+	LD	A,%01010111		; CTCC CONTROL WORD VALUE
+		;  |||||||+-- 1=CONTROL WORD FLAG
 		;  ||||||+--- 1=SOFTWARE RESET
 		;  |||||+---- 1=TIME CONSTANT FOLLOWS
 		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
 		;  |||+------ 1=RISING EDGE TRIGGER
-		;  ||+------- 1=PRESCALER OF 256
-		;  |+-------- 0=TIMER MODE
+		;  ||+------- 1=PRESCALER OF 16 (NOT USED)
+		;  |+-------- 1=COUNTER MODE
+		;  +--------- 0=NO INTERRUPTS
+	OUT	(CTCC),A		; SETUP CTCC
+	LD	A,0			; CTCC TIMER CONSTANT = 256, 0 MEANS 256
+	OUT	(CTCC),A		; SETUP CTCC TIMER CONSTANT
+	LD	A,%11010111		; CTCD CONTROL WORD VALUE
+		;  |||||||+-- 1=CONTROL WORD FLAG
+		;  ||||||+--- 1=SOFTWARE RESET
+		;  |||||+---- 1=TIME CONSTANT FOLLOWS
+		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
+		;  |||+------ 1=RISING EDGE TRIGGER
+		;  ||+------- 1=PRESCALER OF 16 (NOT USED)
+		;  |+-------- 1=COUNTER MODE
 		;  +--------- 1=ENABLE INTERRUPTS
-	OUT	(CTCC),A		; SETUP CTC CHANNEL C
-	LD	A,72			; TIMER CONSTANT FOR 50HZ
-	OUT	(CTCC),A		; SETUP CTC CHANNEL C TIMER CONSTANT
+	OUT	(CTCD),A		; SETUP CTCD
+	LD	A,72			; CTCD TIMER CONSTANT = 72
+	OUT	(CTCD),A		; SETUP CTCD TIMER CONSTANT
   #ENDIF
 ;
 #ENDIF
-
-
-
-
 ;
 #IF ((PLATFORM == PLT_N8) | (PLATFORM == PLT_MK4) | (PLATFORM == PLT_RC180))
 ;