diff --git a/Source/HBIOS/acia.asm b/Source/HBIOS/acia.asm
index 58d6ec0d..7cfb5691 100644
--- a/Source/HBIOS/acia.asm
+++ b/Source/HBIOS/acia.asm
@@ -27,9 +27,25 @@ ACIA_ACIA	.EQU	1
 ACIAA_BASE	.EQU	$80 + $20	; MODULE A
 ACIAB_BASE	.EQU	$40 + $20	; MODULE B
 ;
+#IF (INTMODE == 0)
+;
+ACIA_RTSON	.EQU	%00010110	; NO RCV INT, RTS ASSERTED, 8N1, CLK/64 BAUD
+ACIA_RTSOFF	.EQU	%01010110	; NO RCV INT, RTS DEASSERTED, 8N1, CLK/64 BAUD
+;
+#ENDIF
+;
+#IF (INTMODE == 1)
+;
 ACIA_RTSON	.EQU	%10010110	; RCV INT, RTS ASSERTED, 8N1, CLK/64 BAUD
 ACIA_RTSOFF	.EQU	%11010110	; RCV INT, RTS DEASSERTED, 8N1, CLK/64 BAUD
 ;
+#ENDIF
+
+#IF (INTMODE > 1)
+	.ECHO	"*** ERROR: UNSUPPORTED INTMODE FOR ACIA DRIVER!!!\n"
+	!!!	; FORCE AN ASSEMBLY ERROR
+#ENDIF
+;
 ;
 ;
 ACIA_PREINIT:
@@ -55,7 +71,7 @@ ACIA_PREINIT0:
 	POP	DE			; GET ENTRY ADDRESS BACK, BUT PUT IN DE
 	POP	BC			; RESTORE LOOP CONTROL
 ;
-	LD	A,(IY + 1)		; GET THE ACIA TYPE DETECTED
+	LD	A,(IY+1)		; GET THE ACIA TYPE DETECTED
 	OR	A			; SET FLAGS
 	JR	Z,ACIA_PREINIT2		; SKIP IT IF NOTHING FOUND
 ;	
@@ -75,7 +91,7 @@ ACIA_PREINIT2:
 ;
 ACIA_INITUNIT:
 	CALL	ACIA_DETECT		; DETERMINE ACIA TYPE
-	LD	(IY + 1),A		; SAVE IN CONFIG TABLE
+	LD	(IY+1),A		; SAVE IN CONFIG TABLE
 	OR	A			; SET FLAGS
 	RET	Z			; ABORT IF NOTHING THERE
 
@@ -84,7 +100,8 @@ ACIA_INITUNIT:
 	LD	A,(HL)			; PUT IN ACCUM
 	INC	(HL)			; INCREMENT IT (FOR NEXT LOOP)
 	LD	(IY),A			; UDPATE UNIT NUM
-
+;
+#IF (INTMODE == 1)
 	; ADD IM1 INT CALL LIST ENTRY
 	LD	L,(IY+6)		; GET RCVBUF PTR
 	LD	H,(IY+7)		; ... INTO HL
@@ -95,6 +112,7 @@ ACIA_INITUNIT:
 	LD	H,(HL)			; ...
 	LD	L,A			; ...
 	CALL	HB_ADDIM1		; ADD TO IM1 CALL LIST
+#ENDIF
 
 	; SET DEFAULT CONFIG
 	LD	DE,-1			; LEAVE CONFIG ALONE
@@ -117,7 +135,7 @@ ACIA_INIT1:
 	PUSH	HL			; COPY CFG DATA PTR
 	POP	IY			; ... TO IY
 	
-	LD	A,(IY + 1)		; GET ACIA TYPE
+	LD	A,(IY+1)		; GET ACIA TYPE
 	OR	A			; SET FLAGS
 	CALL	NZ,ACIA_PRTCFG		; PRINT IF NOT ZERO
 	
@@ -130,6 +148,8 @@ ACIA_INIT1:
 ;
 ; INTERRUPT HANDLERS
 ;
+#IF (INTMODE > 0)
+;
 ACIAA_INT:
 	LD	IY,ACIAA_CFG		; POINT TO CONFIG
 ;
@@ -216,6 +236,8 @@ ACIAB_INT1:
 	OR	$FF			; NZ SET TO INDICATE INT HANDLED
 	RET				; AND RETURN
 ;
+#ENDIF
+;
 ; DRIVER FUNCTION TABLE
 ;
 ACIA_FNTBL:
@@ -232,6 +254,19 @@ ACIA_FNTBL:
 ;
 ;
 ;
+#IF (INTMODE == 0)
+;
+ACIA_IN:
+	CALL	ACIA_IST		; CHAR WAITING?
+	JR	Z,ACIA_IN		; LOOP IF NOT
+	LD	C,(IY+3)		; C := ACIA BASE PORT
+	INC	C			; BUMP TO DATA PORT
+	IN	E,(C)			; GET BYTE
+	XOR	A			; SIGNAL SUCCESS
+	RET
+;
+#ELSE
+;
 ACIA_IN:
 	LD	A,(IY+2)		; GET MODULE ID
 	OR	A			; SET FLAGS
@@ -251,7 +286,7 @@ ACIAA_IN:
 	CP	5			; BUFFER LOW THRESHOLD
 	JR	NZ,ACIAA_IN0		; IF NOT, BYPASS SETTING RTS
 	
-	LD	C,(IY + 3)		; C := ACIA CMD PORT
+	LD	C,(IY+3)		; C := ACIA CMD PORT
 	LD	A,ACIA_RTSON		; ASSERT RTS
 	OUT	(C),A			; DO IT
 ACIAA_IN0:
@@ -278,7 +313,7 @@ ACIAB_IN:
 	CP	5			; BUFFER LOW THRESHOLD
 	JR	NZ,ACIAB_IN0		; IF NOT, BYPASS SETTING RTS
 	
-	LD	C,(IY + 3)		; C := ACIA CMD PORT
+	LD	C,(IY+3)		; C := ACIA CMD PORT
 	LD	A,ACIA_RTSON		; ASSERT RTS
 	OUT	(C),A			; DO IT
 ACIAB_IN0:
@@ -295,12 +330,14 @@ ACIAB_IN1:
 	XOR	A			; SIGNAL SUCCESS
 	RET				; AND DONE
 ;
+#ENDIF
+;
 ;
 ;
 ACIA_OUT:
 	CALL	ACIA_OST		; READY FOR CHAR?
 	JR	Z,ACIA_OUT		; LOOP IF NOT
-	LD	C,(IY + 3)		; C := ACIA CMD PORT
+	LD	C,(IY+3)		; C := ACIA CMD PORT
 	INC	C			; BUMP TO DATA PORT
 	OUT	(C),E			; SEND CHAR FROM E
 	XOR	A			; SIGNAL SUCCESS
@@ -308,6 +345,19 @@ ACIA_OUT:
 ;
 ;
 ;
+#IF (INTMODE == 0)
+;
+ACIA_IST:
+	LD	C,(IY+3)		; STATUS PORT
+	IN	A,(C)			; GET STATUS
+	AND	$01			; ISOLATE BIT 0 (RX READY)
+	JP	Z,CIO_IDLE		; NOT READY, RETURN VIA IDLE PROCESSING
+	XOR	A			; ZERO ACCUM
+	INC	A			; ASCCUM := 1 TO SIGNAL 1 CHAR WAITING
+	RET				; DONE
+;
+#ELSE
+;
 ACIA_IST:
 	LD	A,(IY+2)		; GET MODULE ID
 	OR	A			; SET FLAGS
@@ -329,10 +379,12 @@ ACIAB_IST:
 	JP	Z,CIO_IDLE		; NOT READY, RETURN VIA IDLE PROCESSING
 	RET				; AND DONE
 ;
+#ENDIF
+;
 ;
 ;
 ACIA_OST:
-	LD	C,(IY + 3)		; CMD PORT
+	LD	C,(IY+3)		; CMD PORT
 	IN	A,(C)			; GET STATUS
 	AND	$02			; ISOLATE BIT 2 (TX EMPTY)
 	JP	Z,CIO_IDLE		; NOT READY, RETURN VIA IDLE PROCESSING
@@ -346,15 +398,17 @@ ACIA_INITDEV:
 	HB_DI				; AVOID CONFLICTS
 ;
 	; PROGRAM THE ACIA CHIP
-	LD	C,(IY + 3)		; COMMAND PORT
+	LD	C,(IY+3)		; COMMAND PORT
 	LD	A,$FF			; MASTER RESET
 	OUT	(C),A			; DO IT
 	LD	A,ACIA_RTSON		; NORMAL OPERATION
 	OUT	(C),A			; DO IT
+;
+#IF (INTMODE > 0)
 ;
 	; RESET THE RECEIVE BUFFER
-	LD	E,(IY + 6)
-	LD	D,(IY + 7)		; DE := _CNT
+	LD	E,(IY+6)
+	LD	D,(IY+7)		; DE := _CNT
 	XOR	A			; A := 0
 	LD	(DE),A			; _CNT = 0
 	INC	DE			; DE := ADR OF _HD
@@ -371,6 +425,8 @@ ACIA_INITDEV:
 	LD	(HL),E
 	INC	HL
 	LD	(HL),D			; _TL := _BUF
+;
+#ENDIF
 ;
 	HB_EI				; READY FOR INTS AGAIN
 	XOR	A			; SIGNAL SUCCESS
@@ -379,8 +435,8 @@ ACIA_INITDEV:
 ;
 ;
 ACIA_QUERY:
-	LD	E,(IY + 4)		; FIRST CONFIG BYTE TO E
-	LD	D,(IY + 5)		; SECOND CONFIG BYTE TO D
+	LD	E,(IY+4)		; FIRST CONFIG BYTE TO E
+	LD	D,(IY+5)		; SECOND CONFIG BYTE TO D
 	XOR	A			; SIGNAL SUCCESS
 	RET				; DONE
 ;
@@ -408,7 +464,7 @@ ACIA_DETECT:
 ACIA_DETECT1:
 	; ACIA FOUND, RECORD IT
 	;LD	A,C		; BASE PORT ADDRESS TO A
-	;LD	(IY + 3),A	; SAVE ACTIVE BASE PORT
+	;LD	(IY+3),A	; SAVE ACTIVE BASE PORT
 	LD	A,ACIA_ACIA	; RETURN CHIP TYPE
 	RET			; DONE
 ;
@@ -436,12 +492,12 @@ ACIA_PRTCFG:
 	LD	A,(IY)			; DEVICE NUM
 	CALL	PRTDECB			; PRINT DEVICE NUM
 	PRTS(": IO=0x$")		; FORMATTING
-	LD	A,(IY + 3)		; GET BASE PORT
+	LD	A,(IY+3)		; GET BASE PORT
 	CALL	PRTHEXBYTE		; PRINT BASE PORT
 
 	; PRINT THE ACIA TYPE
 	CALL	PC_SPACE		; FORMATTING
-	LD	A,(IY + 1)		; GET ACIA TYPE BYTE
+	LD	A,(IY+1)		; GET ACIA TYPE BYTE
 	RLCA				; MAKE IT A WORD OFFSET
 	LD	HL,ACIA_TYPE_MAP	; POINT HL TO TYPE MAP TABLE
 	CALL	ADDHLA			; HL := ENTRY
@@ -451,13 +507,13 @@ ACIA_PRTCFG:
 	CALL	WRITESTR		; PRINT IT
 ;
 	; ALL DONE IF NO ACIA WAS DETECTED
-	LD	A,(IY + 1)		; GET ACIA TYPE BYTE
+	LD	A,(IY+1)		; GET ACIA TYPE BYTE
 	OR	A			; SET FLAGS
 	RET	Z			; IF ZERO, NOT PRESENT
 ;
 	PRTS(" MODE=$")			; FORMATTING
-	LD	E,(IY + 4)		; LOAD CONFIG
-	LD	D,(IY + 5)		; ... WORD TO DE
+	LD	E,(IY+4)		; LOAD CONFIG
+	LD	D,(IY+5)		; ... WORD TO DE
 	CALL	PS_PRTSC0		; PRINT CONFIG
 ;
 	XOR	A
@@ -476,6 +532,13 @@ ACIA_STR_ACIA	.DB	"ACIA$"
 ;
 ACIA_DEV	.DB	0		; DEVICE NUM USED DURING INIT
 ;
+#IF (INTMODE == 0)
+;
+ACIAA_RCVBUF	.EQU	0
+ACIAB_RCVBUF	.EQU	0
+;
+#ELSE
+;
 ; RECEIVE BUFFERS
 ;
 ACIAA_RCVBUF:
@@ -496,6 +559,8 @@ ACIAB_BUF	.FILL	32,0		; RECEIVE RING BUFFER
 ACIAB_BUFEND	.EQU	$		; END OF BUFFER
 ACIAB_BUFSZ	.EQU	$ - ACIAB_BUF	; SIZE OF RING BUFFER
 ;
+#ENDIF
+;
 ; ACIA PORT TABLE
 ;
 ACIA_CFG:
diff --git a/Source/HBIOS/sio.asm b/Source/HBIOS/sio.asm
index c30ab09f..6d3970e4 100644
--- a/Source/HBIOS/sio.asm
+++ b/Source/HBIOS/sio.asm
@@ -507,7 +507,7 @@ BROK:
 	LD	A,E			; 112233445566d1d0 CC
 	RRA				; CC112233445566d1 d0
 	RRA				; d0CC112233445566 d1
-	RRA 			; d1d0CC1122334455 66
+	RRA 				; d1d0CC1122334455 66
 	LD	D,A	
 	RRA				; 66d1d0CC11223344 55
 	AND	$60			; 0011110000000000 00
@@ -555,6 +555,8 @@ BROK:
 	LD	HL,SIO_INITVALS		; POINT TO INIT VALUES
 	LD	B,SIO_INITLEN		; COUNT OF BYTES TO WRITE
 	OTIR				; WRITE ALL VALUES
+;
+#IF (INTMODE > 0)
 ;
 	; RESET THE RECEIVE BUFFER
 	LD	E,(IY+6)
@@ -575,6 +577,8 @@ BROK:
 	LD	(HL),E
 	INC	HL
 	LD	(HL),D			; _TL := _BUF
+;
+#ENDIF
 ;
 	HB_EI				; READY FOR INTS AGAIN
 	XOR	A			; SIGNAL SUCCESS