diff --git a/Source/HBIOS/Config/RCZ280_nat.asm b/Source/HBIOS/Config/RCZ280_nat.asm
index 9eec800d..bcc119f4 100644
--- a/Source/HBIOS/Config/RCZ280_nat.asm
+++ b/Source/HBIOS/Config/RCZ280_nat.asm
@@ -48,3 +48,5 @@ IDEENABLE	.SET	TRUE		; IDE: ENABLE IDE DISK DRIVER (IDE.ASM)
 PPIDEENABLE	.SET	TRUE		; PPIDE: ENABLE PARALLEL PORT IDE DISK DRIVER (PPIDE.ASM)
 ;
 PRPENABLE	.SET	FALSE		; PRP: ENABLE ECB PROPELLER IO BOARD DRIVER (PRP.ASM)
+;
+Z2UOSCEXT	.SET	TRUE		; Z2U: USE EXTERNAL OSCILLATOR
diff --git a/Source/HBIOS/acia.asm b/Source/HBIOS/acia.asm
index 0746c9cd..25c8f2fb 100644
--- a/Source/HBIOS/acia.asm
+++ b/Source/HBIOS/acia.asm
@@ -393,6 +393,7 @@ ACIA_INITDEVX:
 	LD	D,(IY+5)		; HIGH BYTE	
 ;
 ACIA_INITDEV1:
+	LD	(ACIA_NEWCFG),DE	; SAVE NEW CONFIG
 ;
 #IF (ACIADEBUG)
 	PUSH	DE
@@ -493,6 +494,12 @@ ACIA_INITWS2:
 	RLA				; MOVE BITS TO
 	RLA				; ... PROPER LOCATION
 	OR	C			; COMBINE WITH WORKING VALUE
+;
+	; SAVE CONFIG PERMANENTLY NOW
+	LD	DE,(ACIA_NEWCFG)		; GET NEW CONFIG BACK
+	LD	(IY+4),E		; SAVE LOW WORD
+	LD	(IY+5),D		; SAVE HI WORD
+;
 	JR	ACIA_INITGO
 ;
 ACIA_INITSAFE:
@@ -646,6 +653,7 @@ ACIA_STR_ACIA   .DB     "ACIA$"
 ;
 ACIA_DEV        .DB     0               ; DEVICE NUM USED DURING INIT
 ACIA_CMD	.DB	0		; COMMAND PORT SHADOW REGISTER
+ACIA_NEWCFG	.DW	0		; TEMP STORE FOR NEW CFG
 ;
 #IF (INTMODE != 1)
 ;
diff --git a/Source/HBIOS/cfg_master.asm b/Source/HBIOS/cfg_master.asm
index fd2f474e..8aed93cf 100644
--- a/Source/HBIOS/cfg_master.asm
+++ b/Source/HBIOS/cfg_master.asm
@@ -130,7 +130,8 @@ ASCI0CFG	.EQU	DEFSERCFG	; ASCI 0: SERIAL LINE CONFIG
 ASCI1CFG	.EQU	DEFSERCFG	; ASCI 1: SERIAL LINE CONFIG
 ;
 Z2UENABLE	.EQU	FALSE		; Z2U: ENABLE Z280 UART SERIAL DRIVER (Z2U.ASM)
-Z2UOSC		.EQU	1843200		; Z2U:  OSC FREQUENCY IN MHZ
+Z2UOSC		.EQU	1843200		; Z2U: OSC FREQUENCY IN MHZ
+Z2UOSCEXT	.EQU	TRUE		; Z2U: USE EXTERNAL OSCILLATOR
 Z2U0BASE	.EQU	$10		; Z2U 0: BASE I/O ADDRESS
 Z2U0CFG		.EQU	DEFSERCFG	; Z2U 0: SERIAL LINE CONFIG
 ;
diff --git a/Source/HBIOS/cfg_rcz280.asm b/Source/HBIOS/cfg_rcz280.asm
index 847aa1cc..2dfefba7 100644
--- a/Source/HBIOS/cfg_rcz280.asm
+++ b/Source/HBIOS/cfg_rcz280.asm
@@ -103,7 +103,8 @@ UARTRC		.EQU	TRUE		; UART: AUTO-DETECT RC UART
 ASCIENABLE	.EQU	FALSE		; ASCI: ENABLE Z180 ASCI SERIAL DRIVER (ASCI.ASM)
 ;
 Z2UENABLE	.EQU	FALSE		; Z2U: ENABLE Z280 UART SERIAL DRIVER (Z2U.ASM)
-Z2UOSC		.EQU	1843200		; Z2U:  OSC FREQUENCY IN MHZ
+Z2UOSC		.EQU	1843200		; Z2U: OSC FREQUENCY IN MHZ
+Z2UOSCEXT	.EQU	TRUE		; Z2U: USE EXTERNAL OSCILLATOR
 Z2U0BASE	.EQU	$10		; Z2U 0: BASE I/O ADDRESS
 Z2U0CFG		.EQU	DEFSERCFG	; Z2U 0: SERIAL LINE CONFIG
 ;
diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index b9851839..80d23622 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -1864,7 +1864,7 @@ HB_Z280BUS1:
 #ENDIF
 ;
 	CALL	PRTSTRD
-	.TEXT	", MMU=$"
+	.TEXT	", $"
 	CALL	PRTSTRD
 #IF (MEMMGR == MM_NONE)
 	.TEXT	"NONE$"
@@ -1887,6 +1887,8 @@ HB_Z280BUS1:
 #IF (MEMMGR == MM_ZRC)
 	.TEXT	"ZRC$"
 #ENDIF
+	CALL	PRTSTRD
+	.TEXT	" MMU$"
 ;
 ; DISPLAY MEMORY CONFIG
 ;
diff --git a/Source/HBIOS/z2u.asm b/Source/HBIOS/z2u.asm
index 46eeb5ff..040ab5cd 100644
--- a/Source/HBIOS/z2u.asm
+++ b/Source/HBIOS/z2u.asm
@@ -56,6 +56,7 @@
 ; UNLESS FULL BLOWN INTERRUPT MODE 3 W/ NATIVE MEMORY MANAGEMENT
 ; IS BEING USED.
 ;
+;Z2U_BUFSZ	.EQU	32		; RECEIVE RING BUFFER SIZE
 Z2U_BUFSZ	.EQU	128		; RECEIVE RING BUFFER SIZE
 ;
 Z2U_NONE	.EQU	0		; NOT PRESENT
@@ -190,16 +191,17 @@ Z2U_INTRCV1:
 	JR	Z,Z2U_INTRCV4		; BAIL OUT IF BUFFER FULL, RCV BYTE DISCARDED
 	INC	A			; INCREMENT THE COUNT
 	LD	(HL),A			; AND SAVE IT
-	CP	Z2U_BUFSZ / 2		; BUFFER GETTING FULL?
-	JR	NZ,Z2U_INTRCV2		; IF NOT, BYPASS CLEARING RTS
+	;CP	Z2U_BUFSZ / 2		; BUFFER GETTING FULL?
+	;JR	NZ,Z2U_INTRCV2		; IF NOT, BYPASS CLEARING RTS
 	; THIS IS WHERE WE SHOULD DEASSERT RTS, BUT THE Z2U HAS NONE
 Z2U_INTRCV2:
 	INC	HL			; HL NOW HAS ADR OF HEAD PTR
 	PUSH	HL			; SAVE ADR OF HEAD PTR
-	LD	A,(HL)			; DEREFERENCE HL
-	INC	HL
-	LD	H,(HL)
-	LD	L,A			; HL IS NOW ACTUAL HEAD PTR
+	;LD	A,(HL)			; DEREFERENCE HL
+	;INC	HL
+	;LD	H,(HL)
+	;LD	L,A			; HL IS NOW ACTUAL HEAD PTR
+	.DB	$ED,$26			; LD HL,(HL) ; DEREFERENCE HL, HL IS NOW ACTUAL HEAD PTR
 	LD	(HL),B			; SAVE CHARACTER RECEIVED IN BUFFER AT HEAD
 	INC	HL			; BUMP HEAD POINTER
 	POP	DE			; RECOVER ADR OF HEAD PTR
@@ -215,9 +217,10 @@ Z2U_INTRCV2:
 	INC	HL			; ... SO HL NOW HAS ADR OF ACTUAL BUFFER START
 Z2U_INTRCV3:
 	EX	DE,HL			; DE := HEAD PTR VAL, HL := ADR OF HEAD PTR
-	LD	(HL),E			; SAVE UPDATED HEAD PTR
-	INC	HL
-	LD	(HL),D
+	;LD	(HL),E			; SAVE UPDATED HEAD PTR
+	;INC	HL
+	;LD	(HL),D
+	.DB	$ED,$1E			;LD (HL),DE ; SAVE UPDATED HEAD PTR
 
 	; CHECK FOR MORE PENDING...
 	IN	A,(Z280_UARTRCTL)	; GET STATUS
@@ -416,11 +419,23 @@ Z2U_INITDEV:
 	RET				; DONE
 ;
 Z2U_INITSAFE:
-	LD	E,%11000010		; 8N0, DIV 16, NO C/T
-	JR	Z2U_INITDEV2		; YES, DO IT
+	LD	A,%11000010		; 8N0, DIV 16, NO C/T
+	LD	(Z2U_CFGREG),A		; SAVE IT
+	JR	Z2U_INITDEV8		; DO IT
 ;
 Z2U_INITDEVX:
-;
+	; TEST FOR -1 WHICH MEANS USE CURRENT CONFIG (JUST REINIT)
+	LD	A,D			; TEST DE FOR
+	AND	E			; ... VALUE OF -1
+	INC	A			; ... SO Z SET IF -1
+	JR	NZ,Z2U_INITDEV1		; IF DE == -1, REINIT CURRENT CONFIG
+;
+	; LOAD EXISTING CONFIG TO REINIT
+	LD	E,(IY+4)		; LOW BYTE
+	LD	D,(IY+5)		; HIGH BYTE	
+;
+Z2U_INITDEV1:
+	LD	(Z2U_NEWCFG),DE		; SAVE NEW CONFIG
 	LD	A,D			; HIWORD OF CONFIG
 	AND	$1F			; ISOLATE BAUD RATE
 	PUSH	AF
@@ -430,42 +445,99 @@ Z2U_INITDEVX:
 	LD	C,75			; BAUD RATE ENCODE CONSTANT
 	CALL	ENCODE			; C = ENCODED OSC
 	POP	DE			; D = UART OSC
-	JR	NZ,Z2U_INITFAIL		; HANDLE ENCODE FAILURE
+	JP	NZ,Z2U_INITFAIL		; HANDLE ENCODE FAILURE
 	LD	A,C			; TO A
 	SUB	D			; DIV W/ SUB OF SQUARES
+	; REG A NOW HAS ENCODED BAUD RATE DIVISOR
+;
+	PUSH	AF			; SAVE IT
+	AND	$0F			; ISOLATE 2'S POWER
 ;
+	; Z280 UART CAN USE 16, 32, OR 64 AS BAUD RATE DIVISOR
+	; SET E TO IMPLEMENT WHAT WE CAN
+	LD	E,%11000000		; 8N0, DIV 1, NO C/T
+	;JR	Z2U_INITDEV2		; *DEBUG*
+	CP	4			; DIV 16 POSSIBLE?
+	JR	C,Z2U_INITDEV2		; IF NOT, SKIP AHEAD
 	LD	E,%11000010		; 8N0, DIV 16, NO C/T
-	CP	4			; DIV 16?
-	JR	Z,Z2U_INITDEV2		; YES, DO IT
+	SUB	4			; REFLECT IN TGT DIVISOR
+	CP	1			; DIV 32 POSSIBLE?
+	JR	C,Z2U_INITDEV2		; IF NOT, SKIP AHEAD
 	LD	E,%11000100		; 8N0, DIV 32, NO C/T
-	CP	5			; DIV 32?
-	JR	Z,Z2U_INITDEV2		; YES, DO IT
+	DEC	A			; REFLECT IN TGT DIVISOR
+	CP	1			; DIV 64 POSSIBLE?
+	JR	C,Z2U_INITDEV2		; IF NOT, SKIP AHEAD
 	LD	E,%11000110		; 8N0, DIV 64, NO C/T
-	CP	6			; DIV 64?
-	JR	Z,Z2U_INITDEV2		; YES, DO IT
-;
-Z2U_INITFAIL:
-	OR	$FF			; SIGNAL ERROR
-	RET				; AND DONE
+	DEC	A
 ;
 Z2U_INITDEV2:
+	LD	D,A			; 2'S POWER TO D
+	POP	AF			; RECOVER ORIGINAL VALUE
+	AND	$F0			; MASK OFF ORIG 2'S POWER
+	OR	D			; COMBINE
+	;CALL	PRTHEXBYTE		; *DEBUG*
+	PUSH	AF			; RESAVE IT
+	LD	A,E			; GET Z280 UART CONFIG REG VAL
+	LD	(Z2U_CFGREG),A		; SAVE CONFIG REG VALUE FOR LATER
+	POP	AF			; RECOVER REMAINING ENCODED DIVISOR
+	LD	L,A			; INTO L
+	LD	H,0			; H MUST BE ZERO
+	LD	DE,1			; RATIO, SO NO CONSTANT
+	CALL	DECODE			; DECODE INTO DE:HL
+	;LD	HL,626			; *DEBUG*
+	JR	NZ,Z2U_INITFAIL		; HANDLE FAILURE
+	;CALL	PC_SPACE		; *DEBUG* 
+	;CALL	PRTHEXWORDHL            ; *DEBUG*
+;
+	; SAVE CONFIG PERMANENTLY NOW
+	LD	DE,(Z2U_NEWCFG)		; GET NEW CONFIG BACK
+	LD	(IY+4),E		; SAVE LOW WORD
+	LD	(IY+5),D		; SAVE HI WORD
+;
+Z2U_INITDEV8:
 	; START BY SELECTING I/O PAGE $FE
+	PUSH	HL			; SAVE HL
 	LD	L,$FE			; Z280 UART REGISTERS AT I/O PAGE $FE
 	LD	C,Z280_IOPR		; REG C POINTS TO I/O PAGE REGISTER
 	.DB	$ED,$6E			; LDCTL	(C),HL
+	POP	HL			; RESTORE HL
+;
+	DEC	HL			; ADJUST FOR T/C
+	LD	A,H			; TEST FOR
+	OR	L			; ... ZERO
+	JR	Z,Z2U_INITDEV9		; IF ZERO, SKIP C/T
 ;
-	; SETUP
-	;LD	A,%11000010		; 8N0, DIV 16, NO C/T
-	LD	A,E			; CONFIG VALUE
+	; PROGRAM C/T 1
+#IF	Z2UOSCEXT
+	LD	A,%10001100		; CONFIG: C, RE, COUNTER
+#ELSE
+	LD	A,%10001000		; CONFIG: C, RE, COUNTER
+#ENDIF
+	OUT	(Z280_CT1_CFG),A	; SET C/T 1
+	LD	C,Z280_CT1_TC		; SET C/T 1 FROM HL
+	.DB	$ED,$BF			; OUTW (C),HL
+	LD	C,Z280_CT1_CT		; SET C/T 1 FROM HL
+	.DB	$ED,$BF			; OUTW (C),HL
+	LD	A,%11100000		; CMD: EN, GT, TG
+	OUT	(Z280_CT1_CMDST),A	; SET C/T 1
+;
+	; MODIFY CFG REG VALUE TO USE C/T
+	LD	A,(Z2U_CFGREG)		; CONFIG VALUE
+	SET	3,A			; SET C/T USAGE BIT
+	LD	(Z2U_CFGREG),A		; SAVE IT
+;
+Z2U_INITDEV9:
+	; PROGRAM THE UART
+	LD	A,(Z2U_CFGREG)		; CONFIG VALUE
 	OUT	(Z280_UARTCFG),A	; SET CONFIG REGISTER
 	LD	A,%10000000		; ENABLE, NO INTS, 1 STOP BITS
-	OUT	(Z280_UARTXCTL),A	; SET CONFIG REGISTER
+	OUT	(Z280_UARTXCTL),A	; SET XMIT CTL REGISTER
 #IF (INTMODE == 3)
-	LD	A,%11000000		; ENABLE W/ INTS
+	LD	A,%11000000		; ENABLE W/ RCV INTS
 #ELSE
-	LD	A,%10000000		; ENABLE, NO INTS
+	LD	A,%10000000		; ENABLE, NO RCV INTS
 #ENDIF
-	OUT	(Z280_UARTRCTL),A	; SET CONFIG REGISTER
+	OUT	(Z280_UARTRCTL),A	; SET RCV CTL REGISTER
 ;	
 	; RESTORE I/O PAGE TO $00
 	LD	L,$00			; NORMAL I/O REG IS $00
@@ -496,9 +568,14 @@ Z2U_INITDEV2:
 ;
 #ENDIF
 ;
+	; RETURN SUCCESS
 	XOR	A			; SIGNAL SUCCESS
 	RET				; DONE
 ;
+Z2U_INITFAIL:
+	OR	$FF			; SIGNAL ERROR
+	RET				; AND DONE
+;
 ;
 ;
 Z2U_QUERY:
@@ -552,7 +629,9 @@ Z2U_PRTCFG:
 ;
 ; WORKING VARIABLES
 ;
-Z2U_DEV	.DB	0			; DEVICE NUM USED DURING INIT
+Z2U_DEV		.DB	0		; DEVICE NUM USED DURING INIT
+Z2U_CFGREG	.DB	0		; VALUE TO PROGRAM CFG REG
+Z2U_NEWCFG	.DW	0		; TEMP STORE FOR NEW CFG
 ;
 #IF (INTMODE < 3)
 ;
diff --git a/Source/ver.inc b/Source/ver.inc
index 0a509e88..39594378 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.40"
+#DEFINE BIOSVER	"3.1.1-pre.41"
diff --git a/Source/ver.lib b/Source/ver.lib
index 4ceb188d..e8892882 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.40"
+	db	"3.1.1-pre.41"
 	endm