diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index d522bab0..aa3a4ccf 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -66,11 +66,8 @@
 ;
 ; TODO
 ; - Add remaining service routine stubs for IM3 (NMI, etc.)
-; - Review PEEK/POKE code for Z280
 ; - Review bank selection code (selectable user/sys bank?)
-; - Check app boot under Z280
-; - Relocate Z280_PRIVINST
-;
+; - Fix app boot under Z280
 ;
 ; INCLUDE GENERIC STUFF
 ;
@@ -323,26 +320,17 @@ HBX_INVOKE:
 
 	LD	A,(HB_CURBNK)		; GET CURRENT BANK
 	LD	(HB_INVBNK),A		; SAVE INVOCATION BANK
-
+	
 	LD	A,BID_BIOS		; HBIOS BANK
 	LD	(HB_CURBNK),A		; SET AS CURRENT BANK
 
 	.DB	$ED,$71			; SC
 	.DW	HB_DISPATCH		; SC PARAMETER
-
-	PUSH	AF			; SAVE AF (FUNCTION RETURN)
-	PUSH	HL			; SAVE HL
-	LD	A,(HB_INVBNK)		; LOAD ORIGINAL BANK
-	LD	HL,HB_CURBNK
-	CP	(HL)			; BANK CHANGE?
-	POP	HL			; RESTORE HL
-	JR	Z,HBX_INVOKE1		; SKIP IF NO CHANGE
-	CALL	HBX_BNKSEL		; DO THE CHANGE
-	JR	HBX_INVOKE2		; AND CONTINUE
-HBX_INVOKE1:
-	LD	(HB_CURBNK),A		; JUST UPDATE CURBNK FIELD
-HBX_INVOKE2:
-	POP	AF			; RESTORE AF
+	
+	PUSH	AF
+	LD	A,(HB_INVBNK)
+	LD	(HB_CURBNK),A
+	POP	AF
 
 #ELSE
 
@@ -417,6 +405,7 @@ HBX_ROM:
 	OUT	(MPCL_ROM),A		; SET ROM PAGE SELECTOR
 	RET				; DONE
 #ENDIF
+;
 #IF (MEMMGR == MM_Z2)
 	BIT	7,A			; BIT 7 SET REQUESTS RAM PAGE
 	JR	Z,HBX_ROM		; NOT SET, SELECT ROM PAGE
@@ -433,6 +422,7 @@ HBX_ROM:
 #ENDIF
 	RET				; DONE
 #ENDIF
+;
 #IF (MEMMGR == MM_N8)
 	BIT	7,A			; TEST BIT 7 FOR RAM VS. ROM
 	JR	Z,HBX_ROM		; IF NOT SET, SELECT ROM PAGE
@@ -454,8 +444,8 @@ HBX_ROM:
 	LD	A,N8_DEFACR		; SELECT ROM  BY CLEARING BIT 7
 	OUT0	(N8_ACR),A		; ... IN N8 ACR REGISTER
 	RET				; DONE
-;
 #ENDIF
+;
 #IF (MEMMGR == MM_Z180)
 	RLCA				; RAM FLAG TO CARRY FLAG AND BIT 0
 	JR	NC,HBX_BNKSEL1		; IF NC, WANT ROM PAGE, SKIP AHEAD
@@ -466,19 +456,13 @@ HBX_BNKSEL1:
 	OUT0	(Z180_BBR),A		; WRITE TO BANK BASE
 	RET				; DONE
 #ENDIF
+;
 #IF (MEMMGR == MM_Z280)
 	.DB	$ED,$71			; SC
 	.DW	Z280_BNKSEL		; SC PARAMETER
 	RET
-;
-Z280_SYSCALL:
-	EX	(SP),HL
-	LD	(Z280_SCADR),HL
-	POP	HL
-Z280_SCADR	.EQU	$ + 1
-	CALL	$FFFF
-	.DB	$ED,$55			; RETIL
 #ENDIF
+;
 #IF (MEMMGR == MM_ZRC)
 	BIT	7,A			; BIT 7 SET REQUESTS RAM PAGE
 	JR	Z,HBX_ROM		; NOT SET, SELECT ROM PAGE
@@ -509,122 +493,20 @@ HBX_BNKCPY:
 	.DB	$ED,$71			; SC
 	.DW	Z280_BNKCPY		; SC PARAMETER
 	RET
-	
-;
-; Z280 BANK SELECTION (CALLED FROM PROXY)
-;
-#IF (MEMMGR == MM_Z280) & FALSE
-;
-Z280_BNKCPY:
-	; Z280 MEMORY TO MEMORY DMA
-	; USE FLOW THROUGH MODE DMA
-	; SINGLE BYTE TRANSFER
-	; TRANSACTION DESCRIPTION REGISTER (TDR)
-	; %0000 0000 0000 0000
-	; - AUTO INCREMENT MEMORY
-	; - FLOWTHROUGH OPERATION
-	; - SINGLE TRANSACTION
-	; - 1 BYTE XFER SIZE
-
+#ELSE
+  #IF (CPUFAM == CPU_Z280)
 	PUSH	HL
-	PUSH	DE
 	PUSH	BC
-
-	PUSH	BC			; SAVE COUNT
-	PUSH	HL			; SAVE SOURCE ADDRESS
-	
-	; SELECT I/O PAGE $FF
-	LD	L,$FF			; I/O PAGE $FF
-	LD	C,Z280_IOPR		; I/O PAGE REGISTER
-	.DB	$ED,$6E			; LDCTL (C),HL
-	
-	LD	C,Z280_DMA0_DSTL	; START WITH DEST REG LO
-
-	LD	A,(HB_DSTBNK)		; DEST BANK TO ACCUM
-	CALL	Z2DMAADR		; SETUP DEST ADR REGS
-	
-	POP	DE			; SRC ADR TO DE
-	LD	A,(HB_SRCBNK)		; DEST BANK TO ACCUM
-	CALL	Z2DMAADR		; SETUP SOURCE ADR REGS
-
-	POP	HL			; COUNT TO HL
-	.DB	$ED,$BF			; OUTW (C),HL
-	INC	C			; BUMP TO TDR
-
-	LD	HL,$8000		; ENABLE DMA0 TO RUN!
-	.DB	$ED,$BF			; OUTW (C),HL
-
-	; WAIT FOR XFER TO COMPLETE
-Z2DMALOOP:
-	.DB	$ED,$B7			; INW HL,(C)
-	BIT	7,H			; CHECK EN BIT OF TDR
-	JR	NZ,Z2DMALOOP		; LOOP WHILE ACTIVE
-
-	; RETURN TO I/O PAGE $00
-	XOR	A			; I/O PAGE ZERO
-	LD	C,Z280_IOPR		; I/O PAGE REGISTER
-	.DB	$ED,$6E			; LDCTL (C),HL
-
-	; SETUP RETURN VALUES
-	POP	BC			; RECOVER ORIGINAL BC
-	POP	DE			; RECOVER ORIGINAL DE
-	POP	HL			; RECOVER ORIGINAL HL
-	ADD	HL,BC			; INCREMENT SRC ADR BY COUNT
-	EX	DE,HL			; SWAP
-	ADD	HL,BC			; INCREMENT DST ADR BY COUNT
-	EX	DE,HL			; SWAP BACK
-	LD	BC,0			; COUNT IS NOW ZERO
-
-	RET
-
-Z2DMAADR:
-	; SET ADDRESS REGISTERS, BANK IN A, ADDRESS IN DE
-	; C POINTS TO FIRST DMA ADR PORT TO SET
-	BIT	7,D			; HIGH RAM?
-	JR	Z,Z2DMAADR0		; NO, SKIP
-	LD	A,$8F			; SUBSTITUTE COMMON RAM BANK ID
-
-Z2DMAADR0:
-	BIT	7,A			; RAM?
-	JR	Z,Z2DMAADR1		; NO, SKIP
-	RES	7,A			; CLEAR RAM BIT
-	SET	4,A			; SET BIT FOR 512K OFFSET
-
-Z2DMAADR1:
-	; ADR HI FROM A:DE
-	LD	L,D			; L=XAAA AAAA
-	LD	H,A			; H=BBBB BBBB
-	SLA	L			; L=AAAA AAA0
-	SRL	H			; H=0BBB BBBB B
-	RR	L			; L=BAAA AAAA
-	LD	A,$0F			; A=0000 1111
-	OR	L			; A=BAAA 1111
-	LD	L,A			; L=BAAA 1111
-	PUSH	HL			; SAVE IT FOR NOW
-
-	; ADR LO FROM DE:
-	LD	L,E			; L= AAAA AAAA
-	LD	A,$F0			; A= 1111 0000
-	OR	D			; A= 1111 AAAA
-	LD	H,A			; HL=1111 AAAA AAAA AAAA
-
-	; SET ADR LO REG
-	.DB	$ED,$BF			; OUTW (C),HL
-	INC	C			; BUMP TO ADR HI REG
-
-	; SET ADR HI REG
-	POP	HL			; RECOVER THE HI VAL
-
-	.DB	$ED,$BF			; OUTW (C),HL
-	INC	C			; BUMP TO NEXT REG
-	
-	RET
-#ENDIF
-
-#ELSE
+	LD	C,Z280_MSR
+	.DB	$ED,$66			; LDCTL HL,(C)
+	POP	BC
+	EX	(SP),HL
+	DI
+  #ELSE
 	LD	A,I
 	DI
 	PUSH	AF
+  #ENDIF
 	LD	(HBX_BC_SP),SP		; PUT STACK
 	LD	SP,HBX_TMPSTK		; ... IN HI MEM
 
@@ -654,9 +536,18 @@ HBX_BC_LAST:
 
 	LD	SP,$FFFF		; RESTORE STACK
 HBX_BC_SP	.EQU	$ - 2		; ... TO ORIGINAL VALUE
+  #IF (CPUFAM == CPU_Z280)
+	EX	(SP),HL			; SAVE HL, RECOVER MSR
+	PUSH	BC			; SAVE BC
+	LD	C,Z280_MSR
+	.DB	$ED,$6E			; LDCTL (C),HL
+	POP	BC			; RECOVER BC
+	POP	HL			; RECOVER HL
+  #ELSE
 	POP	AF
 	JP	PO,$+4
 	EI
+  #ENDIF
 	RET
 ;
 HBX_BC_ITER:
@@ -738,11 +629,28 @@ HBX_POKE:
 ;
 HBX_PPRET:
 	POP	AF
+#IF (MEMMGR == MM_Z280)
+	LD	A,(HB_INVBNK)		; SPECIAL CASE FOR Z280 MEM MGR
+#ENDIF
 	CALL	HBX_BNKSEL
 	LD	SP,0			; RESTORE ORIGINAL STACK FRAME
 HBX_PPSP	.EQU	$ - 2
 	RET
 ;
+; SYSCALL VECTOR ENTRY POINT.  TAKES STACK PARAMETER AS A BRANCH
+; ADDRESS AND CALLS IT.  ALLOWS ANY USER MODE CODE TO CALL INTO AN
+; ARBITRARY LOCATION OF SYSTEM MODE CODE.
+;
+#IF (MEMMGR == MM_Z280)
+Z280_SYSCALL:
+	EX	(SP),HL
+	LD	(Z280_SYSCALL_GO+1),HL
+	POP	HL
+Z280_SYSCALL_GO:
+	CALL	$FFFF			; PARM SET ABOVE
+	.DB	$ED,$55			; RETIL
+#ENDIF
+;
 ; PRIVATE STACK AT END OF HBIOS CODE
 ; OCCUPIES SPACE BEFORE IVT
 ;
@@ -1094,7 +1002,7 @@ HB_START:
 ;
 	; CONFIGURE Z280 INT/TRAP VECTOR TABLE POINTER REGISTER
 	LD	C,Z280_VPR
-	LD	HL,$0010		; TOP 16 BITS OF PHYSICAL ADR OF IVT
+	LD	HL,Z280_IVT >> 8	; TOP 16 BITS OF PHYSICAL ADR OF IVT
 	.DB	$ED,$6E			; LDCTL	(C),HL
 ;
 	JP	Z280_INITZ		; JUMP TO CODE CONTINUATION
@@ -1119,74 +1027,6 @@ Z280_PDRTBL:
 	.DW	($0FE << 4) | $A
 	.DW	($0FF << 4) | $A
 ;
-Z280_PRIVINST:
-	EX	(SP),HL			; GET MSR, SAVE HL
-	LD	(HB_MSRSAV),HL		; SAVE IT
-	POP	HL			; RECOVER HL, POP STACK
-	EX	(SP),HL			; GET ADR, SAVE HL
-	
-	PUSH	AF
-	PUSH	BC
-	PUSH	DE
-	
-	.DB	$ED,$96			; LDUP	A,(HL)
-	INC	HL			; BUMP PAST PRIV INST
-	
-	;CALL	PC_LBKT
-	;CALL	PRTHEXBYTE
-	;CALL	PC_RBKT
-	
-	; HANDLE DI
-	CP	$F3			; DI?
-	JR	NZ,Z280_PRIVINST2
-	DI				; DO THE DI
-	JR	Z280_PRIVINSTX
-
-Z280_PRIVINST2:
-	; HANDLE EI
-	CP	$FB			; EI?
-	JR	NZ,Z280_PRIVINST_HALT
-	EI				; DO THE EI
-	JR	Z280_PRIVINSTX
-
-Z280_PRIVINST_HALT:
-	; SOMETHING ELSE, DIAGNOSE & HALT SYSTEM
-	
-	PUSH	HL
-	CALL	PC_LBKT
-	CALL	PRTHEXBYTE
-	.DB	$ED,$96			; LDUP	A,(HL)
-	CALL	PRTHEXBYTE
-	INC	HL
-	.DB	$ED,$96			; LDUP	A,(HL)
-	CALL	PRTHEXBYTE
-	CALL	PC_RBKT
-	POP	HL
-
-	CALL	NEWLINE
-	LD	DE,Z280_PRIVSTR
-	CALL	WRITESTR
-	DEC	HL
-	CALL	PRTHEXWORDHL
-	
-	DI
-	HALT
-
-Z280_PRIVINSTX:	
-	POP	DE
-	POP	BC
-	POP	AF
-	
-	EX	(SP),HL			; RECOVER HL, ADR TO STK
-	PUSH	HL			; SAVE HL
-	LD	HL,(HB_MSRSAV)		; GET SAVED MSR
-	EX	(SP),HL			; MSR TO STK, RECOVER HL
-	.DB	$ED,$55			; RETIL
-;
-HB_MSRSAV	.DW	0
-;
-Z280_PRIVSTR	.TEXT	"\n\n*** Privileged Instruction @$"
-;
 Z280_INITZ:
 ;
   #ENDIF 
@@ -1366,6 +1206,13 @@ HB_START1:				; BNKCALL ARRIVES HERE, BUT NOW RUNNING IN RAM BANK
 	LD	A,TRUE			; ACCUM := TRUE
 	LD	(HB_RAMFLAG),A		; SET RAMFLAG
 ;
+#IF (MEMMGR == MM_Z280)
+	; NOW POINT TO RAM COPY OF Z280 INT/TRAP TABLE
+	LD	C,Z280_VPR
+	LD	HL,$0E80+(Z280_IVT >> 8)	; TOP 16 BITS OF PHYSICAL ADR OF IVT
+	.DB	$ED,$6E			; LDCTL	(C),HL
+#ENDIF
+;
 ; IF APPBOOT, WE NEED TO FIX UP A FEW THINGS IN PAGE ZERO
 ;
 #IFDEF APPBOOT
@@ -1602,7 +1449,7 @@ HB_CPU2:
 	LD	C,Z280_BTIR		; BUS TIMING AND INIT REG
 	.DB	$ED,$66			; LDCTL	HL,(C)
 	LD	A,L			; PUT IN A
-	AND	%11110011		; CLEAR DC AND I/O FIELDS
+	AND	%11110011		; CLEAR LOW MEM WAIT STATES
 	OR	Z280_MEMWAIT << 2	; SET LOW MEM WAIT STATES
 	LD	L,A			; BACK TO L
 	.DB	$ED,$6E			; LDCTL	(C),HL
@@ -1816,158 +1663,6 @@ NXTMIO:	LD	A,(HL)
 	CALL	PRTSTRD
 	.TEXT	"HBIOS MUTEX ENABLED$"
 #ENDIF
-
-
-
-;;;
-;;; TEST DMA *****************************************************************************************
-;;;
-;;TSTDMA:
-;;
-;;	CALL	NEWLINE
-;;	LD	DE,TSTDST
-;;	LD	A,$10
-;;	CALL	PRTHEXBUF
-;;
-;;	; USE FLOW THROUGH MODE DMA
-;;	; SINGLE BYTE TRANSFER
-;;	; TRANSACTION DESCRIPTION REGISTER (TDR)
-;;	; %0000 0000 0000 0000
-;;	; - AUTO INCREMENT MEMORY
-;;	; - FLOWTHROUGH OPERATION
-;;	; - SINGLE TRANSACTION
-;;	; - 1 BYTE XFER SIZE
-;;	
-;;	LD	A,$8D
-;;	LD	(HB_DSTBNK),A
-;;	LD	(HB_SRCBNK),A
-;;	LD	HL,TSTSRC
-;;	LD	DE,TSTDST
-;;	LD	BC,$0010
-;;
-;;	
-;;	
-;;	CALL	HBX_BNKCPY
-;;	JP	ENDTST
-;;
-;;	PUSH	BC			; SAVE COUNT
-;;	PUSH	HL			; SAVE SOURCE ADDRESS
-;;	
-;;	; SELECT I/O PAGE $FF
-;;	LD	L,$FF			; I/O PAGE $FF
-;;	LD	C,Z280_IOPR		; I/O PAGE REGISTER
-;;	.DB	$ED,$6E			; LDCTL (C),HL
-;;	
-;;	LD	C,Z280_DMA0_DSTL	; START WITH DEST REG LO
-;;
-;;	LD	A,(HB_DSTBNK)		; DEST BANK TO ACCUM
-;;	CALL	SETADR			; SETUP DEST ADR
-;;	
-;;	LD	(DSTHI),IY
-;;	LD	(DSTLO),IX
-;;	
-;;	POP	DE			; SRC ADR TO DE
-;;	LD	A,(HB_SRCBNK)		; DEST BANK TO ACCUM
-;;	CALL	SETADR
-;;
-;;	LD	(SRCHI),IY
-;;	LD	(SRCLO),IX
-;;	
-;;	POP	HL			; COUNT TO HL
-;;	.DB	$ED,$BF			; OUTW (C),HL
-;;	INC	C			; BUMP TO TDR
-;;
-;;	LD	HL,$8000		; ENABLE DMA0 TO RUN!
-;;	.DB	$ED,$BF			; OUTW (C),HL
-;;
-;;	; WAIT FOR XFER TO COMPLETE
-;;DMALOOP:
-;;	.DB	$ED,$B7			; INW HL,(C)
-;;	BIT	7,H			; CHECK EN BIT OF TDR
-;;	JR	NZ,DMALOOP		; LOOP WHILE ACTIVE
-;;
-;;	; RETURN TO I/O PAGE $00
-;;	XOR	A			; I/O PAGE ZERO
-;;	LD	C,Z280_IOPR		; I/O PAGE REGISTER
-;;	.DB	$ED,$6E			; LDCTL (C),HL
-;;
-;;	JR	ENDTST
-;;
-;;SETADR:
-;;
-;;	; SET ADDRESS REGISTERS, BANK IN A, ADDRESS IN DE
-;;	; C POINTS TO FIRST DMA ADR PORT TO SET
-;;
-;;	BIT	7,A			; RAM?
-;;	JR	Z,CONT			; NO, SKIP
-;;	RES	7,A			; CLEAR RAM BIT
-;;	SET	4,A			; SET BIT FOR 512K OFFSET
-;;
-;;CONT:
-;;	; ADR HI FROM A:DE
-;;	LD	L,D			; L=XAAA AAAA
-;;	LD	H,A			; H=BBBB BBBB
-;;	SLA	L			; L=AAAA AAA0
-;;	SRL	H			; H=0BBB BBBB B
-;;	RR	L			; L=BAAA AAAA
-;;	LD	A,$0F			; A=0000 1111
-;;	OR	L			; A=BAAA 1111
-;;	LD	L,A			; L=BAAA 1111
-;;	PUSH	HL			; SAVE IT FOR NOW
-;;
-;;	; ADR LO FROM DE:
-;;	LD	L,E			; L= AAAA AAAA
-;;	LD	A,$F0			; A= 1111 0000
-;;	OR	D			; A= 1111 AAAA
-;;	LD	H,A			; HL=1111 AAAA AAAA AAAA
-;;	
-;;	PUSH	HL
-;;	POP	IX
-;;
-;;	; SET ADR LO REG
-;;	.DB	$ED,$BF			; OUTW (C),HL
-;;	INC	C			; BUMP TO ADR HI REG
-;;
-;;	; SET ADR HI REG
-;;	POP	HL			; RECOVER THE HI VAL
-;;
-;;	PUSH	HL
-;;	POP	IY
-;;
-;;	.DB	$ED,$BF			; OUTW (C),HL
-;;	INC	C			; BUMP TO NEXT REG
-;;	
-;;	RET
-;;
-;;
-;;TSTSRC	.DB	$00, $11, $22, $33, $44, $55, $66, $77
-;;	.DB	$88, $99, $AA, $BB, $CC, $DD, $EE, $FF
-;;
-;;TSTDST	.FILL	16,$12
-;;
-;;SRCHI	.DW	0
-;;SRCLO	.DW	0
-;;DSTHI	.DW	0
-;;DSTLO	.DW	0
-;;
-;;ENDTST:
-;;	CALL	NEWLINE
-;;	LD	BC,(SRCHI)
-;;	CALL	PRTHEXWORD
-;;	CALL	PC_SPACE
-;;	LD	BC,(SRCLO)
-;;	CALL	PRTHEXWORD
-;;	CALL	NEWLINE
-;;	LD	BC,(DSTHI)
-;;	CALL	PRTHEXWORD
-;;	CALL	PC_SPACE
-;;	LD	BC,(DSTLO)
-;;	CALL	PRTHEXWORD
-;;
-;;	CALL	NEWLINE
-;;	LD	DE,TSTDST
-;;	LD	A,$10
-;;	CALL	PRTHEXBUF
 ;
 	DIAG(%11111111)
 ;
@@ -2209,16 +1904,26 @@ INITSYS4:
 	; LEAVE SYSTEM MODE STACK POINTING TO AN OK PLACE
 	LD	SP,HB_STACK		; NOW USE REAL SYSTEM STACK LOC
 	
-	HB_DI
+	HB_DI				; NOT SURE THIS IS NEEDED
 
 	; FIXUP BNKSEL TO WORK ON USER MODE PDRS
 	XOR	A
 	LD	(W_MMU0+1),A
 	LD	(W_MMU1+1),A
 	
-	; FIXUP SYSCALL TO KEEP INTERRUPTS ENABLED
-	LD	HL,$007F
-	LD	(Z280_IVT + $50),HL
+	;CALL	NEWLINE
+	;LD	DE,$1050
+	;LD	A,4
+	;CALL	PRTHEXBUF
+
+	;; FIXUP SYSCALL TO KEEP INTERRUPTS ENABLED
+	;LD	HL,$007F
+	;LD	(Z280_IVT + $50),HL
+	
+	;CALL	NEWLINE
+	;LD	DE,$1050
+	;LD	A,4
+	;CALL	PRTHEXBUF
 
 	; MAKE USER MODE BANK CORRECT
 	LD	A,(HB_CURBNK)		; GET CURRENT BANK
@@ -2228,7 +1933,7 @@ INITSYS4:
 	LD	HL,HBX_LOC
 	.DB	$ED,$8F			; LDCTL	USP,HL
 
-	HB_EI
+	HB_EI				; NOT SURE THIS IS NEEDED
 
 	; SWITCH TO USER MODE NOW
 	LD	C,Z280_MSR
@@ -2476,6 +2181,10 @@ IDLE:
 HB_DISPATCH:
 ;
 #IF (MEMMGR == MM_Z280)
+	; FOR Z280 MEMMGR, WE DISPATCH VIA THE Z280 SYSCALL.
+	; THE SYSCALL MECHANISM WILL CLEAR INTERRUPTS.  IN
+	; GENERAL, INTERRUPTS ARE OK DURING API PROCESSING,
+	; SO ENABLE THEM HERE.
 	HB_EI
 #ENDIF
 ;
@@ -3093,6 +2802,20 @@ SYS_VER:
 ;   CALLER MUST EXTABLISH UPPER MEMORY STACK BEFORE INVOKING THIS FUNCTION!
 ;
 SYS_SETBNK:
+#IF (MEMMGR == MM_Z280)
+	; FOR Z280 MEMMGR, WE ARE IN SYSTEM MODE HERE, SO WE CAN UPDATE
+	; THE USER MODE BANK WITHOUT IMPACTING THE RUNNING CODE.  IT
+	; TAKE EFFECT UPON RETURN TO USER MODE.
+	LD	A,(HB_INVBNK)		; GET PREVIOUS BANK
+	PUSH	AF			; SAVE IT
+	LD	A,C			; NEW BANK TO A
+	LD	(HB_INVBNK),A		; UPDATE INVBNK
+	CALL	Z280_BNKSEL		; DO IT
+	POP	AF			; RECOVER PREV BANK
+	LD	C,A			; PREVIOUS BANK TO C
+	XOR	A			; SIGNAL SUCCESS
+	RET				; DONE
+#ELSE
 	PUSH	HL			; SAVE INCOMING HL
 	LD	HL,HB_INVBNK		; POINT TO HBIOS INVOKE BANK ID ADDRESS
 	LD	A,(HL)			; GET EXISTING BANK ID TO A
@@ -3101,6 +2824,7 @@ SYS_SETBNK:
 	POP	HL			; RESTORE ORIGINAL HL
 	XOR	A			; SIGNAL SUCCESS
 	RET				; DONE
+#ENDIF
 ;
 ; GET ACTIVE MEMORY BANK
 ;
@@ -3749,6 +3473,98 @@ HB_BADINTCNT	.DB	0
 	OR	$FF			; SIGNAL INTERRUPT HANDLED
 	RET
 ;
+; Z280 BAD INT HANDLER
+;
+#IF (MEMMGR == MM_Z280)
+;
+Z280_BADINT:
+	CALL	NEWLINE
+	LD	DE,Z280_BADINTSTR
+	CALL	WRITESTR
+	POP	HL			; DUMP MSR
+	POP	HL			; GET RET ADR
+	CALL	PRTHEXWORDHL
+	DI
+	HALT
+;
+Z280_BADINTSTR	.TEXT	"\n\n*** Z280 BAD INT @$"
+;
+#ENDIF
+;
+; Z280 PRIVILEGED INSTRUCTION HANDLER
+;
+#IF (MEMMGR == MM_Z280)
+;
+Z280_PRIVINST:
+	EX	(SP),HL			; GET MSR, SAVE HL
+	LD	(HB_MSRSAV),HL		; SAVE IT
+	POP	HL			; RECOVER HL, POP STACK
+	EX	(SP),HL			; GET ADR, SAVE HL
+	
+	PUSH	AF
+	PUSH	BC
+	PUSH	DE
+	
+	.DB	$ED,$96			; LDUP	A,(HL)
+	INC	HL			; BUMP PAST PRIV INST
+	
+	;CALL	PC_LBKT
+	;CALL	PRTHEXBYTE
+	;CALL	PC_RBKT
+	
+	; HANDLE DI
+	CP	$F3			; DI?
+	JR	NZ,Z280_PRIVINST2
+	DI				; DO THE DI
+	JR	Z280_PRIVINSTX
+
+Z280_PRIVINST2:
+	; HANDLE EI
+	CP	$FB			; EI?
+	JR	NZ,Z280_PRIVINST_HALT
+	EI				; DO THE EI
+	JR	Z280_PRIVINSTX
+
+Z280_PRIVINST_HALT:
+	; SOMETHING ELSE, DIAGNOSE & HALT SYSTEM
+	
+	PUSH	HL
+	CALL	PC_LBKT
+	CALL	PRTHEXBYTE
+	.DB	$ED,$96			; LDUP	A,(HL)
+	CALL	PRTHEXBYTE
+	INC	HL
+	.DB	$ED,$96			; LDUP	A,(HL)
+	CALL	PRTHEXBYTE
+	CALL	PC_RBKT
+	POP	HL
+
+	CALL	NEWLINE
+	LD	DE,Z280_PRIVSTR
+	CALL	WRITESTR
+	DEC	HL
+	CALL	PRTHEXWORDHL
+	
+	DI
+	HALT
+
+Z280_PRIVINSTX:	
+	POP	DE
+	POP	BC
+	POP	AF
+	
+	EX	(SP),HL			; RECOVER HL, ADR TO STK
+	PUSH	HL			; SAVE HL
+	LD	HL,(HB_MSRSAV)		; GET SAVED MSR
+	EX	(SP),HL			; MSR TO STK, RECOVER HL
+	.DB	$ED,$55			; RETIL
+;
+HB_MSRSAV	.DW	0
+;
+Z280_PRIVSTR	.TEXT	"\n\n*** Privileged Instruction @$"
+;
+#ENDIF
+;
 ; COMMON API FUNCTION DISPATCH CODE
 ;
 ; ON ENTRY B IS API FUNCTION NUMBER AND C IS UNIT #
@@ -3931,13 +3747,55 @@ Z280_IVT:
 	.DW	0			; NMI MSR
 	.DW	0			; NMI VECTOR
 	.DW	$0000			; INT A MSR
-	.DW	0			; INT A VECTOR
-	.FILL	$50 - ($ - Z280_IVT),0	; SKIP TO SYS CALL TRAP VECTOR
-	.DW	$0000			; SYS CALL, NEW MSR (UPDATED @ RUNTIME)
-	.DW	Z280_SYSCALL		; SYS CALL, VECTOR ADR
-	.DW	$0000			; PRIV INST TRAP, NEW MSR
-	.DW	Z280_PRIVINST		; PRIV INST, VECTOR ADR
-	.FILL	$70 - ($ - Z280_IVT),0	; SKIP TO START OF NMI/INTA VECTORS
+	.DW	Z280_BADINT		; INT A VECTOR
+	.DW	$0000			; INT B MSR
+	.DW	Z280_BADINT		; INT B VECTOR
+	.DW	$0000			; INT C MSR
+	.DW	Z280_BADINT		; INT C VECTOR
+	.DW	$0000			; COUNTER/TIMER 0 MSR
+	.DW	Z280_BADINT		; COUNTER/TIMER 0 VECTOR
+	.DW	$0000			; COUNTER/TIMER 1 MSR
+	.DW	Z280_BADINT		; COUNTER/TIMER 1 VECTOR
+	.DW	0, 0			; RESERVED
+	.DW	$0000			; COUNTER/TIMER 2 MSR
+	.DW	Z280_BADINT		; COUNTER/TIMER 2 VECTOR
+	.DW	$0000			; DMA CHANNEL 0 MSR
+	.DW	Z280_BADINT		; DMA CHANNEL 0 VECTOR
+	.DW	$0000			; DMA CHANNEL 1 MSR
+	.DW	Z280_BADINT		; DMA CHANNEL 1 VECTOR
+	.DW	$0000			; DMA CHANNEL 2 MSR
+	.DW	Z280_BADINT		; DMA CHANNEL 2 VECTOR
+	.DW	$0000			; DMA CHANNEL 3 MSR
+	.DW	Z280_BADINT		; DMA CHANNEL 3 VECTOR
+	.DW	$0000			; UART RECEIVER MSR
+	.DW	Z280_BADINT		; UART RECEIVER VECTOR
+	.DW	$0000			; UART TRANSMITTER MSR
+	.DW	Z280_BADINT		; UART TRANSMITTER VECTOR
+	.DW	$0000			; SINGLE STEP TRAP MSR
+	.DW	Z280_BADINT		; SINGLE STEP TRAP VECTOR
+	.DW	$0000			; BREAK ON HALT TRAP MSR
+	.DW	Z280_BADINT		; BREAK ON HALT TRAP VECTOR
+	.DW	$0000			; DIVISION EXCEPTION TRAP MSR
+	.DW	Z280_BADINT		; DIVISION EXCEPTION TRAP VECTOR
+	.DW	$0000			; STACK OVERFLOW WARNING TRAP MSR
+	.DW	Z280_BADINT		; STACK OVERFLOW WARNING TRAP VECTOR
+	.DW	$0000			; ACCESS VIOLATION TRAP MSR
+	.DW	Z280_BADINT		; ACCESS VIOLATION TRAP VECTOR
+	.DW	$0000			; SYSTEM CALL TRAP MSR
+	.DW	Z280_SYSCALL		; SYSTEM CALL TRAP VECTOR
+	.DW	$0000			; PRIVILEGED INSTRUCTION TRAP MSR
+	.DW	Z280_PRIVINST		; PRIVILEGED INSTRUCTION TRAP VECTOR
+	.DW	$0000			; EPU <- MEMORY EXTENDED INSTRUCTION TRAP MSR
+	.DW	Z280_BADINT		; EPU <- MEMORY EXTENDED INSTRUCTION TRAP VECTOR
+	.DW	$0000			; MEMORY <- EPU EXTENDED INSTRUCTION TRAP MSR
+	.DW	Z280_BADINT		; MEMORY <- EPU EXTENDED INSTRUCTION TRAP VECTOR
+	.DW	$0000			; A <- EPU EXTENDED INSTRUCTION TRAP MSR
+	.DW	Z280_BADINT		; A <- EPU EXTENDED INSTRUCTION TRAP VECTOR
+	.DW	$0000			; EPU INTERNAL OPERATION EXTENDED INSTRUCTION TRAP MSR
+	.DW	Z280_BADINT		; EPU INTERNAL OPERATION EXTENDED INSTRUCTION TRAP VECTOR
+	.DW	0, 0			; RESERVED
+	.DW	0, 0			; RESERVED
+	; PROGRAM COUNTER VALUES FOR NMI/INTA
 	.DW	HBX_IV00
 	.DW	HBX_IV01
 	.DW	HBX_IV02
@@ -3954,7 +3812,11 @@ Z280_IVT:
 	.DW	HBX_IV0D
 	.DW	HBX_IV0E
 	.DW	HBX_IV0F
-	.FILL	$370 - ($ - Z280_IVT),0	; FILL REMAINDER OF Z280 IVT
+	.FILL	(128 - 16) * 2, 0
+	; PROGRAM COUNTER VALUES FOR INTB
+	.FILL	128 * 2, 0
+	; PROGRAM COUNTER VALUES FOR INTC
+	.FILL	128 * 2, 0
 ;
 #ENDIF
 ;
@@ -4040,7 +3902,7 @@ W_MMU2:
 ;
 #ENDIF
 ;
-; Z280 BANK SELECTION (CALLED FROM PROXY)
+; Z280 BANK COPY (CALLED FROM PROXY)
 ;
 #IF (MEMMGR == MM_Z280)
 ;
diff --git a/Tools/unix/uz80as/uz80as.h b/Tools/unix/uz80as/uz80as.h
index 511da085..19e71764 100644
--- a/Tools/unix/uz80as/uz80as.h
+++ b/Tools/unix/uz80as/uz80as.h
@@ -8,7 +8,7 @@
 #ifndef UZ80AS_H
 #define UZ80AS_H
 
-int verbose;
+static int verbose;
 
 /* matchtab.flags */
 enum {