diff --git a/Source/Doc/Architecture.md b/Source/Doc/Architecture.md
index 9b11978c..e3a3692d 100644
--- a/Source/Doc/Architecture.md
+++ b/Source/Doc/Architecture.md
@@ -2168,7 +2168,7 @@ IM1, the size of the table is the number of vectors chained together.
 For IM2, the size of the table is the number of slots in the vector
 table.
 
-#### SYSINT Subfunction 0x10) -- Get Interrupt (INTGET)
+#### SYSINT Subfunction 0x10 -- Get Interrupt (INTGET)
 
 |      _Entry Parameters_
 |           BC: 0xFC10
@@ -2182,7 +2182,7 @@ On entry, register E must contain an index into the interrupt vector
 table. On return, HL will contain the address of the current interrupt
 vector at the specified index.
 
-#### SYSINT Subfunction 0x20) -- Set Interrupt (INTSET)
+#### SYSINT Subfunction 0x20 -- Set Interrupt (INTSET)
 
 |      _Entry Parameters_
 |           BC: 0xFC20
@@ -2236,6 +2236,7 @@ Possible reasons a PANIC may occur are:
 
 - RAM Bank range error when attempting a read or write to a RAM disk.
 - Sector read function has not been setup but a read was attempted.
+- An interrupt vector has not been set up when an interrupt was received.
 - There was an attempt to add more devices than the device table had room for.
 - An illegal SD card command was encountered.
 
@@ -2244,21 +2245,30 @@ which section of the software or hardware caused the fault.
 
 ### SYSCHK 
 
-A syschk error is reported when an internal error is detected. The key differance 
-to the PANIC error is that execution may be continued. In which case an error 
-code is returned to the calling routine. The error code is not displayed at the console.
+A syschk error is identified when an internal error is detected. When this 
+occurs an error code is returned to the calling program in the A register.
+A non-zero result indicates an error.
+
+Syschk errors may be reported to the console. Whether this occurs depends on 
+the value of the diagnosis level equate DIAGLVL. By default syschk errors
+are not reported to the console.
+
+If the diagnosis level is set to display the diagnosis information, then
+memory address, register dump and error code is displayed.
+A key differance with the PANIC error is that execution may be continued. 
 
 Example error message:
 
-\>>> SYSCHK: @06C4[DFA3:DFC3:0100:F103:04FC:0000:2B5E] Continue (Y/N)
+\>>> SYSCHK: @06C4[DFA3:DFC3:0100:F103:04FC:0000:2B5E] FD
+Continue (Y/N)
 
-The format of the information provided is the same as with the PANIC report.
+The format of the information provided is similar the PANIC report.
 
-@XXXX [-AF-:-BC-:-DE-:-HL-:-SP-:-IX-:-IY-]
+@XXXX [-AF-:-BC-:-DE-:-HL-:-SP-:-IX-:-IY-] YY
 
-Syschk error codes are returned in the A register.
+The syschk error codes YY is returned in the A register.
 
-| Error                               | Code     |
+| Error                               | Code YY  |
 | ----------------------------------- | -------- |
 | Success                             |   0x00   | 
 | Undefined Error                     |   0xFF   | 
@@ -2305,7 +2315,7 @@ ROMWBW can be configured to display boot progress with the assistance of additio
 hardware. This take the form of an LED breakout debugging board connected to an
 8-bit output port. As the boot code executes, the LED output display is updated.
 
-To us an LED breakout board, it must be connected the computers data, reset and port
+To use a LED breakout board, it must be connected the computers data, reset and port
 select lines.
 
 To enable the DIAG option the following settings must be made in the systems .ini
diff --git a/Source/HBIOS/bqrtc.asm b/Source/HBIOS/bqrtc.asm
index 5bb10ec4..ce0daeb5 100644
--- a/Source/HBIOS/bqrtc.asm
+++ b/Source/HBIOS/bqrtc.asm
@@ -161,9 +161,7 @@ BQRTC_DISPATCH:
 	JP	Z, BQRTC_SETALM			; Set Alarm
 	DEC	A
 	JP	Z, BQRTC_DEVICE			; Report RTC device info
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC
-	OR	A
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 	
 ;
@@ -173,9 +171,7 @@ BQRTC_GETBYT:
 BQRTC_SETBYT:
 BQRTC_GETBLK:
 BQRTC_SETBLK:
-	CALL	SYSCHK
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 	
 ; RTC Get Time
diff --git a/Source/HBIOS/cfg_dyno.asm b/Source/HBIOS/cfg_dyno.asm
index 85454e5a..15434743 100644
--- a/Source/HBIOS/cfg_dyno.asm
+++ b/Source/HBIOS/cfg_dyno.asm
@@ -66,6 +66,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED (SINGLE LED)
 LEDMODE		.EQU	LEDMODE_STD	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_ezz80.asm b/Source/HBIOS/cfg_ezz80.asm
index 3b92f06d..ac048f40 100644
--- a/Source/HBIOS/cfg_ezz80.asm
+++ b/Source/HBIOS/cfg_ezz80.asm
@@ -67,6 +67,7 @@ WDOGIO		.EQU	$6F		; WATCHDOG REGISTER ADR
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED (SINGLE LED)
 LEDMODE		.EQU	LEDMODE_STD	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_master.asm b/Source/HBIOS/cfg_master.asm
index f9058025..699b1059 100644
--- a/Source/HBIOS/cfg_master.asm
+++ b/Source/HBIOS/cfg_master.asm
@@ -98,6 +98,7 @@ WDOGIO		.EQU	$6F		; WATCHDOG REGISTER ADR
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED (SINGLE LED)
 LEDMODE		.EQU	LEDMODE_STD	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_mbc.asm b/Source/HBIOS/cfg_mbc.asm
index 2dafc402..efea88c2 100644
--- a/Source/HBIOS/cfg_mbc.asm
+++ b/Source/HBIOS/cfg_mbc.asm
@@ -63,6 +63,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	TRUE		; ENABLES STATUS LED
 LEDMODE		.EQU	LEDMODE_RTC	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_mk4.asm b/Source/HBIOS/cfg_mk4.asm
index 39def02e..45e369e4 100644
--- a/Source/HBIOS/cfg_mk4.asm
+++ b/Source/HBIOS/cfg_mk4.asm
@@ -69,6 +69,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED (SINGLE LED)
 LEDMODE		.EQU	LEDMODE_STD	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_n8.asm b/Source/HBIOS/cfg_n8.asm
index 9e58d617..4f16c6a3 100644
--- a/Source/HBIOS/cfg_n8.asm
+++ b/Source/HBIOS/cfg_n8.asm
@@ -71,6 +71,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED
 LEDMODE		.EQU	LEDMODE_RTC	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_rcz180.asm b/Source/HBIOS/cfg_rcz180.asm
index 691ce1f9..29a5fe22 100644
--- a/Source/HBIOS/cfg_rcz180.asm
+++ b/Source/HBIOS/cfg_rcz180.asm
@@ -69,6 +69,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	TRUE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED (SINGLE LED)
 LEDMODE		.EQU	LEDMODE_STD	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_rcz280.asm b/Source/HBIOS/cfg_rcz280.asm
index d288a4c8..4dd10148 100644
--- a/Source/HBIOS/cfg_rcz280.asm
+++ b/Source/HBIOS/cfg_rcz280.asm
@@ -74,6 +74,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	TRUE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED (SINGLE LED)
 LEDMODE		.EQU	LEDMODE_STD	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_rcz80.asm b/Source/HBIOS/cfg_rcz80.asm
index 559a4987..946de68c 100644
--- a/Source/HBIOS/cfg_rcz80.asm
+++ b/Source/HBIOS/cfg_rcz80.asm
@@ -68,6 +68,7 @@ WDOGIO		.EQU	$6E		; WATCHDOG REGISTER ADR
 DIAGENABLE	.EQU	TRUE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED (SINGLE LED)
 LEDMODE		.EQU	LEDMODE_STD	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_rph.asm b/Source/HBIOS/cfg_rph.asm
index 20772210..bdedd3a9 100644
--- a/Source/HBIOS/cfg_rph.asm
+++ b/Source/HBIOS/cfg_rph.asm
@@ -69,6 +69,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED
 LEDMODE		.EQU	LEDMODE_RTC	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_sbc.asm b/Source/HBIOS/cfg_sbc.asm
index b5232098..8ede0b67 100644
--- a/Source/HBIOS/cfg_sbc.asm
+++ b/Source/HBIOS/cfg_sbc.asm
@@ -63,6 +63,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED
 LEDMODE		.EQU	LEDMODE_RTC	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_scz180.asm b/Source/HBIOS/cfg_scz180.asm
index 4f3ae86a..41e72dfb 100644
--- a/Source/HBIOS/cfg_scz180.asm
+++ b/Source/HBIOS/cfg_scz180.asm
@@ -64,6 +64,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	TRUE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$0D		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED (SINGLE LED)
 LEDMODE		.EQU	LEDMODE_STD	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_una.asm b/Source/HBIOS/cfg_una.asm
index 387acc1a..0041d1c8 100644
--- a/Source/HBIOS/cfg_una.asm
+++ b/Source/HBIOS/cfg_una.asm
@@ -32,3 +32,5 @@ ROMSIZE		.EQU	512		; SIZE OF ROM IN KB (MUST MATCH YOUR HARDWARE!!!)
 RTCIO		.EQU	$70		; RTC LATCH REGISTER ADR
 ;
 DSKYENABLE	.EQU	FALSE		; ENABLES DSKY (DO NOT COMBINE WITH PPIDE)
+
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
diff --git a/Source/HBIOS/cfg_zeta.asm b/Source/HBIOS/cfg_zeta.asm
index f5c70c5f..afc313b0 100644
--- a/Source/HBIOS/cfg_zeta.asm
+++ b/Source/HBIOS/cfg_zeta.asm
@@ -55,6 +55,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED
 LEDMODE		.EQU	LEDMODE_RTC	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cfg_zeta2.asm b/Source/HBIOS/cfg_zeta2.asm
index e5a657d7..5567b156 100644
--- a/Source/HBIOS/cfg_zeta2.asm
+++ b/Source/HBIOS/cfg_zeta2.asm
@@ -66,6 +66,7 @@ WDOGMODE	.EQU	WDOG_NONE	; WATCHDOG MODE: WDOG_[NONE|EZZ80|SKZ]
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
 DIAGDISKIO	.EQU	TRUE		; ENABLES DISK I/O ACTIVITY ON DIAGNOSTIC LEDS
+DIAGLVL		.EQU	DL_CRITICAL	; ERROR LEVEL REPORTING
 ;
 LEDENABLE	.EQU	FALSE		; ENABLES STATUS LED
 LEDMODE		.EQU	LEDMODE_RTC	; LEDMODE_[STD|RTC]
diff --git a/Source/HBIOS/cvdu.asm b/Source/HBIOS/cvdu.asm
index e2dcc4aa..b0dd0b7b 100644
--- a/Source/HBIOS/cvdu.asm
+++ b/Source/HBIOS/cvdu.asm
@@ -171,9 +171,7 @@ CVDU_VDADEV:
 	RET
 
 CVDU_VDASCS:
-	CALL	SYSCHK		; NOT IMPLEMENTED (YET)
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)	; NOT IMPLEMENTED (YET)
 	RET
 
 CVDU_VDASCP:
diff --git a/Source/HBIOS/ds7rtc.asm b/Source/HBIOS/ds7rtc.asm
index 262ca0af..34333554 100644
--- a/Source/HBIOS/ds7rtc.asm
+++ b/Source/HBIOS/ds7rtc.asm
@@ -100,9 +100,7 @@ DS7_DISPATCH:
 	JP	Z, DS7_SETALM			; SET ALARM
 	DEC	A
 	JP	Z, DS7_DEVICE			; REPORT RTC DEVICE INFO
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC
-	OR	A
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 ;
 ;-----------------------------------------------------------------------------
@@ -269,9 +267,7 @@ DS7_GETBLK:
 DS7_SETBLK:
 DS7_SETALM
 DS7_GETALM
-	CALL	SYSCHK
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 ;-----------------------------------------------------------------------------
 ; REPORT RTC DEVICE INFO
diff --git a/Source/HBIOS/dsrtc.asm b/Source/HBIOS/dsrtc.asm
index c4e8608b..be29dc5e 100644
--- a/Source/HBIOS/dsrtc.asm
+++ b/Source/HBIOS/dsrtc.asm
@@ -247,9 +247,7 @@ DSRTC_DISPATCH:
 	JP	Z,DSRTC_SETALM	; SET ALARM
 	DEC	A
 	JP	Z,DSRTC_DEVICE	; REPORT RTC DEVICE INFO
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC
-	OR	A
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 ;
 ; NVRAM FUNCTIONS ARE NOT AVAILABLE IN SIMULATOR
@@ -258,9 +256,7 @@ DSRTC_GETBLK:
 DSRTC_SETBLK:
 DSRTC_GETALM:
 DSRTC_SETALM:
-	CALL	SYSCHK
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 ;
 ; RTC GET TIME
diff --git a/Source/HBIOS/fd.asm b/Source/HBIOS/fd.asm
index 3e7bd1c0..17de8693 100644
--- a/Source/HBIOS/fd.asm
+++ b/Source/HBIOS/fd.asm
@@ -490,9 +490,7 @@ FD_FNTBL:
 FD_VERIFY:
 FD_FORMAT:
 FD_DEFMED:
-	CALL	SYSCHK			; INVALID SUB-FUNCTION
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)		; INVALID SUB-FUNCTION
 	RET
 ;
 ;
@@ -1149,9 +1147,7 @@ FD_RUN1:
 	JR	Z,FC_WRITE
 	CP	DOP_READID
 	JR	Z,FC_READID
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC
-	OR	A
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 
 FD_RUNCHK:
diff --git a/Source/HBIOS/gdc.asm b/Source/HBIOS/gdc.asm
index 1bd57ce4..8ddd7603 100644
--- a/Source/HBIOS/gdc.asm
+++ b/Source/HBIOS/gdc.asm
@@ -157,9 +157,7 @@ GDC_VDADEV:	; VIDEO DEVICE INFORMATION
 	RET
 ;
 GDC_VDASCS:	; SET CURSOR STYLE
-	CALL	SYSCHK		; NOT IMPLEMENTED (YET)
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 
 GDC_VDASCP:	; SET CURSOR POSITION
diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index 4bb00aa7..d640c3ed 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -53,6 +53,8 @@
 ;    - build.inc
 ;      - config/<plt>_<cfg>.asm
 ;        - cfg_<plt>.asm
+;      - [z180.inc|z280.inc]
+;      - [eipc.inc]
 ;  - <drivers>.asm
 ;  - <fonts>.asm
 ;  - util.asm
@@ -61,7 +63,7 @@
 ;  - decode.asm
 ;  - encode.asm
 ;  - [xio|mio].asm
-;  - dsky.asm
+;  - [dsky.asm|dskyng.asm]
 ;  - unlzsa2s.asm
 ;
 ; INCLUDE GENERIC STUFF
@@ -132,6 +134,11 @@ MODCNT	.SET	MODCNT + 1
 #DEFINE	LED(N)	\;
 #ENDIF
 ;
+#DEFINE SYSCHKERR(HB_ERR) \
+  #DEFCONT \	CALL	SYSCHKA
+  #DEFCONT \	LD	A,HB_ERR
+  #DEFCONT \	OR	A
+;
 ;
 ;
 #IF (INTMODE == 0)
@@ -1094,14 +1101,14 @@ HB_START:
 ;
 #IFDEF APPBOOT
   #IF (MEMMGR == MM_Z280)
-	LD	A,%00000001
+	LD	A,DIAG_01
 	OUT	(DIAGPORT),A
 	LD	DE,Z280_BOOTERR
 	LD	C,9
-	LD	A,%00000010
+	LD	A,DIAG_02
 	OUT	(DIAGPORT),A
 	CALL	$0005
-	LD	A,%00001000
+	LD	A,DIAG_04
 	OUT	(DIAGPORT),A
 	RET
 ;
@@ -1130,7 +1137,7 @@ Z280_BOOTERR	.TEXT	"\r\n\r\n*** Application mode boot not supported under Z280 n
 #ENDIF
 ;
 #IF (DIAGENABLE)
-	LD	A,%00000001
+	LD	A,DIAG_01
 	OUT	(DIAGPORT),A
 #ENDIF
 #IF (LEDENABLE)
@@ -1240,7 +1247,7 @@ Z280_INITZ:
 	LD	A,Z180_BASE
 	OUT0	($3F),A		; AT RESET, ICR IS AT $3F
 
-	DIAG(%00000010)
+	DIAG(DIAG_02)
 
 	; DISABLE REFRESH
 	XOR	A
@@ -1335,7 +1342,7 @@ Z280_INITZ:
 ; IS PERFORMED NEXT.
 ;
 #IF (DIAGENABLE)
-	LD	A,%00000011
+	LD	A,DIAG_02
 	OUT	(DIAGPORT),A
 #ENDIF
 ;
@@ -1663,7 +1670,7 @@ HB_START1:				; BNKCALL ARRIVES HERE, BUT NOW RUNNING IN RAM BANK
 	LD	SP,HBX_LOC - 2		; RESET STACK
 ;
 	; NOTIFY THAT WE MADE THE TRANSITION!
-	DIAG(%00000111)
+	DIAG(DIAG_03)
 	LED(%00000010)
 ;
 	; SET THE IN-RAM FLAG
@@ -1790,7 +1797,7 @@ SAVE_REC_M:
   #ENDIF
 #ENDIF
 ;
-	DIAG(%00001111)
+	DIAG(DIAG_04)
 ;
 #IF (WBWDEBUG == USEMIO)		; BUFFER OUTPUT UNTIL
 	CALL	MIO_INIT		; WE GET TO BOOT MESSAGE
@@ -1879,7 +1886,7 @@ HB_CPU1:
 ;
 #ENDIF
 ;
-	DIAG(%00011111)
+	DIAG(DIAG_05)
 ;
 ; INIT OSCILLATOR SPEED FROM CONFIG
 ;
@@ -2171,7 +2178,7 @@ Z280_TC	.EQU	CPUOSC / 4 / 50 / 2	; TIME CONSTANT
 	LD	A,$FF			; FILL WITH $FF
 	CALL	FILL			; DO IT
 ;
-	DIAG(%00111111)
+	DIAG(DIAG_06)
 ;
 #IF FALSE
 ;
@@ -2227,7 +2234,7 @@ NOT_REC_M0:
 ;
 #ENDIF
 ;
-	DIAG(%01111111)
+	DIAG(DIAG_07)
 	LED(%00000011)
 ;
 ;
@@ -2315,7 +2322,7 @@ NXTMIO:	LD	A,(HL)
 #ENDIF
 NOT_REC_M2:
 ;
-	DIAG(%11111111)
+	DIAG(DIAG_08)
 ;
 ; IO PORT SCAN
 ;
@@ -3128,7 +3135,7 @@ HB_DISPATCH:
 	PUSH	AF
 	LD	A,(HB_STACK - HB_STKSIZ + $08)
 	CP	$FF
-	CALL	SYSCHK
+	SYSCHKERR(ERR_INTERNAL)
 	LD	A,$FF
 	LD	(HB_STACK - HB_STKSIZ + $08),A
 	POP	AF
@@ -3156,9 +3163,7 @@ HB_DISPATCH1:
 	; FALL THRU
 ;
 HB_DISPERR:
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC
-	OR	A
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 ;
 ;==================================================================================================
@@ -3499,7 +3504,7 @@ HB_DSKFN:
 HB_DSKFNADR	.EQU	$+1
 	CALL	PANIC			; READ ONE SECTOR
 #IF (DIAGENABLE & DIAGDISKIO)
-	DIAG(0)				; CLEAR DIAG LEDS
+	DIAG(DIAG_00)				; CLEAR DIAG LEDS
 #ENDIF
 #IF (LEDENABLE & LEDDISKIO)
 	LED($00)
@@ -3620,9 +3625,7 @@ RTC_DISPATCH:
 	RET
 ;
 RTC_DISPERR:
-	CALL	SYSCHK
-	LD	A,ERR_NOHW
-	OR	A
+	SYSCHKERR(ERR_NOHW)
 	RET
 ;
 ; SET RTC DISPATCH ADDRESS, USED BY RTC DRIVERS DURING INIT
@@ -3820,9 +3823,7 @@ SYS_RESET:
 	JR	Z,SYS_RESCOLD
 	CP	BF_SYSRES_USER
 	JR	Z,SYS_RESUSER
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC
-	OR	A			; SIGNAL ERROR
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 ;
 ; SOFT RESET HBIOS, RELEASE HEAP MEMORY NOT USED BY HBIOS
@@ -4026,9 +4027,7 @@ SYS_ALLOC:
 ; ALL OTHER REGISTERS PRESERVED
 ;
 SYS_FREE:
-	CALL	SYSCHK			; NOT YET IMPLEMENTED
-	LD	A,ERR_NOTIMPL		; NOT YET INMPLEMENTED
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_NOTIMPL)		; NOT YET INMPLEMENTED
 	RET
 ;
 ; GET SYSTEM INFORMATION
@@ -4068,9 +4067,7 @@ SYS_GET:
 	JP	Z,SYS_GETBNKINFO
 	CP	BF_SYSGET_CPUSPD
 	JP	Z,SYS_GETCPUSPD
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC		; SIGNAL ERROR
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_NOFUNC)		; SIGNAL ERROR
 	RET
 ;
 ; GET TIMER
@@ -4157,7 +4154,7 @@ SYS_GETBNKINFO:
 	XOR	A
 	RET
 ;
-; GET SYSTEM CPU SPEED ORMANCE ATTRIBUTES
+; GET SYSTEM CPU SPEED PERFORMANCE ATTRIBUTES
 ;   RETURNS:
 ;     L: CLOCK MULT (0:HALF, 1:FULL, 2: DOUBLE)
 ;     D: MEMORY WAIT STATES
@@ -4362,9 +4359,7 @@ SYS_SET:
 	JR	Z,SYS_SETBOOTINFO
 	CP	BF_SYSSET_CPUSPD
 	JR	Z,SYS_SETCPUSPD
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC		; SIGNAL ERROR
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_NOFUNC)		; SIGNAL ERROR
 	RET
 ;
 ; SET BOOT INFORMATION
@@ -4725,9 +4720,7 @@ SYS_INT:
 	JR	Z,SYS_INTGET
 	CP	BF_SYSINT_SET
 	JR	Z,SYS_INTSET
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC		; SIGNAL ERROR
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_NOFUNC)		; SIGNAL ERROR
 	RET
 ;
 ; GET INTERRUPT SYSTEM INFORMATION
@@ -4753,9 +4746,7 @@ SYS_INTINFO:
 ;
 SYS_INTVECADR:
 #IF (INTMODE == 0)
-	CALL	SYSCHK			; INVALID FOR INT MODE 0
-	LD	A,ERR_BADCFG		; SIGNAL ERROR
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_BADCFG)		; SIGNAL ERROR. INVALID FOR INT MODE 0
 	RET
 #ENDIF
 #IF (INTMODE == 1)
@@ -4769,9 +4760,7 @@ SYS_INTVECADR:
 	LD	A,E			; INCOMING INDEX POSITION TO A
 	CP	C			; COMPARE TO VECTOR COUNT
 	JR	C,SYS_INTGET1		; CONTINUE IF POSITION IN RANGE
-	CALL	SYSCHK			; ELSE ERROR
-	LD	A,ERR_RANGE		; SIGNAL ERROR
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_RANGE)		; ELSE ERROR
 	RET
 SYS_INTGET1:
 	OR	A			; CLEAR CARRY
@@ -5252,15 +5241,11 @@ HB_DISPCALC:
 	RET				; JUMP TO DRIVER FUNC ADR ON TOS
 ;
 HB_FUNCERR:
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC		; SIGNAL ERROR
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_NOFUNC)		; SIGNAL ERROR
 	RET
 ;
 HB_UNITERR:
-	CALL	SYSCHK
-	LD	A,ERR_NOUNIT		; SIGNAL ERROR
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_NOUNIT)		; SIGNAL ERROR
 	RET
 ;
 ; ADD AN ENTRY TO THE UNIT TABLE AT ADDRESS IN HL
@@ -5347,9 +5332,7 @@ HB_ALLOC:
 HB_ALLOC1:
 	; ERROR RETURN
 	POP	DE			; RESTORE INCOMING DE
-	CALL	SYSCHK
-	LD	A,ERR_NOMEM		; SIGNAL ERROR
-	OR	A			; SET FLAGS
+	SYSCHKERR(ERR_NOMEM)		; SIGNAL ERROR
 	RET
 ;
 HB_TMPSZ	.DW	0
@@ -6337,7 +6320,7 @@ HB_RDSEC:
 ;
 ; SYSTEM CHECK: DUMP MACHINE STATE AND CONTINUE?
 ;
-SYSCHK:
+SYSCHKA:
 	; CHECK DIAG LEVEL TO SEE IF WE SHOULD DISPLAY
 	PUSH	AF			; PRESERVE INCOMING AF VALUE
 	LD	A,(CB_DIAGLVL)		; GET DIAGNOSTIC LEVEL
@@ -6351,6 +6334,17 @@ SYSCHK:
 	CALL	WRITESTR		; PRINT IT
 	POP	DE			; RESTORE DE VALUE
 	CALL	XREGDMP			; DUMP REGISTERS
+
+	; DISPLAY ERROR CODE. IT IS AT RETURN ADDRESS+1 .. LD A,XX
+	EX	(SP),HL			; GET RETURN ADDRESS
+	INC	HL			; POINT TO THE ERROR CODE
+	PUSH	AF
+	LD	A,(HL)			; DISPLAY
+	CALL	PRTHEXBYTE
+	POP	AF
+	DEC	HL			; RESTORE RETURN ADDRESS
+	EX	(SP),HL
+;
 	JR	CONTINUE		; CHECK W/ USER
 ;
 SYSCHK1:
@@ -6891,7 +6885,7 @@ PS_PRTDEV:
 	CALL	PS_PAD			; PAD N SPACES (SPECIFIED IN A)
 	RET
 ;
-; PRINT DEVICE NMEMONIC, DEVTYP/NUM SPECIFIED IN DE
+; PRINT DEVICE MNEMONIC, DEVTYP/NUM SPECIFIED IN DE
 ;
 PS_PRTNUL:
 	LD	HL,PS_STRNUL
diff --git a/Source/HBIOS/hbios.inc b/Source/HBIOS/hbios.inc
index d5e69636..d0d59a42 100644
--- a/Source/HBIOS/hbios.inc
+++ b/Source/HBIOS/hbios.inc
@@ -156,6 +156,111 @@ ERR_TIMEOUT		.EQU	-11	; DEVICE TIMEOUT
 ERR_BADCFG		.EQU	-12	; INVALID CONFIGURATION
 ERR_INTERNAL		.EQU	-13	; INTERNAL ERROR
 ;
+; HBIOS DIAG OPTIONS
+;
+DIAG_PROG	.EQU	0		; PROGRESS BAR
+DIAG_STEP	.EQU	1		; STEP BAR
+DIAG_ASCII	.EQU	2		; 8-BIT ASCII 30H - 39H
+DIAG_BINARY	.EQU	3		; BINARY 00H - 09H
+DIAG_7SEG	.EQU	4		; 7-SEGMENT
+DIAG_FLASH	.EQU	5		; FLASH
+DIAG_TRIG	.EQU	6		; TRIGGER
+;
+DIAG_DISP	.EQU	DIAG_PROG	; DEFAULT
+;
+#IF (DIAG_DISP == DIAG_PROG)
+DIAG_00 .EQU 00000000B	
+DIAG_01 .EQU 00000001B 
+DIAG_02 .EQU 00000011B 
+DIAG_03 .EQU 00000111B 
+DIAG_04 .EQU 00001111B 
+DIAG_05 .EQU 00011111B 
+DIAG_06 .EQU 00111111B 
+DIAG_07 .EQU 01111111B 
+DIAG_08 .EQU 11111111B 
+DIAG_09 .EQU 11111111B   
+#ENDIF
+;
+#IF (DIAG_DISP == DIAG_STEP)
+DIAG_00 .EQU 00000000B	
+DIAG_01 .EQU 00000001B 
+DIAG_02 .EQU 00000010B 
+DIAG_03 .EQU 00000100B 
+DIAG_04 .EQU 00001000B 
+DIAG_05 .EQU 00010000B 
+DIAG_06 .EQU 00100000B 
+DIAG_07 .EQU 01000000B 
+DIAG_08 .EQU 10000000B
+DIAG_09 .EQU 11111111B
+#ENDIF
+;
+#IF (DIAG_DISP == DIAG_ASCII)
+DIAG_00 .EQU '0'	
+DIAG_01 .EQU '1'
+DIAG_02 .EQU '2' 
+DIAG_03 .EQU '3' 
+DIAG_04 .EQU '4'
+DIAG_05 .EQU '5'
+DIAG_06 .EQU '6' 
+DIAG_07 .EQU '7'
+DIAG_08 .EQU '8' 
+DIAG_09 .EQU '9' 
+#ENDIF
+;
+#IF (DIAG_DISP == DIAG_BINARY)
+DIAG_00 .EQU 0	
+DIAG_01 .EQU 1
+DIAG_02 .EQU 2
+DIAG_03 .EQU 3
+DIAG_04 .EQU 4
+DIAG_05 .EQU 5
+DIAG_06 .EQU 6
+DIAG_07 .EQU 7
+DIAG_08 .EQU 8
+DIAG_09 .EQU 9 
+#ENDIF
+;
+#IF (DIAG_DISP == DIAG_7SEG)
+;             abcdefg
+DIAG_00 .EQU 00000000B ; BLANK
+DIAG_01 .EQU 01111110B ; 0
+DIAG_02 .EQU 00110000B ; 1
+DIAG_03 .EQU 01101101B ; 2
+DIAG_04 .EQU 01111001B ; 3 
+DIAG_05 .EQU 00110011B ; 4
+DIAG_06 .EQU 01011011B ; 5
+DIAG_07 .EQU 00011111B ; 6 
+DIAG_08 .EQU 01110000B ; 7
+DIAG_09 .EQU 01111111B ; 8
+DIAG_10 .EQU 01110011B ; 9
+#ENDIF
+;
+#IF (DIAG_DISP == DIAG_FLASH)
+DIAG_00 .EQU 00000000B ; OFF	
+DIAG_01 .EQU 11111111B ; ON
+DIAG_02 .EQU 00000000B ; OFF	
+DIAG_03 .EQU 11111111B ; ON
+DIAG_04 .EQU 00000000B ; OFF	
+DIAG_05 .EQU 11111111B ; ON
+DIAG_06 .EQU 00000000B ; OFF	
+DIAG_07 .EQU 11111111B ; ON
+DIAG_08 .EQU 00000000B ; OFF	
+DIAG_09 .EQU 11111111B ; ON 
+#ENDIF
+;
+#IF (DIAG_DISP == DIAG_TRIG)
+DIAG_00 .EQU 11111111B ; ON	
+DIAG_01 .EQU 11111111B ; ON
+DIAG_02 .EQU 11111111B ; ON
+DIAG_03 .EQU 11111111B ; ON
+DIAG_04 .EQU 11111111B ; ON
+DIAG_05 .EQU 11111111B ; ON
+DIAG_06 .EQU 11111111B ; ON
+DIAG_07 .EQU 11111111B ; ON
+DIAG_08 .EQU 11111111B ; ON
+DIAG_09 .EQU 11111111B ; ON 
+#ENDIF
+;
 ; MEDIA ID VALUES
 ;
 MID_NONE	.EQU	0
diff --git a/Source/HBIOS/hdsk.asm b/Source/HBIOS/hdsk.asm
index 3526e330..172595a6 100644
--- a/Source/HBIOS/hdsk.asm
+++ b/Source/HBIOS/hdsk.asm
@@ -121,9 +121,7 @@ HDSK_FNTBL:
 HDSK_VERIFY:
 HDSK_FORMAT:
 HDSK_DEFMED:
-	CALL	SYSCHK			; INVALID SUB-FUNCTION
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)			; INVALID SUB-FUNCTION
 	RET
 ;
 ;
diff --git a/Source/HBIOS/ide.asm b/Source/HBIOS/ide.asm
index f43e4468..582ade02 100644
--- a/Source/HBIOS/ide.asm
+++ b/Source/HBIOS/ide.asm
@@ -461,9 +461,7 @@ IDE_FNTBL:
 IDE_VERIFY:
 IDE_FORMAT:
 IDE_DEFMED:
-	CALL	SYSCHK			; NOT IMPLEMENTED
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)			; NOT IMPLEMENTED
 	RET
 ;
 ;
diff --git a/Source/HBIOS/intrtc.asm b/Source/HBIOS/intrtc.asm
index 6602b3a3..cbb2184f 100644
--- a/Source/HBIOS/intrtc.asm
+++ b/Source/HBIOS/intrtc.asm
@@ -56,9 +56,7 @@ INTRTC_DISPATCH:
 	JP	Z,INTRTC_SETALM	; SET ALARM 
 	DEC	A
 	JP	Z,INTRTC_DEVICE	; REPORT RTC DEVICE INFO
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC
-	OR	A
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 ;
 ; NVRAM FUNCTIONS ARE NOT AVAILABLE IN SIMULATOR
@@ -69,9 +67,7 @@ INTRTC_GETBLK:
 INTRTC_SETBLK:
 INTRTC_GETALM:
 INTRTC_SETALM:
-	CALL	SYSCHK
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 ;
 ; RTC GET TIME
@@ -205,7 +201,7 @@ INTRTC_INT2:
 	JR	NZ,INTRTC_INTX		; NOPE, DONE
 	LD	(HL),0			; BACK TO YEAR ZERO
 INTRTC_INTX:
-	JP	SYSCHK
+	JP	PANIC
 INTRTC_VEC	.EQU	$-2
 ;
 ; CONVERT FROM BINARY BUF (HL) TO BCD BUF (DE)
diff --git a/Source/HBIOS/md.asm b/Source/HBIOS/md.asm
index f96a782c..8277468e 100644
--- a/Source/HBIOS/md.asm
+++ b/Source/HBIOS/md.asm
@@ -157,9 +157,7 @@ MD_FNTBL:
 MD_VERIFY:
 MD_FORMAT:
 MD_DEFMED:
-	CALL	SYSCHK			; INVALID SUB-FUNCTION
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)		; INVALID SUB-FUNCTION
 	RET
 ;
 ;
@@ -182,9 +180,7 @@ MD_CAP:					; ASSUMES THAT UNIT 0 IS RAM, UNIT 1 IS ROM
 	JR	Z,MD_CAP0		; UNIT 0
 	DEC	A			; TRY UNIT 1
 	JR	Z,MD_CAP1		; UNIT 1
-	CALL	SYSCHK			; INVALID UNIT
-	LD	A,ERR_NOUNIT
-	OR	A
+	SYSCHKERR(ERR_NOUNIT)		; INVALID UNIT
 	RET
 MD_CAP0:
 	LD	A,(HCB + HCB_RAMBANKS)	; POINT TO RAM BANK COUNT
diff --git a/Source/HBIOS/ppide.asm b/Source/HBIOS/ppide.asm
index 2b18f519..fd55cb1c 100644
--- a/Source/HBIOS/ppide.asm
+++ b/Source/HBIOS/ppide.asm
@@ -470,9 +470,7 @@ PPIDE_FNTBL:
 PPIDE_VERIFY:
 PPIDE_FORMAT:
 PPIDE_DEFMED:
-	CALL	SYSCHK			; NOT IMPLEMENTED
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)		; NOT IMPLEMENTED
 	RET
 ;
 ;
diff --git a/Source/HBIOS/ppp.asm b/Source/HBIOS/ppp.asm
index 7926da76..b5d740e6 100644
--- a/Source/HBIOS/ppp.asm
+++ b/Source/HBIOS/ppp.asm
@@ -338,9 +338,7 @@ PPPCON_OST:
 ;
 ;
 PPPCON_INITDEV:
-	CALL	SYSCHK
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 ;
 ;
@@ -504,9 +502,7 @@ PPPSD_FNTBL:
 PPPSD_VERIFY:
 PPPSD_FORMAT:
 PPPSD_DEFMED:
-	CALL	SYSCHK			; INVALID SUB-FUNCTION
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)		; INVALID SUB-FUNCTION
 	RET
 ;
 ;
diff --git a/Source/HBIOS/prp.asm b/Source/HBIOS/prp.asm
index 0f7f48bc..92bea67a 100644
--- a/Source/HBIOS/prp.asm
+++ b/Source/HBIOS/prp.asm
@@ -211,9 +211,7 @@ PRPCON_OST1:
 ;
 ;
 PRPCON_INITDEV:
-	CALL	SYSCHK
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 ;
 ;
@@ -401,9 +399,7 @@ PRPSD_FNTBL:
 PRPSD_VERIFY:
 PRPSD_FORMAT:
 PRPSD_DEFMED:
-	CALL	SYSCHK			; INVALID SUB-FUNCTION
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)		; INVALID SUB-FUNCTION
 	RET
 ;
 ;
diff --git a/Source/HBIOS/rf.asm b/Source/HBIOS/rf.asm
index 47d78238..17aa5305 100644
--- a/Source/HBIOS/rf.asm
+++ b/Source/HBIOS/rf.asm
@@ -138,9 +138,7 @@ RF_FNTBL:
 RF_VERIFY:
 RF_FORMAT:
 RF_DEFMED:
-	CALL	SYSCHK			; INVALID SUB-FUNCTION
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)		; INVALID SUB-FUNCTION
 	RET
 ;
 ;
diff --git a/Source/HBIOS/rp5rtc.asm b/Source/HBIOS/rp5rtc.asm
index 4fe0a677..df74a42d 100644
--- a/Source/HBIOS/rp5rtc.asm
+++ b/Source/HBIOS/rp5rtc.asm
@@ -159,9 +159,7 @@ RP5RTC_DISPATCH:
 	JP	Z,RP5RTC_SETALM		; SET ALARM
 	DEC	A
 	JP	Z,RP5RTC_DEVICE		; REPORT RTC DEVICE INFO
-	CALL	SYSCHK
-	LD	A, ERR_NOFUNC
-	OR	A
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 ;
 ; RTC GET NVRAM BYTE
@@ -240,9 +238,7 @@ RP5RTC_GETBLK:
 RP5RTC_SETBLK:
 RP5RTC_GETALM:
 RP5RTC_SETALM:
-	LD	A, ERR_NOTIMPL
-	CALL	SYSCHK
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 ;
 ; RTC GET TIME
diff --git a/Source/HBIOS/sd.asm b/Source/HBIOS/sd.asm
index e81baf5d..360e823b 100644
--- a/Source/HBIOS/sd.asm
+++ b/Source/HBIOS/sd.asm
@@ -710,9 +710,7 @@ SD_FNTBL:
 SD_VERIFY:
 SD_FORMAT:
 SD_DEFMED:
-	CALL	SYSCHK			; INVALID SUB-FUNCTION
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)		; INVALID SUB-FUNCTION
 	RET
 ;
 ;
@@ -1131,7 +1129,9 @@ SD_INITCARD5:
 	JR	SD_INITCARD6		; HANDLE MMC OR SDSC
 ;	
 SD_INITCARD5A:
-	CALL	SYSCHK
+	PUSH	AF
+	SYSCHKERR(ERR_NOMEDIA)
+	POP	AF
 	JP	SD_NOMEDIA
 ;
 ; CAPACITY CALCULATION FOR MMC OR SDSC (V1) CARDS:
diff --git a/Source/HBIOS/simrtc.asm b/Source/HBIOS/simrtc.asm
index f144d1aa..521b806d 100644
--- a/Source/HBIOS/simrtc.asm
+++ b/Source/HBIOS/simrtc.asm
@@ -55,9 +55,7 @@ SIMRTC_DISPATCH:
 	JP	Z,SIMRTC_SETALM	; SET ALARM 
 	DEC	A
 	JP	Z,SIMRTC_DEVICE	; REPORT RTC DEVICE INFO
-	CALL	SYSCHK
-	LD	A,ERR_NOFUNC
-	OR	A
+	SYSCHKERR(ERR_NOFUNC)
 	RET
 ;
 ; NVRAM FUNCTIONS ARE NOT AVAILABLE IN SIMULATOR
@@ -68,9 +66,7 @@ SIMRTC_GETBLK:
 SIMRTC_SETBLK:
 SIMRTC_GETALM:
 SIMRTC_SETALM:
-	CALL	SYSCHK
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)
 	RET
 ;
 ; RTC GET TIME
diff --git a/Source/HBIOS/sio.asm b/Source/HBIOS/sio.asm
index f1de029c..4342d9f2 100644
--- a/Source/HBIOS/sio.asm
+++ b/Source/HBIOS/sio.asm
@@ -843,9 +843,7 @@ SIO_INITGO:
 	LD	L,SIO1_VEC		; ASSUME CHIP 1
 	DEC	A			; CHIP 1?
 	JR	Z,SIO_INITIVT		; IF SO, DO IT
-	CALL 	SYSCHK			; IMPOSSIBLE SITUATION
-	LD	A,ERR_NOUNIT
-	OR	A
+	SYSCHKERR(ERR_NOUNIT)		; IMPOSSIBLE SITUATION
 	RET
 SIO_INITIVT:
 	LD	A,L			; VALUE TO A
diff --git a/Source/HBIOS/std.asm b/Source/HBIOS/std.asm
index e32a6fac..5bcb465f 100644
--- a/Source/HBIOS/std.asm
+++ b/Source/HBIOS/std.asm
@@ -56,11 +56,6 @@ BIOS_NONE	.EQU	0		; NO BIOS TYPE DEFINED
 BIOS_WBW	.EQU	1		; ROMWBW HBIOS
 BIOS_UNA	.EQU	2		; UNA UBIOS
 ;
-; DEFAULT HBIOS DIAGNOSTIC LEVEL
-;   WILL ULTIMATELY BE MOVED TO CONFIG FILE
-;
-DIAGLVL		.EQU	DL_CRITICAL
-;
 ; MEMORY MANAGERS
 ;
 MM_NONE		.EQU	0
diff --git a/Source/HBIOS/tms.asm b/Source/HBIOS/tms.asm
index 7282c8d7..90a7832f 100644
--- a/Source/HBIOS/tms.asm
+++ b/Source/HBIOS/tms.asm
@@ -298,9 +298,7 @@ TMS_VDADEV:
 	RET
 
 TMS_VDASCS:
-	CALL	SYSCHK		; NOT IMPLEMENTED (YET)
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)		; NOT IMPLEMENTED (YET)
 	RET
 
 TMS_VDASCP:
diff --git a/Source/HBIOS/vga.asm b/Source/HBIOS/vga.asm
index 61832ff4..d072711b 100644
--- a/Source/HBIOS/vga.asm
+++ b/Source/HBIOS/vga.asm
@@ -211,9 +211,7 @@ VGA_VDADEV:
 	RET
 
 VGA_VDASCS:
-	CALL	SYSCHK		; NOT IMPLEMENTED (YET)
-	LD	A,ERR_NOTIMPL
-	OR	A
+	SYSCHKERR(ERR_NOTIMPL)	; NOT IMPLEMENTED (YET)
 	RET
 
 VGA_VDASCP: