diff --git a/ReadMe.md b/ReadMe.md
index 21ccd7d7..64d961a1 100644
--- a/ReadMe.md
+++ b/ReadMe.md
@@ -1038,7 +1038,7 @@ system, you can use the FLASH application to update your ROM. The
 following is a typical example of transferring ROM image using XModem
 and flashing the chip in-situ.
 
-    E>xm r rom.img
+    E>xm r rom.rom
     
     XMODEM v12.5 - 07/13/86
     RBC, 28-Aug-2019 [WBW], ASCI
@@ -1050,7 +1050,7 @@ and flashing the chip in-situ.
     
     Thanks for the upload
     
-    E>flash write rom.img
+    E>flash write rom.rom
     FLASH4 by Will Sowerbutts <will@sowerbutts.com> version 1.2.3
     
     Using RomWBW (v2.6+) bank switching.
@@ -1179,6 +1179,30 @@ images.
   - FAT.COM
   - TUNE.COM
 
+# System Update
+
+If the system running ROMWBW utilizes the SST39SF040 Flash chip then it is possible to do a System Update in place of
+a System Upgrade in some cases.
+
+A System Update would involve only updating the BIOS, ROM applications and CP/M system.
+
+A System Update may be more favorable than a System Upgrade in cases such as:
+
+ - Overwriting of the ROM drive is not desired.
+ - Space is unavailable to hold a full ROMWBW ROM.
+ - To mimimize time taken to transfer and flash a full ROM.
+ - Configuration changes are only minor and do not impact disk applications.
+
+The ROMWBW build process generates a system upgrade file along with the normal ROM image and can be identified by the
+extension ".upd". It will be 128Kb in size. In comparison the normal ROM image will have the extension ".rom" and be
+512Kb or 1024Kb in size.
+
+Transferring and flashing the System Update is accomplished in the same manner as described above in *Upgrading* with
+the required difference being that the flash application needs to be directed to complete a partial flash using the
+/p command line switch.
+
+`E>flash write rom.upd /p`
+
 # RomWBW Distribution
 
 All source code and distributions are maintained on GitHub. Code
diff --git a/Source/HBIOS/Build.ps1 b/Source/HBIOS/Build.ps1
index bd74126c..764efbe1 100644
--- a/Source/HBIOS/Build.ps1
+++ b/Source/HBIOS/Build.ps1
@@ -92,10 +92,11 @@ $ErrorAction = 'Stop'
 # Directories of required build tools (TASM & cpmtools)
 $TasmPath = '..\..\tools\tasm32'
 $CpmToolsPath = '..\..\tools\cpmtools'
+$LzaToolsPath = '..\..\tools\lzsa'
 
 # Add tool directories to PATH and setup TASM's TABS directory path
 $env:TASMTABS = $TasmPath
-$env:PATH = $TasmPath + ';' + $CpmToolsPath + ';' + $env:PATH
+$env:PATH = $TasmPath + ';' + $CpmToolsPath + ';' + $LzaToolsPath + ';' + $env:PATH
 
 # Initialize working variables
 $OutDir = "../../Binary"		# Output directory for final image file
@@ -105,6 +106,7 @@ $RomDiskFile = "RomDisk.tmp"		# Temporary filename used to create ROM disk image
 $RomFile = "${OutDir}/${RomName}.rom"	# Final name of ROM image
 $ComFile = "${OutDir}/${RomName}.com"	# Final name of COM image (command line loadable HBIOS/CBIOS)
 $ImgFile = "${OutDir}/${RomName}.img"	# Final name of IMG image (memory loadable HBIOS/CBIOS image)
+$UpdFile = "${OutDir}/${RomName}.upd"	# Final name of System ROM image 
 
 # Select the proper CBIOS to include in the ROM.  UNA is special.
 if ($Platform -eq "UNA") {$Bios = 'una'} else {$Bios = 'wbw'}
@@ -233,19 +235,30 @@ cpmchattr -f $RomFmt $RomDiskFile r 0:*.*
 # Finally, the individual binary components are concatenated together to produce
 # the final images.
 #
+$SystemFileList = "hbios_rom.bin", "osimg.bin", "osimg1.bin", "osimg.bin"
 if ($Platform -eq "UNA")
 {
 	Copy-Item 'osimg.bin' ${OutDir}\UNA_WBW_SYS.bin
 	Copy-Item $RomDiskFile ${OutDir}\UNA_WBW_ROM${ROMSize}.bin
 
 	Concat '..\UBIOS\UNA-BIOS.BIN','osimg.bin','..\UBIOS\FSFAT.BIN',$RomDiskFile $RomFile
+	Remove-Item $RomDiskFile
 }
 else 
 {
 	Concat 'hbios_rom.bin','osimg.bin','osimg1.bin','osimg.bin',$RomDiskFile $RomFile
 	Concat 'hbios_app.bin','osimg_small.bin' $ComFile
 	# Concat 'hbios_img.bin','osimg_small.bin' $ImgFile
+	Remove-Item $RomDiskFile
+	Set-Content $UpdFile -Value $null
+	foreach ($InputFile in $SystemFileList)
+	{
+		Copy-Item $InputFile $RomDiskFile
+#		lzsa -f2 -r $InputFile $RomDiskFile
+		Add-Content $UpdFile -Value ([System.IO.File]::ReadAllBytes($RomDiskFile)) -Encoding byte
+		Remove-Item $RomDiskFile
+	}
 }
 
 # Remove the temporary working ROM disk file
-Remove-Item $RomDiskFile
+#Remove-Item $RomDiskFile
diff --git a/Source/HBIOS/md.asm b/Source/HBIOS/md.asm
index 47160004..c03ac7cb 100644
--- a/Source/HBIOS/md.asm
+++ b/Source/HBIOS/md.asm
@@ -472,6 +472,7 @@ MD_SECM1:				; DESIRED SECTOR IS IN BUFFER
 ;
 MD_LBA4K	.DW	$FFFF		; LBA OF CURRENT SECTOR
 MD_FBAS		.DW	$FFFF		; BANK AND SECTOR
+;MD_FLOP		.DW	$FFFF		; ADDRESS OF LAST OPERATION CALLED
 #ENDIF
 ;
 ; READ RAM / ROM 
@@ -710,17 +711,18 @@ MD_PROBE:
 #ENDIF
 	PUSH	HL
 	CALL	MD_CALBAS		; SETUP BANK AND SECTOR
-	LD	HL,MD_FIDENT_R		; PUT ROUTINE TO CALL
+	LD	HL,MD_FIDEN_R		; PUT ROUTINE TO CALL
 	CALL	MD_FNCALL		; EXECUTE: IDENTIFY FLASH CHIP
 
 	LD	HL,MD_TGTDEV		; IF WE MATCH WITH
 	XOR	A			; A NON 39SF040
 	SBC	HL,BC			; CHIP SET THE
-	LD	A,(MD_FFSEN)		; R/W FLAG TO R/O
-	OR	H
-	OR	L			; A NON ZERO VALUE
-	LD	(MD_FFSEN),A		; MEANS WE CAN'T
-	POP	HL			; ENABLE FLASH WRITING
+	JR	Z,MD_PR2		; R/W FLAG TO R/O
+	LD	HL,MD_FFSEN		; A NON ZERO VALUE
+	SET	0,(HL)			; MEANS WE CAN'T
+					; ENABLE FLASH WRITING;
+MD_PR2:
+	POP	HL
 #IF (MD_FVBS==1)
 	CALL	MD_LAND			; LOOKUP AND DISPLAY
 #ENDIF
@@ -798,32 +800,32 @@ FF_NXT2:
 ;======================================================================
 ; COMMON FUNCTION CALL FOR:
 ;
-;  MD_FIDENT_R - IDENTIFY FLASH CHIP	
+;  MD_FIDEN_R - IDENTIFY FLASH CHIP	
 ;   ON ENTRY MD_FBAS HAS BEEN SET WITH BANK AND SECTOR BEING ACCESSED
-;            HL      POINTS TO THE ROUTINE TO RELOCATED AND CALLED
+;            HL      POINTS TO THE ROUTINE TO BE RELOCATED AND CALLED
 ;   ON EXIT  BC      CONTAINS THE CHIP ID BYTES.
 ;            A       NO STATUS IS RETURNED 
 ;
 ;  MD_FERAS_R - ERASE FLASH SECTOR	
 ;   ON ENTRY MD_FBAS HAS BEEN SET WITH BANK AND SECTOR BEING ACCESSED
-;            HL      POINTS TO THE ROUTINE TO RELOCATED AND CALLED
+;            HL      POINTS TO THE ROUTINE TO BE RELOCATED AND CALLED
 ;   ON EXIT  A       RETURNS STATUS 0=SUCCESS NZ=FAIL
 ;
 ;  MD_FREAD_R - READ FLASH SECTOR    
 ;   ON ENTRY MD_FBAS HAS BEEN SET WITH BANK AND SECTOR BEING ACCESSED
-;            HL      POINTS TO THE ROUTINE TO RELOCATED AND CALLED
+;            HL      POINTS TO THE ROUTINE TO BE RELOCATED AND CALLED
 ;            IX      POINTS TO WHERE TO SAVE DATA
 ;   ON EXIT  A       NO STATUS IS RETURNED
 ;
-;  MD_VERI_R - VERIFY FLASH SECTOR
+;  MD_FVERI_R - VERIFY FLASH SECTOR
 ;   ON ENTRY MD_FBAS HAS BEEN SET WITH BANK AND SECTOR BEING ACCESSED
-;            HL      POINTS TO THE ROUTINE TO RELOCATED AND CALLED
+;            HL      POINTS TO THE ROUTINE TO BE RELOCATED AND CALLED
 ;            IX      POINTS TO DATA TO COMPARE.
 ;   ON EXIT  A       RETURNS STATUS 0=SUCCESS NZ=FAIL
 ;
 ;  MD_FWRIT_R - WRITE FLASH SECTOR   
 ;   ON ENTRY MD_FBAS HAS BEEN SET WITH BANK AND SECTOR BEING ACCESSED
-;            HL      POINTS TO THE ROUTINE TO RELOCATED AND CALLED
+;            HL      POINTS TO THE ROUTINE TO BE RELOCATED AND CALLED
 ;            IX      POINTS TO DATA TO BE WRITTEN
 ;   ON EXIT  A       NO STATUS IS RETURNED
 ;
@@ -835,12 +837,22 @@ FF_NXT2:
 ;
 MD_FNCALL:				; USING HBX_BUF FOR CODE AREA
 ;
+;	EX	DE,HL			; IF WE ARE 
+;	LD	HL,(MD_FLOP)		; REPEATING THE
+;	XOR	A			; SAME OPERATION
+;	SBC	HL,DE			; AS PREVIOUS
+;	EX	DE,HL			; DONT COPY
+;	JR	Z,MD_FSAME		; IF THE SAME, DE=0
+;	LD	(MD_FLOP),HL		; SAVE CURRENT OPERATION FOR NEXT TIME
+
 	LD	DE,HBX_BUF		; EXECUTE / START ADDRESS
 	LD	BC,MD_CSIZE		; CODE SIZE. MAXIMUM 64 BYTES
 	LDIR				; COPY OUR RELOCATABLE CODE TO THE BUFFER
 ;
 	LD	D,B			; PRESET DE TO ZERO TO REDUCE
 	LD	E,B			; CODE SIZE IN RELOCATABLE CODE
+;
+;MD_FSAME:
 ;
 	LD	BC,(MD_FBAS)		; PUT BANK AND SECTOR DATA IN BC
 ;
@@ -891,7 +903,7 @@ MD_SAVSTK	.DW	0
 ;          NO STATUS IS RETURNED 
 ;======================================================================
 ;
-MD_FIDENT_R:				; THIS CODE GETS RELOCATED TO HIGH MEMORY
+MD_FIDEN_R:				; THIS CODE GETS RELOCATED TO HIGH MEMORY
 ;
 	LD	D,A			; SAVE CURRENT BANK
 ;
@@ -914,7 +926,7 @@ MD_FIDENT_R:				; THIS CODE GETS RELOCATED TO HIGH MEMORY
 ;
 ;	RET				
 ;
-MD_I_SZ	.EQU	$-MD_FIDENT_R		; SIZE OF RELOCATABLE CODE BUFFER REQUIRED
+MD_I_SZ	.EQU	$-MD_FIDEN_R		; SIZE OF RELOCATABLE CODE BUFFER REQUIRED
 ;
 ;======================================================================
 ; ERASE FLASH SECTOR. 
@@ -1189,7 +1201,7 @@ MD_FFSEN	.DB	00h		; FLASH FILES SYSTEM ENABLE
 ;======================================================================
 ;
 #IF (MD_FDBG==1)
-		.ECHO	"MD_FIDENT_R "
+		.ECHO	"MD_FIDEN_R "
 		.ECHO	MD_I_SZ
 		.ECHO	"\n"
 ;
@@ -1197,7 +1209,7 @@ MD_FFSEN	.DB	00h		; FLASH FILES SYSTEM ENABLE
 		.ECHO	MD_R_SZ
 		.ECHO	"\n"
 ;
-		.ECHO	"MD_VERI_R "
+		.ECHO	"MD_FVERI_R "
 		.ECHO	MD_V_SZ
 		.ECHO	"\n"
 ;
diff --git a/Tools/lzsa/lzsa.exe b/Tools/lzsa/lzsa.exe
index 1c1927d7..f7ad5895 100644
Binary files a/Tools/lzsa/lzsa.exe and b/Tools/lzsa/lzsa.exe differ