diff --git a/tb_snes/snes-hirom.cfg b/tb_snes/snes-hirom.cfg
index 5a20506..147d5c6 100644
--- a/tb_snes/snes-hirom.cfg
+++ b/tb_snes/snes-hirom.cfg
@@ -1,6 +1,6 @@
 #
 # Attempts a proper layout for a SNES HiROM image
-#
+# This one is a 512kB (4Mbit) image
 
 #------------------------------------------------------------------------------
 #
@@ -13,7 +13,7 @@ MEMORY {
 	RAM:		start = $7e2000, size = $e000, type = rw, define = yes;
 	STACK:		start = $000000, size = $2000, type = rw, define = yes;
 	SRAM:		start = $006000, size = $2000, type = rw, define = yes;
-	MOREROM:	start = $410000, size = $10000, type = ro, file = %O, fill = yes, define = yes;
+	MOREROM:	start = $410000, size = $70000, type = ro, file = %O, fill = yes, define = yes;
 }
 #------------------------------------------------------------------------------
 #
diff --git a/tb_snes/tb1_snes.s b/tb_snes/tb1_snes.s
index facb73d..6bf9195 100644
--- a/tb_snes/tb1_snes.s
+++ b/tb_snes/tb1_snes.s
@@ -293,8 +293,10 @@ output:
         .byte   $01			; Country Code (1=NTSC,2=PAL)
 	.byte	$00			; License Code (0=unassigned)
         .byte   $00			; Version
-        .byte   $7f, $73, $80, $8c	; Unsigned 16-bit sum of ROM
-        .byte   $ff, $ff, $ff, $ff	; Complement of checksum
+        .word   $37f8		; Unsigned 16-bit sum of ROM
+        .word	$c807		; Complement of checksum
+
+	.word   $0,$0		; unknown?
 
 	; Interrupt Vectors!
 
diff --git a/tb_snes/tools/Makefile b/tb_snes/tools/Makefile
index fffe4da..8d223c3 100644
--- a/tb_snes/tools/Makefile
+++ b/tb_snes/tools/Makefile
@@ -5,7 +5,8 @@ LFLAGS =
 all:	bin2byte color_convert convert_font convert_font_bin \
 	dump_font make_pal pcx_to_sprite \
 	pcx_to_tiles_4bpp pcx_to_tiles_8bpp \
-	ansi_to_tile string_to_bytes convert_font_4bpp
+	ansi_to_tile string_to_bytes convert_font_4bpp \
+	snes_checksum
 	
 	
 ansi_to_tile:	ansi_to_tile.o
@@ -94,11 +95,18 @@ string_to_bytes.o:	string_to_bytes.c
 	$(CC) $(CFLAGS) -c string_to_bytes.c
 
 
+snes_checksum:	snes_checksum.o
+	$(CC) $(LFLAGS) -o snes_checksum snes_checksum.o
+
+snes_checksum.o:	snes_checksum.c
+	$(CC) $(CFLAGS) -c snes_checksum.c
+
+
 clean:	
 	rm -f *.o *~ bin2byte color_convert convert_font \
 		convert_font_bin dump_font make_pal pcx_to_sprite \
 		pcx_to_tiles_4bpp pcx_to_tiles_8bpp \
 		 ansi_to_tile string_to_bytes \
-		convert_font_4bpp
+		convert_font_4bpp snes_checksum
 
 
diff --git a/tb_snes/tools/snes_checksum.c b/tb_snes/tools/snes_checksum.c
new file mode 100644
index 0000000..af58b8f
--- /dev/null
+++ b/tb_snes/tools/snes_checksum.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+
+int main(int argc, char **argv) {
+
+   int byte;
+   unsigned int total=0;
+   unsigned short checksum;
+   
+   while(1) {
+      byte=fgetc(stdin);
+      if (byte<0) break;
+	
+      total+=byte;
+
+   }
+      
+   checksum=total&0xffff;
+   
+   printf("Checksum: %hx\n",checksum);
+   printf("Complement: %hx\n",~checksum);
+   
+   return 0;
+   
+   
+}
+
+   
\ No newline at end of file