diff --git a/RomPatcher/patcher/Makefile b/RomPatcher/patcher/Makefile
index 49dd775..fcfc50e 100644
--- a/RomPatcher/patcher/Makefile
+++ b/RomPatcher/patcher/Makefile
@@ -10,7 +10,7 @@ YACC=bison -d #--report-file=bison.log --report=all
 CC=gcc
 CFLAGS=-O2
 
-all: patcher genlink
+all: patcher genlink sun3_checksum
 
 %.o: %.c
 	$(CC) $(CFLAGS) $< -c -o $@
@@ -21,6 +21,9 @@ patcher: $(PATCHEROBJ) $(OOBJ)
 genlink: $(GENLINKOBJ) $(OOBJ)
 	$(CC) $(CFLAGS) $^ -o $@
 
+sun3_checksum: sun3_checksum.c
+	$(CC) $(CFLAGS) $< -o $@
+
 parser_par.h: parser_par.o
 
 parser_par.o: parser_par.y
diff --git a/RomPatcher/patcher/sun3_checksum.c b/RomPatcher/patcher/sun3_checksum.c
new file mode 100644
index 0000000..8081159
--- /dev/null
+++ b/RomPatcher/patcher/sun3_checksum.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+
+int
+main ( int argc, char **argv )
+{
+  int fd, r;
+  unsigned char* adr = NULL;
+  struct stat st;
+  size_t size, i;
+  unsigned short int sum;
+
+  if (argc < 2) {
+    fprintf(stderr, "One argument needed: path to file to checksum\n");
+    exit(-1);
+  }
+  
+  fd = open(argv[1], O_RDONLY );
+  if (fd <= 0) {
+    fprintf(stderr, "Can't open file\n");
+    exit(-2);
+  }
+  r = fstat(fd, &st);
+  if (r < 0) {
+    fprintf(stderr, "Can't stat file\n");
+    exit(-3);
+  }
+  size = st.st_size;
+
+  adr = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0);
+  if (adr ==  MAP_FAILED) {
+    fprintf(stderr, "Can't mmap file\n");
+    exit(-3);
+  }
+
+  sum = 0;
+  for (i = 0 ; i < size-2 ; i++) {
+    sum += adr[i];
+  }
+
+  printf("Checksum is 0x%04x\n", sum);
+
+  return 0;
+}