diff --git a/fw.py b/fw.py
index 12c7560..f2d7d14 100755
--- a/fw.py
+++ b/fw.py
@@ -2,11 +2,16 @@
 
 from uvk5 import UVK5, argv, eprint, Firmware
 
-def main(path):
-    fw = Firmware.load(path)
+def main(cmd):
     argc = len(argv)
+    fw = Firmware.load(argv[2])
+
     eprint('Version:', fw.version)
-    if argc >= 4 and argv[2] == 'mod':
+
+    if argc < 3:
+        return
+
+    if cmd == 'mod':
         eprint('mods:', argv[3])
         fw.apply_mods(argv[3].split(','))
         fw.write()
@@ -14,6 +19,13 @@ def main(path):
             with UVK5(argv[4]) as uvk5:
                 uvk5.get_version()
                 uvk5.send_firmware(fw)
+        return
+
+    if cmd == 'cmp':
+        fw2 = Firmware.load(argv[3])
+        fw.compare(fw2)
+
+
 
 if __name__ == '__main__':
     main(argv[1])
diff --git a/uvk5.py b/uvk5.py
index 5bb4601..0d5bd9f 100755
--- a/uvk5.py
+++ b/uvk5.py
@@ -104,6 +104,30 @@ class Firmware(bytearray):
         self.version = version
 
 
+    def compare(self, fw):
+        a = None
+        la = len(self)
+        lb = len(fw)
+        changes = {}
+        for i in range(min(la, lb)):
+            differ = self[i] != fw[i]
+            if not differ:
+                a = None
+                continue
+
+            if not a:
+                a = '0x%x' % i
+                changes[a] = [bytearray(), bytearray()]
+
+            changes[a][0].append(self[i])
+            changes[a][1].append(fw[i])
+
+
+        for addr, ch in changes.items():
+            print(addr, ch[0].hex(), ch[1].hex())
+
+
+
     def patch_single(self, addr, new_value, size=4):
         old_bytes = self[addr:addr+size]
         old_value = int.from_bytes(old_bytes, 'little')