<p>First of all, I don't need a textual comparison so Beyond Compare doesn't do what I need.</p>

<p>I'm looking for a util that can report on the differences between two files, at the byte level.  Bare minimum is the need to see the percentage change in the file, or a report on affected bytes/sectors.  </p>

<p>Is there anything available to save me the trouble of doing this myself?</p>

I guess it depends on what exactly is contained in the file, but here's a quick one:
```
```
hexdump file1 > file1.tmp
hexdump file2 > file2.tmp
diff file1.tmp file2.tmp
```
```
Since 16 bytes are typically reported on each line, this won't technically give you a count of the bytes changed, but will give you a rough idea where in the file changes have occurred.