Hope this helps........

I have been analyzing the files.

All the data files (programmes), appear to be derived from C or C++. So I dont think we can simply recode to avoid the checksum...that would be bad!

Anyhow ALL the files end 00xx xx xx. ie the last 3 bytes of the file apper to be the check sum.

This represent not a 16 bit or 32 bit checksum but a 24 bit checksum!

Having a wander around the web I did find a reference to the fact that OS-9 does use 24 bit CRC checking.

Therefore to me me it looks like the navboot files checksum is the last 3 bytes of the file itself.....

now all I have to do is to find a 24bit CRC calculator!

Good huntin'