Hi Dave,
In theory, the 82077's supposed to be compatible with the 765, but it does
have a lot of extra baggage and some strange configuration modes that might
get in the way--particularly if there's floppy support built into the BIOS
extension ROM (I don't know if there is). I've got a floppy-only ISA
controller here with an 8473 on it (40 pin DIP package, not the AV SMT)
and, if you can suggest a test, I'll give it a go to determine if it might
be something peculiar to the Adaptec implementation.
Cheers,
Chuck