Aucbvax.1816
fa.unix-wizards
utzoo!duke!decvax!ucbvax!CSVAX.mark@Berkeley
Thu Jun 18 15:39:58 1981
Re:  compatibility mode
The compat stuff was written primarily so zork and chess could run
on a vax.  We at Berkeley haven't tested it on anything else.
At Pittsburgh, where it was originally written, it's been tested
quite a bit more.

I can well imagine that the v6 restor program might not work n
a vax, given that the file systems are not in the same format.
But then, I've never looked at the insides of restor.