6386 <-> 3B1 floppy compatibility?

[Prentiss Riddle]

In article <1789 at cuuxb.ATT.COM>, rga at cuuxb.ATT.COM (Robert G. Arrigo) writes:
> 
> try the utility /etc/.cpiopc with the 'x' option. it knows all about
> unixpc formatted floppies.

Thanks for the tip!  I tried this out and was able to make it work, but
only one way.  Here's what I found. 

There is indeed an executable file "/etc/.cpiopc" on our AT&T 6386.  I
could find no trace of documentation for it on-line or in the manuals,
so I held my breath and ran it with no options.  It spat out:

    Usage: cpiopc -o[acvBwxyz0..5] <name-list [>collection]
           cpiopc -i[cdmrtuvfBKwxyz0..5] [-n user] [pattern ...] [<collection]

By experimentation I discovered that the -x option makes it use the
floppy drive as the input device (with -i) or the output device (with
-o), no matter how you may have input or output redirected. 

I was able to read a standard 3B1 install floppy on the 6386 using
"/etc/.cpiopc -icBvx". 

I couldn't make it work going the other direction, however.  I
formatted a floppy on the 3B1, inserted it in the 6386 and apparently
was able to write on it using the command "/etc/.cpiopc -ocBvx".  My
attempts to read the result on the 3B1 failed (I tried all variations
of /dev/[r]fp02[01]).

Does Robert Arrigo or anyone else by any chance have a "man" page or
other documentation on /etc/.cpiopc?  Or simply pointers on its use? 
And can anyone explain what this extremely important program is doing
hidden in /etc with a "." in front of its name?  Thanks. 

-- Prentiss Riddle ("Aprendiz de todo, maestro de nada.")
-- Opinions expressed are not necessarily those of my employer.
-- riddle%woton.uucp at cs.utexas.edu  {ihnp4,uunet}!ut-sally!im4u!woton!riddle