extended file names

[Guy Harris]

>I assume that one can mix and match (have both enabled at one time).

Yes, you can plug in as many file system types as fit in physical memory
(i.e., if you have 128 MB worth of file system type code, you may have a
problem :-)), and at least at the kernel level they should all work. 
The file systems I know of that come with S5R4 are S5FS (the old
V7-derived file system), UFS (the new 4.3BSD-derived file system), NFS,
RFS, "/proc", and "/dev/fd"; there may be others.  Silicon Graphics, for
instance, would probably provide their Extent File System if, as, and
when they do an S5R4 port.

There are also mechanisms for allowing multiple file system types to be
handled by "mount", "fsck", etc., involving replacing those programs
with "drivers" that run file-system-specific versions.

So unless somebody's screwed something up, you should be able to run
both.  The only headaches I expect would be those involved with booting;
I don't know whether the various boot programs will be able to read
"/unix" off of either an S5 or UFS file system, or whether they'll only
be able to cope with one or the other.