The two ISO files named *_errors.iso had read errors.  In both cases,
the software.tar file in the image seems to be ok.  The *_errors.log
files show the kernel messages which were generated during read.

Somewhere in the RA4000 era, Bay/Nortel had a dumbass attack and
changed their version numbering scheme.  This resulted in some overlap
with previous versions.

The erpcd directories here are probably duplicated from stuff in the
iso or tar files, but include the assorted network loadable boot and
digimodem images.

The iso files dated 3/2016 _say_ unix on them, but contain WINNT
directories.

I believe the MIBS came from an ftp or web site.  Some of the bits are
in the iso or tar files too.

I used to mix and match boot images from different releases, depending
on the hardware in question.  By and large, erpcd will talk to most
versions of boot image.