On Mon, 6 Apr 2020 at 18:12, Warren Toomey <wkt@tuhs.org> wrote:
Anybody feel up for a bit of an archaeology challenge? Warner Losh is
currently poking through a bunch of bits but not having much luck decoding
them correctly. I've put a copy here: https://minnie.tuhs.org/Y5/Challenge/

If you can help, I'd suggest report major findings here, and we can use
the #TUHS channel in the ClassicCmp Discord server for chat.

Here's what Warner has found out so far:

   It's quite interesting, but in a 
   format I've so far not been able to decode more than with emacs.
   However, there's all kinds of wonderful here. This looks like it was a
   dump from a VMS (or maybe similar DEC OS) ANSI tape. There's 4 datasets
   of 2.5MB each.  The first one appears to be a V5 tree of some sort (at
   least it matches the V5 sources in places I can spot check in
   Dennis_v5. The second block looks v6ish or maybe pwbish, but no kernel
   sources. I don't think it's a continuation of the v5 stuff from the
   first dataset. The third dataset is all binaries, as far as I can tell
   so far, but things like mv and passwd. The 4th dataset appears to be
   the dump of a VENIX-11 system, complete with source.

   The 3rd dataset appears to be a Venix system. At least it has venix and
   venix.old in what looks like the root directory. Still trying to sort
   out extracting files from these datasets. v7fs hates them, but I'm
   almost positive that's what they are.

Looking at the first file as well as the later 512 byte files, this appears to have been made on an RT-11 system.  There are entries for HDR1ZEROED.ZZZ which shows up in the RT-11 5.07 sources: http://www.kpxx.ru/DEC/PDP-11/Software/OS/RT-11/05.07/05.07.abl/Unpacked/DUPZMC.MAC .  Unfortunately I have absolutely no experience with magtapes under RT-11 so I'm not currently sure how to proceed.