Just for what it's worth, I tried to explain the context and the historical importance when I wrote about the original discovery of the tape, and about the recovery:

https://www.theregister.com/2025/11/07/unix_fourth_edition_t...

https://www.theregister.com/2025/12/23/unix_v4_tape_successf...

Hi, this is me. I'm still hacking on it but ran into some hard to understand kernel bugs. once i mount more than the root filesystem (say /usr/man) there are issues with inode allocation/freeing. mixing and matching v4 and v5 stuff in various ways can also lead to other interesting bugs but often an allocated inode ends up on the freelist, and things break.

Otoh it's so much fun to hack and fiddle with the unix kernel :) very zen

This is the result of the tape from 1973 found at the University of Utah being sent over to the Computer History Museum for retrieval by bitsavers.org

Prior discussion: https://news.ycombinator.com/item?id=45840321

It still amazes me that even with all this functionality, it runs on a system with only 64k of RAM.

Has anyone managed to extract out the C source files and upload them into some browsable UI, e.g. GitHub or GitLab?