https://en.wikipedia.org/wiki/VAX#Virtual_memory_map
(although paging was in pdp-11 unix too, and neither was the 1st to have memory levels)
see also:
https://svnweb.freebsd.org/base/head/share/misc/bsd-family-t...
https://www.levenez.com/unix/
https://www.tuhs.org/