From: Dave Horsfall
Weren't V5/6/7/etc distributed as bootable tapes?
Set the switch register
to point to the tape instead of the disk...
Yes. See here:
https://gunkies.org/wiki/Installing_UNIX_Sixth_Edition
https://gunkies.org/wiki/Installing_Unix_Seventh_Edition
for the details of how it works.
Noel