Lion's chapter 6, has some stuff and exact but might not be what you are remembering, Chapter 13 of the BSD book is 'system startup' and more general than the Lions description. The other place I would suggest looking is the three DDJ articles Bill and Lynn Jolitz wrote; although he might have talked about the 386 specifics, not the vaxen/11.

On Wed, Apr 10, 2019 at 2:15 PM Erik E. Fair <fair-tuhs@netbsd.org> wrote:

That might well Chapter 6 "Getting Started" of the Lions Commentary on v6 Unix for the PDP-11. My nicely bound copy was published by Peer-to-Peer Communications in 1996.

https://www.peerllc.com/?optioncom_content&taskview&id &ItemidD

I'm not sure I know where my samizdat copy from UCB in the early 1980s is ...

Erik