[TUHS] Can PDP-11/23 PLUS run Unix?

[Noel Chiappa via TUHS]

    > From: Clem Cole

    >> Why he started with the /70 version .. instead of the already extant
    >> /40 version

    > He didn't actually. 

The paper spends a lot of space, in Section 2.2 'Instruction Backup',
describing how to do instruction backup. Section 3 'Implementation of
PDP-11/34 UNIX' is not clear if he re-wrote that stuff; it lists "fault
handling" as something he did write (which could include instruction backup,
but might not). Instruction backup on machines without an MMR1 (like the /34)
was fully supported as of V5 (which supported the /40). Why all the attention
to instruction backup, if it was already done?


Also (unrelated to the above, but since I'm posting) use of overlays in the
kernel, useful on machines without separate I+D, came in with BSD 2.9:

  https://gunkies.org/wiki/2.9BSD

but it's poorly docuented; what I could find is linked there.

	Noel