[TUHS] Split addressing (I/D) space (inspired by the death of the python... thread)

Noel Chiappa jnc at mercury.lcs.mit.edu
Sat Aug 5 07:40:50 AEST 2023

    > From: Clem Cole

    > first two subsystems for the 11 that ran out of text space were indeed
    > vi and Pascal subsystems 

Those were at Berkeley. We've established that S-I&D were in V6 when it was
released in May, 1975 - so my question is 'what was Bell doing in 1975 that
needed more than 64KB?'

The kernel, yeah, it could definitely use S-I&D on a larger system
(especially when you remember that stock V6 didn't play any tricks with
overlays, and also dedicated one segment - the correct term, used in the 1972
-11/45 processor manual - to the user structure, and one to the I/O page,
limiting the non-S-I&D kernel to 48KB). But what user commands?

It happens that I have a complete dump of one of the MIT systems, so I had a
look to see what _we_ were running S-I&D on. Here's the list from /bin (for
some reason that machine doesn't have a /usr/bin):


The lisp wasn't a serious use; I think the only thing we ever used it for was
'doctor'. So, two editors, a couple of language tools, an email tool (not
sure why that one got it - maybe for creating large outgoing messages). (The
ndd is probably to allow the biggest possible buffers.)

Nothing in /etc, and in /lib, just lint1 and lint2 (lint, AFAICT, post-dates
V6). Not a lot.

So now I'm really curious what Bell was using S-I&D for. (If I weren't lazy,
I'd pull the V6 distro - which is only available as RK images, and individual
files, alas - and look in /bin and everywhere and see if I can find anything.
I suspect not, though.)

Anyone have any guesses/suggestions? Maybe some custom applications?


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