[TUHS] pdp11 UNIX memory allocation. Was: termcap vs terminfo (was: I swear! I rtfm'ed)

[Clem Cole]

Depends the processor.   For the 11/45 class processors, you had a 17th
address bit, which was the I/D choice.  For the 11/40 class you shared the
instructions and data space.  So you had to use overlays and thunks at lot
sooner.

On Tue, Jan 6, 2015 at 2:57 PM, Milo Velimirović <milov at cs.uwlax.edu> wrote:

> Bringing a conversation back online.
> On Jan 6, 2015, at 6:22 AM, arnold at skeeve.com wrote:
>
> >> Peter Jeremy scripsit:
> >>> But you pay for the size of $TERMCAP in every process you run.
> >
> > John Cowan <cowan at mercury.ccil.org> wrote:
> >> A single termcap line doesn't cost that much, less than a KB in most
> cases.
> >
> > In 1981 terms, this has more weight. On a non-split I/D PDP-11 you only
> > have 32KB to start with.  (The discussion a few weeks ago about cutting
> > yacc down to size comes to mind…)
>
> (Or even earlier than ’81.) How did pdp11 UNIXes handle per process
> memory? It’s suggested above that there was a 50-50 split of the 64KB
> address space between instructions and data. My own recollection is that
> you got any combination of instruction and data space that was <64KB. This
> would also be subject to limits of pdp11 memory management unit.
>
> Anyone have a definitive answer or pointer to appropriate man page or
> source code?
>
>
> Thanks,
> Milo
>
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