[Info-vax] OT: IA-128 ???

[BillPedersen]

On Oct 18, 7:30 am, "P. Sture" <paul.nos... at sture.ch> wrote:
> In article
> <d19d4a6b-e7a0-47bc-b337-be2de56ba... at l9g2000yqi.googlegroups.com>,
>
>  BillPedersen <peder... at ccsscorp.com> wrote:
> > PDP-11/45, the second generation of PDP-11 was also a 16 bit processor
> > but it had a MMU to access up to 18 bits, so you could have 256KB of
> > memory, less the 8KB IO space.
>
> > PDP-11/70 introduced a MMU which was separated from the Unibus and
> > provided up to 22 bits memory addressing.  It was STILL at 16 bit
> > processor.
>
> Thanks Bill, I remember mention of 18 bits and 22 bits on an RSX course.
>
> We had an 11/34 with (IIRC) 192KB memory and running RT-11. It was with
> great satisfaction that I took out a load of overlays once we got the
> memory upgrade.
>
> --
> Paul Sture

Yes, being able to have a mapped environment rather than an unmapped
environment made a big difference. And getting to the point where
there was potentially 64 KB of "free" physical memory for a task/
program to run in made a big difference to how the program needed to
be structured as far as overlays.

Bill.