[Simh] pdp11 i/o addressing

[Rich Alderson]

> From: Timothe Litt <litt at ieee.org>
> Date: Fri, 16 Feb 2018 16:15:28 -0500

> Overlays were used to compensate for limited virtual address space.

ITYM "Overlays were used to compensate for limited address space."

I first encountered the notion of overlays in IBM 1401 and System/360 programs.
Neither computer had any notion of virtual memory, virtual addressing, memory
mapping, or any such hoohah.  You had the memory you were given, and that was
most decidedly that.

                                                                Rich

P. S. +3 Curmudgeon. :-)