The PDP-11 is inherently a 16-bit-pointer machine; it has no concept
of 32-bit pointers, so it is always either in the x86 small or the x86
tiny model.  

On DEC's operating systems, you could indeed set up overlays
that allowed code to be swapped in and out, either to disk or to unmapped
physical memory (much quicker!)  However, AFAIK ld(1) never provided that
capability to userspace, although the technique is used inside the kernel.
In any case, such tricks don't help with data space, which is strictly
limited to 64K.

--
There is / One art                      John Cowan <cowan@ccil.org>
No more / No less                       http://www.ccil.org/~cowan
To do / All things
With art- / Lessness