On Wed, 15 Nov 2000, Johnny Billquist wrote:
> On Tue, 14 Nov 2000, John Hayward wrote:
> 
> > > The PDP-11 is a 16 bit machine, period. That means you can only address
> > > 64k bytes. Nothing strange about that.
> >
> > As I recall some PDP-11s (11/70 I believe) had an instruction/data space
> > separate mapping so that your instructions could be in 1 64k area and your
> > data in another.

You had 3 64Kbyte (32K word) address spaces: Instruction, data and supervisor,
The supervisor space was used to hold libraries. There were extensive overlays
in the programs, the largest I saw IIRC was over 900 blocks (512 byte).
RSX-11M+ was capable of handling the 3 address spaces.

> 
> Correct. And it's a number of models, not just the 11/70. From my head:
> 11/45, 11/50, 11/55, 11/70, 11/74, 11/44, 11/53, 11/73, 11/83, 11/84,
> 11/93, 11/94.

I do not have such a good memory :-) But form this list 11/45 only can address
124Kword (248Kbyte) memory, so even if it had this abilty, it would could not
be used too well. 11/44 and 11/70 had 22 bit memory addressing (I do not know
the rest off hand).