[Info-vax] OT: obscure PDP11 OSes (even more dinosaury)

[Alan Frisbie]

On 06/20/2015 02:04 PM, Stephen Hoffman wrote:
> On 2015-06-20 20:29:30 +0000, Hans Vlems said:
>
>> My question was whether the 11/20 had support for 18 bit addresses. I thought that the 11/20 was the only model limited to a 2^16 address space.
>
> The <http://gunkies.org/wiki/PDP-11> and <http://hampage.hu/pdp-11/main.html> pages indicate not; that there were other boxes that used 16 bits of the 18 bit UNIBUS.


Just for the record, there was a CSS (Computer Special Systems)
version (or add-on) for the PDP-11/20 to implement 18-bit addressing.
It was totally incompatible with later 18-bit addressing implementations.
I never actually saw one, just the manual for it.   I suspect that
only a handful (if that) were ever sold.

Alan Frisbie