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

[Jerry Eckert]

On 6/20/2015 9:02 PM, David Froble wrote:
> 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.
>>
>>  From the Things DECfolks Can't Unsee department: the new Dunkin
>> Donuts coffee shop color scheme looks like that of a PDP-11.
>>
>>
>
> The first PDP-11 I used was an 11/40.  I don't think it had more than 16
> bits of address space.  Could be wrong.  I seem to recall that the 11/40
> could run RSTS, but the 11/20 could not.  Top of the line at that time
> was the PDP-11/45.

RSTS-11 ran on the PDP-11/20; RSTS/E did not. The last version I recall 
running on the 11/20 was V4A (ca. 1973/74, when the hardware was 
replaced with a PDP-11/50).

My favorite hack on RSTS was creating files the system admins couldn't 
touch (until they figured out what I was doing...). RSTS stored file 
names in RAD50, which has several non-alphanumeric characters (space, ., 
$, and one other) in its character set; BASIC-Plus only accepted 
alphanumeric characters in file names. A MACRO program running in the 
RT-11 RTS could create or rename a file with the non-alphanumeric 
characters in the file name that would show up in a directory listing, 
but could not be opened using BASIC-Plus programs, which included all 
the RSTS CUSPs.