unix developed on 11/20 with 20 on panel or machine that just said pdp/11?

[Paul Koning]

> On Jun 21, 2019, at 8:21 PM, Steve Malikoff via cctalk <cctalk at classiccmp.org> wrote:
> 
> Warren said
>> According to this page that Dennis Ritchie wrote, the original PDP-11
>> they used was indeed an 11/20 but it was before there were PDP-11 model
>> numbers:
>> 
>> https://www.bell-labs.com/usr/dmr/www/picture.html
>> 
>> And, of course, the PDP-7 Unix development came before the PDP-11 version :)
>> 
>> Cheers, Warren
> 
> It states that their 11/20 had a KS-11 memory management unit, was that mandatory for running v1 Unix on an 11/20?

Curious.  Recently on this list we learned that CSS built an MMU for the 11/20, rather different in structure from the later ones (not quite a Unibus peripheral but more in that direction).  But that wasn't called KS-11.

> The 1971 Unix Programmer's Manual mentions their 11/20 had 24 KB (surely KW?) memory rather than 28KW.
> https://www.bell-labs.com/usr/dmr/www/1stEdman.html

I would assume kW.  In the PDP11 world we didn't normally speak of bytes or kbytes, certainly not for memory and often not elsewhere either.  So we'd say the disks have 256 word blocks (except 32 in the RC11 and 1 in the RF11).

	paul