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

[Jon Elson]

On 06/19/2019 08:23 PM, Bob Smith via cctalk wrote:
> My recollection, Unix on the 11 started with the 20 but because of the
> limited capabilties, it really was done on the /45.
> The three rings or 3 execution levels were not supported on the
> original machine.
>
MMU and expanded memory would be a great help in a 
multi-user system.  The original PDP-11 with 56 KB of memory 
was pretty limited.  Great for DOS-11 and RT-11, but more 
complex OS'es needed more resources.

Jon