On 06/19/2019 08:23 PM, Bob Smith via cctalk wrote:
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.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.
Jon