/23+, no?  The basic 23 doesn't have an MMU, I'm pretty sure.

On Thu, Dec 5, 2024 at 11:58 AM Ron Natalie <ron@ronnatalie.com> wrote:

I remember on MiniUnix (a stripped down kernel that would run on PDP11’s
without memory management, in our case 11/03, 11/20, and an older 11/40)
there were no kernel pipes (and limited process concurrency).
The shell used the aforementioned emulation of pipe by just running the
output of one process into a temporary file subsequently loaded as stdin
of the other.

We kind of put all that to bed when the 11/23s came out and we could run
our full up kernel on the micros.