On Wed, Jun 19, 2024, 1:37 AM Dave Horsfall <dave@horsfall.org> wrote:

> Sort of between kernel and user mode, Unix [zillion trademarks etc] never
> used it. but did RSX-11?
>

2.11BSD used a mode between kernel and user for the TCP stack to get more
effective address space...

Warner

I used the latter long enough to hate it until Edition 5 arrived at UNSW,
> and I still remember being blown away by the fact that there was nothing
> privileged about the Shell :-)
>
> -- Dave
>