Who wants to hear me make incorrect assumptions about old software? RSX is a system that, from the outside, can sound like it has a similar story to that of UNIX. First developed for the PDP-15 in 1969, RSX becomes much more well known when it migrates to the PDP-11. It becomes a multitasking and multiuser system. A key difference is niche. While UNIX is a very general purpose system RSX is built for real time. That leads to something very unique.