DOS and AIX might well be measures of your breadth, but unless your potential employer cares deeply about that, they don't do you much good. Think of some other way to say "I know a lot of different systems" than mentioning systems that don't garner much modern respect.

I don't mention that I used to frob PDP-11s, nor DOS, nor anything else. There are hints in my resume that I know that stuff, but I don't explicitly say it.

I think that mentioning dead technology creates a kind of taint. Sucks, but there you go.