Hi for any old timers
You can actually emulate a real IBM mainframe with Linux these days
Here's a screenshot of me running TSO with 4 terminals ( I shown)
Response time on a Laptop is FAR FAR faster than back in the days when I actually ran TSO on a real IBM mainframe.
You can even run such old things as PL/I, Fortran and Cobol on it. !!!
(Shows some of us have more time than sense !!!!)
Anyway just a bit of Computing Nostalgia.