Emacs has always been able to split the screen, since long long before X support existed. (It calls the panes 'windows' and the GUI windows 'frames' because Emacs does everything differently.)
Emacs 24 can split the screen, both manually and automatically, in so many ludicrous ways I have not begun to explore the possibilities. (The window-management code was rewritten by Martin Rudalics, and the new code is... very flexible. Almost too flexible to understand.)