Alright, this post should make clear the provocation for yesterday's digression into Pac-Man's bathroom habits. While Fletch and I were pondering the question, we both came across this site, where programmer Don Hodges says he has fixed the glitch that caused Pac-Man's split-screen bug at board No. 256.
A little history here. If you make it past board No. 255 (I forget which key this is). a subroutine error crashes the game, splitting its screen into one-half playable and the other garbled. Its algorithm is looking to draw a fruit that doesn't exist. This creates a perhaps unintentionally finite gameplay experience. It probably was a good thing. Every pattern has a hiding space where Pac-Man can pause, untouched, while the gamer takes a pee (or, snicker, a dump), eats, or does whatever. That's been a part of Pac-Marathons since day one. A truly infinite Pac-Man could lead to world records limited only by hardware integrity, probably going nonstop for months at a time.
Hodges fixes that, and offers proof of his work. Assuming you know how to go in and apply the patch yourself, voila, unlimited Pac-Man. (I guess he didn't include the ROM to avoid the copyright hassle). Of course, to get there you either have to use a MAME warp cheat — or know the patterns up to the 9th Key, memorably invoked in Buckner & Garcia's hit "Pac-Man Fever" and included with the liner notes.
Pac-Man's Split Screen Level Analyzed and Fixed