I once wrote a game, which used PAUSE to make some intended flickering of the screen (best visible on old TVs).
The game is inspired by Andre***'s game EROTICA, so it is also an "adult game" Confirm that you are older than 18 years, before downloading it from my ZX81 web-server (where it is stored as "hidden" file, so you cannot see it, when you display the directory, where it is stored).
General considerations, probably obvious to most of you:
The ZX81 ROM was designed to be also as a retrofit for the ZX80.
In a FAST mode only machine the only way to get something on the screen (excluding the MC tricks) is to enter in the "wait for a keypress" loop, which actually is the same code used by PAUSE. Its timing is critical and has to be also calibrated depending on the PAL/NTSC frame rate (detected by the software by the presence of a diode on the board).
The SLOW mode switches the computer in a parallel code loop: probably the "NEW ROM" just kept the PAUSE entry as it was: let's consider that they had only 8KB and serious space problems, otherwise they'd have rewritten at least the LOAD/SAVE routines !
