The RSX command to run the front-end is: |M4FE
It's done in asm with custom text printing routines, so it's very fast. Immediate to run, browse folders or run games.
It supports up to 2048 files per folder, it supports joystick (two buttons). It remembers the last visited folder when moving back to the previous folder or when resetting the CPC via "CPC RESET" button in the M4. That's useful for reviewing series of games without having to navigate to them every time. To turn your M4 equipped CPC into a game console just put the |M4FE command in the AUTOEXEC.BAS file and run your favorite games using the joystick.
The ROM has been tested on CPC464, CPC6128 and 6128+. If someone has a CPC664 or a 464+ with a M4 I'd be very grateful if he can try it to check if it works.
Comments or suggestions are also welcome.
Abalore , CPCWIKI