The original Bubble Bobble provides well-know cheat codes (e.g. "Power-up", "Original" mode, etc.).
In one guide, I've read that in order for them to work, the arcade need a dip switch to be enabled (or something like that).
Now, I think I couldn't find such dip switch in the emulated ROM I play with (on MAME), so I have a doubt: is such switch real, or it doesn't exist (and consequently, cheats were available on all the arcade Bubble Bobble machines)?