Quote Originally Posted by Mayhem View Post
It's because some PAL games are coded to refuse to work at 60Hz and instead you get the message on screen saying the game pack isn't designed for the system you're trying to play it on. Only on boot though. A SNES modded for 50/60Hz can be booted in 50Hz and then swapped to 60Hz afterwards on these games.
The thing is, I think some games work on clone systems, but others don't.

I've seen Super Mario Kart work on the Retro Duo, but when the American SNES version has trouble working, I'm not sure if it will.

Oh, and I'm pretty sure European NES games work on clone systems.