>Around the time of the lawsuit from Galoob, Nintendo tried to use other methods to thwart the Game Genie, using ROM checksums in later titles intended to detect the cheat modifications. These measures were partially successful but some could be bypassed with additional codes. Later versions of the Game Genie had the ability to hide Genie modifications from checksum routines.
Sega, on the other hand, was a full endorser of the Game Genie, with their official seal of approval.
I remember Nintendo saying they were blocking it due to ROM copiers.
The SNES Game Genie had a cool workaround where you could turn it on and off with a switch. So you'd put the codes in, turn it off, start the game, and turn it on.