Hi. I have this weird adaptor for the Megadrive / Genesis.
What I think it does, is add 'extra power' or additional buffer RAM or something like that.
I know this, because when I play something such as Sonic 2 without it, and drop 100 rings, the Megadrive lags out and the FPS drop. With it, this does not happen. I do not play with it, because if I bump it the game will freeze and it is not reliable as it is like a tower...
Here are some images of it.
It would be better, to just solder inside the Megadrive to the correct pins the chip for optimal performance and no more FPS drops...