Game Gear

To run homebrew or ROMs on your Game Gear you'll need a flashcart.

The only flashcart currently out for the Game Gear is the Everdrive GG

There are also some Chinese knockoff's that tend to be a copy of the original Everdrive GG

Beware of these units as they do not allow firmware update and updating will brick your unit. What you get at time of purchase is all you can expect.

Resellers
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