DSP Magic Card
This is an example of a DSP plug-in cart for a SNES/SFC copier. The DSP chip is used in gamecarts found like Pilotwings and Super Mario Kart to enable those special graphics. A copier with a game loaded into its RAM can't emulate this chip because its a peice of hardware not software from the ROM, so a DSP plug-in must be in the cart slot of the copier so the game works. There are a number of different DSP chips so one won't work for all. There is no need to to go hunting for a cart like the one above, you can use game carts with the chip, you just need to find the right one.