LYCOS RETRIEVER 
N64: Transfer Pak
built 668 days ago
[One] feature of the N64 controller is the ability to add options via an expansion slot on the bottom of the controller. A popular option is the Rumble Pak, which provides force feedback. This feature provides a tactile stimulation to certain actions in a game. For example, in a racing game, you might feel a jarring vibration as your car slams into the wall.
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Transfer Pak – an accessory that plugged into the controller and allowed the Nintendo 64 to transfer data between Game Boy and N64 games. Pokémon Stadium and Pokémon Stadium 2 are games that rely heavily on the Transfer Pak. Both Mario Golf and Mario Tennis ... made use of it. Rare's Perfect Dark was initially going to be compatible with the Transfer Pak in order to use pictures taken with the Game Boy Camera in the game, but this function was scrapped, and the Transfer Pak was usable only in combination with the Game Boy Color version of Perfect Dark for unlocking bonuses.
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Game information saved on a Controller Pak can be uploaded later to another N64 system. For example, if you are playing a basketball game, you can save your favorite team's statistics to a Controller Pak. You can then take your Controller Pak to a friend's house, upload your stats, and see whose team is better.
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Bio Sensor – An ear-clip that plugs into the Controller Pak slot of the N64 controller to measure the user's heart rate. Released only in Japan and compatible only with Tetris 64 where it will slow down or speed up the game depending on how fast the player's heart is beating.
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Transfer Pak