Link Cable

The Game Boy shipped in 1989 with a cable in the box. Nintendo called it the Video Link Cable at launch and the Game Link Cable within two years; it joined two machines for simultaneous two-player games, with Tetris as the demonstration, and from 1991 a Four Player Adapter extended it. Nine years later Pokémon built its design around the same socket: two editions with different monsters, so that completing a collection needed another player and a cable.

Fast facts

In the box: yes, from launch. “The Game Boy system comes complete with stereo headphones, a Video Link Cable and a great new version of the Soviet strategy game, Tetris” (Nintendo Power, 1989).
Name: “Video Link Cable” in 1989; “Game Link” by 1991, when Nintendo Power rated Game Boy titles “GL” (two players) or “GL-4” (up to four).
Four players: the “new Four Player Adapter”, reviewed with R.C. Pro-Am in June 1991.
What made it essential: Pokémon Red and Blue (North America 1998).

Two screens, two views

Nintendo’s launch pitch was that two linked machines gave each player their own screen, which a shared television could not: “Since there are two Screens, competitors see the action from their perspective. Tennis, for example, is always seen from an individual player’s own side of the court and, in Baseball, the pitcher has a view from the mound and the batter has a view from the plate.” Boxes carried a “Video Link Symbol” to mark games with simultaneous two-player play.

Tetris was the demonstration, and its two-player mode already had the shape later versus-puzzle games kept: “One important strategy is to transfer lines from your Game Boy to your opponent’s. For every two line completion of yours, one line will move over to your opponent. With a three line completion, two lines will transfer. With a Tetris, four lines will move over.”

British readers saw the link before they could buy the machine. Computer and Video Games in April 1990 listed it as the Game Boy’s biggest advance over earlier LCD handhelds — “most exciting of all, was the ability to link two Gameboys together for simultaneous two player action” — with UK release still months away.

How the link works

Each Game Boy has a serial port. When two are joined, one machine supplies the clock and the other follows it, and a byte moves in each direction for every eight clock pulses; the software on both sides agrees which is which. Games use that to swap small packets — positions, lines cleared, a monster’s data — a few times a frame. The exact timing and the register-level detail are in Nintendo’s licensee programming manual and in the community-written Pan Docs, and are not repeated here.

The Four Player Adapter of 1991 hung up to four machines off the same kind of port; Nintendo Power introduced it with R.C. Pro-Am — “use the new Four Player Adapter to connect Game Boys for three- or four-player fun” — and added a “GL-4” rating for games that supported it.

Pokémon

Nintendo Power previewed Pokémon in May 1998 with the cable as the hook: “the two editions will feature the exact same game, but not the same mix of monsters. While a particular monster may be common and easy to find in the Red edition of the game, it may be rare and much tougher to find in the Blue edition. Therefore, if you can’t locate a specific Pokémon in your Game Pak, you’ll have to go to another player with a different edition of the game to find it.” Duels ran over the same cable: “the victor will take home experience points”, but nothing could be captured that way.

By February 1999 the magazine was running a “Pokémon Link Cable Special”. Trading happened at an in-game “Cable Club” in any Pokémon Center once two machines were connected, and the design had one more reason to need a friend: “Some Pokémon evolve only after they are traded. If you have one of this type, you’ll have to trade it away to make it evolve, then trade again to get it back.”

Camera and Printer

The link was not only for games. The 1998 Game Boy Camera could “Game Link to another other Camera” to swap pictures, and printed to the Game Boy Printer, a separate peripheral on the same port; Nintendo Power called the combination a “Funtography studio” with tools “to doctor, develop, print and trade your photographs”.

Reception

Two years after launch the cable was familiar enough that Nintendo Power could ask readers “How often do you use Game Boy to Game Link with other players?” and run a letters page of “dream Game Link matches” against celebrities. The cable’s successors — the Game Boy Advance’s own link port and later wireless adapters — kept the same design idea, and Pokémon kept needing them.

Wired multiplayer