The Libretro TGB Dual core emulates two Game Boys connected by a Game Link cable. That is what lets you play Tetris head-to-head, trade Pokémon, or take on a friend in any of the games that used the cable back in the day.
Recalbox fully automates the most common case. The trickier setups — two different games, or even two different systems — need a few manual steps, described below.
Game Boy and Game Boy Color are emulated by default with Libretro Gambatte. TGB Dual is only used for two-player sessions; the
gamelinkfolder is what triggers the switch automatically.
gamelink folderThe gb and gbc systems each contain a gamelink folder, created automatically. Anything placed in it is launched with TGB Dual, with no configuration at all.
/recalbox/share/roms/gb/gamelink (or gbc/gamelink).gamelink folder and launch the game.The screen splits automatically: both Game Boys are displayed side by side, one per player, linked by the emulated cable. Each player drives the console on their side with their own controller.
In this "one game, two Game Boys" mode, the second Game Boy's save is not handled. If you need both saves — to trade Pokémon, for instance — use the two-game mode below.
Using two separate copies of the game gives each player their own save. That requires manually loading both cartridges through RetroArch's subsystem mechanism.
gamelink folder of the system involved (gb or gbc).HOTKEY + B.Back once, then enter Subsystems.Load 2 Player Game Boy Link ★ and the line Current Content: GameBoy #1. Pick that option and select the first game.Subsystems: the line now reads Current Content: GameBoy #2. Pick the option again and select the second game.Subsystems one last time and run Start 2 Player Game Boy Link ★.The emulator restarts with both games loaded.
If your games are inside
.ziparchives, you have to browse the archive and then open the rom it contains. Extracting them beforehand is far simpler.
To pair a Game Boy game with a Game Boy Color one, an extra step applies: both saves must sit in the same folder before launching.
If you start from the Game Boy Color system, move the Game Boy game's save from /recalbox/share/saves/gb to /recalbox/share/saves/gbc — and the other way round if you start from the Game Boy.
For instance, for the game Pokemon - Blue Version (USA, Europe) (SGB Enhanced) in the gb folder, move Pokemon - Blue Version (USA, Europe) (SGB Enhanced).srm and .rtc to /recalbox/share/saves/gbc. Once the session is over and the emulator closed, put those files back where they belong.
Then follow the procedure described above.
Since Recalbox 10.1, TGB Dual supports netplay: you can play two linked Game Boys with someone who is not in the same room.
A dedicated core option, Force netplay state sync, forces state synchronisation between the two emulated Game Boys (the first being mirrored onto the second). Enable it from HOTKEY + B > Core Options if the session drifts out of sync.
As always in netplay, both players must use exactly the same rom — hence the value of a No-Intro set.