JGenesis Core on iPhone & iPad | Retropa

Systems and formats in the catalog

JGenesis upstream project: https://github.com/jsgroth/jgenesis — a single desktop codebase that grew to span several console generations. Retropa turns on only what its catalog lists, so treat the upstream README as background reading, not as a promise about this app. An extension is where you start, not a guarantee that a given title will run. Nothing is bundled either: no games, no BIOS files, and import only what you are entitled to use.

• Game Boy: .gb
• Game Boy Color: .gbc
• Game Boy Advance: .gba
• NES / Famicom: .nes
• SNES / Super Famicom: .sfc, .smc
• Sega Master System: .sms
• Game Gear: .gg
• Mega Drive: .md, .smd
• Genesis: .gen

Genesis and Mega Drive naming

North America called the console Genesis; Japan and Europe called it Mega Drive. Retropa's catalog carries entries under both names, which is why you may see the two sitting side by side. An extension is a clue about the image format, not a dependable region label, and a filename cannot tell you how a game expects to be timed. Leave the original file alone and confirm which system Retropa detected, rather than renaming it to pick a market.

Import for the right hardware

Put the image in Files first, let it finish downloading, then bring it in through the library. Before you press play, be sure you know which machine you are dealing with: Master System rather than Game Gear, NES / Famicom rather than SNES / Super Famicom. One core covering many systems still needs the right hardware path underneath. If the detected system looks wrong, sort out the file before you start adjusting display or controller settings.

• Master System and Game Gear are cousins, not the same machine.
• A format list for a whole system can be a union drawn from several cores.
• Everything on this page comes from Retropa's catalog, not from every feature upstream JGenesis offers.

Controls vary with the selected system

Genesis games want A, B and C, plus the extra six-button inputs when the layout offers them. Game Gear players should check Start; on Master System, look at the pause input. SNES layouts call for shoulder buttons that an NES layout never has. Prove a button combination works in a real scene before you decide the core dropped an input.

Core switching and keeping progress

On the Sega side there is usually nothing to switch to: the catalog names JGenesis as the only core for those cartridge systems. Plus opens the switching menu, but it cannot invent an implementation that was never in the catalog. Where an alternative does exist, it has to cover both your system and your file format before a comparison tells you anything. Retropa remembers your choice per game. Snapshot the in-game save and the first core's states, then run one scene on each core and judge sound, image and input for yourself.

• A save state records one core's internal state, and no other core can read it.
• In-game saves need their own backup, since no automatic migration is promised.
• Changing cores will not convert your game file or hand you a missing BIOS.

Sega coverage does not imply an alternate core

For its Sega cartridge systems, Retropa's catalog names JGenesis as the only core. Plus buys you switching where a second implementation exists; it does not conjure one that was never listed. The same caution applies to hardware: upstream support for disc images or add-ons does not mean those paths are wired into this app. Trust the catalog and what the app actually prompts you for.