nes-emu-ios

An NES emulator written in Swift for iOS / iPadOS / macOS / tvOS. The NES emulation code is heavily based off of fogleman's NES emulator in Go: https://github.com/fogleman/nes

Screenshots

This app uses the UIDocumentBrowserViewController for easy NES ROM (.nes) file browsing using the native Files app interface. During emulation, PPU output frames are converted to a CIImage and rendered to a Metal Texture (MTLTexture) within a MetalKit View (MTKView). The app uses AVAudioEngine for sound, with buffers scheduled periodically from the APU output. Save states are persisted using CoreData. Everything is done using native iOS frameworks, and no third-party libraries.

Current Features

6502 CPU emulation
PPU emulation (picture processing unit)
APU emulation (audio processing unit)
Mapper emulation for several common mappers
Touchscreen controls
Save states with autosave on exit, and automatic loading of most recent save on game start. Automatic saving and loading can be enabled or disabled in the settings. The data structure of states may change slightly for future builds, so if you build from an updated source, you may need to erase existing save states or uninstall the previous version.
Gamepad controls using built-in GameController framework and extendedGamepad profile. MFi controllers, Sony DualSense / DualShock 4, or Xbox Wireless controllers should all work. Touchscreen controls auto-hide when a controller is paired for player 1, and auto-show when the player 1 controller disconnects. Whenever a second controller is paired, it should be mapped automatically for player 2.
Builds successfully for iOS 14.7+, iPadOS 14.7+, tvOS 14.7+, or Mac Catalyst (macOS 12.0 Monterey or newer). The Mac Catalyst version of the app still needs some Mac-specific tweaks. The tvOS version does not include the UIDocumentBrowserViewController for ROM browsing, because it is unavailable on the tvOS platform. For now, ROMs must be included directly in the tvOS app bundle before building and installing onto a device (copied to /nes-emu-tvos/Resources/, and added to the nes-emu-tvos build target).

Game Compatibility

The following mappers have been implemented:

000 NROM
001 MMC1
002 UNROM
003 CNROM
004 MMC3
005 MMC5 (missing some features)
007 AxROM
009 MMC2
010 MMC4
011 ColorDreams
023 VRC2b / VRC4e / VRC4f
025 VRC2c / VRC4b / VRC4d
040 NTDEC2722
066 GxROM
078 Mapper 78
085 VRC7 (missing expansion audio)
087 Mapper 87
118 TxSROM
119 TQROM
206 Namcot 118 / Tengen Mimic 1
232 Camerica Quattro

The majority of games should work with the above list of supported mappers, with more supported mappers coming soon.

Performance

For best performance, build the app for release mode instead of debug. Or, if you want better performance for debug builds, change these debug build settings under Swift Compiler - Code Generation:

Disable Safety Checks = YES
Exclusive Access to Memory = Compile Time Enforcement Only
Optimization level = Optimize for Speed [-O]

Near Future Plans