HalfNES vs NET-NES

HalfNES is a free NES and Famicom emulator for Linux, macOS, Windows, and other Java-compatible platforms. It supports the mapper numbers listed in its README, and says nearly all US releases will start, though some can show corrupted graphics or freeze. Its audio features include a sound core and an NSF player; display options include full screen and an NTSC filter. Controls can be remapped in Preferences, and joysticks work through DirectInput and xInput. HalfNES supports battery saves, but not savestates. GitHub releases provide a Windows executable and a JAR for other platforms, and both require Java 8 or newer. Linux users need to set execute permission on the JAR. Gamepads must be connected before a game loads to be detected, and their buttons cannot be configured. PAL games are supported but may have more issues; users need to select PAL in Preferences. The README gives a 2 GHz Athlon 64 or better as the requirement for full-speed play across all games, and notes that the NTSC filter needs substantially more processing power.

NET-NES is a free Nintendo Entertainment System emulator written in C# that can run some NES games. Downloadable builds are listed for Windows, macOS, and Linux, including win-x64, win-x86, osx-x64, osx-arm64, and linux-x64. Launching the executable opens a basic graphical interface with options to open a ROM and view the manual. Command-line options include ROM loading, a CPU JSON test, window scaling, an FPS counter, and debug mode. Mapper 0 is supported, while Mappers 1, 2, and 4 are implemented experimentally. The project says it passes nestest CPU instruction tests and lists tested games as working, but some games may glitch or freeze. Its PPU uses scanline timing rather than dot-by-dot timing, so it is not cycle accurate and some games may be affected. A debugger, Mapper 3, player 2 controller support, and audio are listed as upcoming features. The project distributes the software under the MIT License.