HalfNES vs Nintendulator

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.

Nintendulator is a free, open-source Win32 NES emulator written in C++. It aims to reproduce NES hardware behavior, including quirks and special cases. Supported formats include .NES, UNIF, FDS images in fwNES format, and NSF; mapper support uses external DLLs, with extra sound channels available for most games that provide them. Features include FDS image writing, Game Genie codes, customizable controllers including four-player setups, input movie recording and playback, AVI capture, and a debugger with simple breakpoint support. Savestates and battery-backed RAM are stored in the current user's Application Data folder, so the emulator can run without administrator privileges. The official release listed is version 0.980, dated January 1, 2019. Version 0.985 Beta is an unstable development build that may have significant bugs. Versions 0.985 and later have 32-bit and 64-bit editions and are officially supported on Windows 10 and later; older Windows versions may work, and recent builds are tested with Wine. Full-speed emulation is estimated to require a 1500MHz or faster CPU.