fixNES vs Nintendulator

fixNES is a free, open-source NES emulator for Windows and Linux. It runs NTSC and PAL .nes ROMs and creates .sav files for games that support saving. FDS and QD titles can run when a FDS BIOS named disksys.rom is placed in the same folder, and NSF music files are supported with track changes on the left and right keys. Files can be opened by drag and drop, command-line argument or from ZIP archives. The project lists support for NES mappers and VRC6, VRC7, FDS, MMC5, N163 and Sunsoft 5B audio expansions. Controls are keyboard-only; Windows users can use joy2key for controller input. The standalone build uses supplied scripts and requires freeglut and openal-soft, while a Makefile supports RetroArch core use. The README says the project is not in its most complete or cleanest state. It is licensed under MIT.

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.