GnGeo vs NeoCD/SDLx Unleashed

GnGeo is a free NeoGeo emulator for Linux, with the project also describing possible support for other Unix systems. It runs NeoGeo ROM sets identified by their MAME names; the listed example starts Metal Slug with `gngeo mslug`. Command-line options include home, arcade, and unibios modes, as well as fullscreen display, scaling, interpolation, raster interrupts, blitters, and visual effects. Sound and joystick support, player controls, and hotkeys are configurable. Settings can be supplied on the command line or in user and per-game configuration files. The project describes graphical frontends with features such as game previews and configuration options. GnGeo requires SDL 1.2.x, libz, and a NeoGeo BIOS; NASM 0.98 is optional for i386 assembly optimization. Games must be ZIP files, while the BIOS must not be, and the default search location is `$prefix/share/gngeo/`. The README describes a source build using `./configure`, `make`, and `make install`. The repository lists no releases, and its licensing notes forbid commercial use of GnGeo as a whole because of included code and licensing.

NeoCD/SDLx Unleashed is a free Neo Geo CD emulator for the original Xbox. It runs many original Neo Geo CD games and reads real discs in ISO9660 format. The emulator does not support bin/cue or iso/mp3 images and requires an uncompressed 512 KB system BIOS named neocd.bin; the download page says a BIOS copy is permitted only for owners of an original Neo Geo CD console. It supports one or two players, full CDDA audio, region selection and memory cards. Display modes include 480p and 720p, selected according to dashboard settings. Video filters are AdvanceMame2x, Simple2x, SuperSai2x, SuperEagle and Scanline. Source code is released, and the download is a 448.6 KB ZIP attachment with no Digiex registration required. The page reports miscellaneous sound and timing issues and provides the program without warranty. The listed platform is the original Xbox. AES and MVS emulation, plus other related SNK arcade systems, are not supported.