Geolith vs NeoCD/PS2

Geolith is a free emulator for the Neo Geo AES, MVS, CD, and CDZ. It supports commercially released AES, MVS, and CD games, and runs on Linux, macOS, BSD, and Windows. Cartridge systems accept TerraOnion .NEO files; CD systems use .bin/.cue and can optionally use .chd images. BIOS files from a recent MAME set are required, with the needed archives varying by system. Geolith synchronizes its CPUs with the video and sound systems, though video event timing is best effort and cycle-accurate rendering remains a longer-term goal. Settings include system and BIOS mode, region, free play, memory card options, palette, and aspect ratio. Supported inputs range from Neo Geo joysticks to a Mahjong Controller, four-player extension board, V-Liner, and the Irritating Maze trackball. The project was written for The Jolly Good API and can be used in multi-emulator frameworks or standalone binaries. It does not support dedicated JAMMA PCB systems or PAL mode; an early Stakes Winner prototype is also unsupported because required data is missing.

NeoCD/PS2 is a free, open-source NeoGeo CD emulator for the Sony PlayStation 2. It is a port of NeoCD/SDL, adapted to replace SDL components with PS2-native libraries using PS2SDK. Games load directly from the CD-ROM. Video offers PAL/NTSC auto-detection and selection, while the in-game menu includes filtering, fullscreen video, and frameskip controls. The emulator supports two controllers, stereo sound emulation, and CDDA playback. NeoGeo CD memory card support uses 45 KB on a PS2 memory card. ZIP support is limited to the BIOS, and the NeoGeo CD BIOS is not included; users must find it or dump it from their own system. The releases page lists version 0.6c with CDDA fixes, including an auto-loop feature. Listed issues include sound problems when the frame rate is below full speed, timing issues, graphics glitches in some games, and needing to reset the PS2 to exit the BIOS. The project is distributed under GNU General Public License version 2 and says use is at the user's own risk; the README says it should only be used with games the user legally owns.