Geolith

Geolith is a free emulator for Neo Geo AES, MVS, CD, and CDZ systems. It best suits players who want one preservation-focused option across cartridge and disc games and can provide the required BIOS files. Its breadth and detailed settings are appealing, but best-effort video timing and support limits make it a less exact fit for every setup.

Overview

Geolith aims to emulate several core Neo Geo systems in one program, and its README says it is compatible with all commercially released AES, MVS, and CD games. It belongs to Jolly Good Emulation, a project focused on preservation, reusability, simplicity, and readable code. The BSD-3-Clause license and option to use Geolith as a standalone binary or within multi-emulator frameworks give it flexibility beyond a single front end. Compiling it requires The Jolly Good API's header files.

Key features

Geolith emulates CPUs at instruction-level granularity and synchronizes them with each other, the LSPC video system, and YM2610 sound. That synchronization is a meaningful foundation for accurate play, but video-event timing remains best effort rather than cycle-accurate. The project describes games as playable with minor differences from real hardware and no known major bugs; users seeking cycle-accurate rendering should look elsewhere for now.

Cartridge systems accept TerraOnion.NEO files only. CD systems support.bin/.cue images and optionally.chd, while BIOS files from a recent MAME set are required and the necessary archives vary by system. This is a capable combination for users with supported images and BIOS material, but the single cartridge format is a real constraint for other libraries.

Settings include AES, MVS, or Universe BIOS mode, CD system and region, free play, memory-card options, palette, and aspect ratio. Geolith also supports specialized inputs: Neo Geo joysticks, the Mahjong Controller, a four-player extension board, V-Liner, and the Irritating Maze trackball. That breadth matters to users preserving unusual control schemes, not just standard joystick play.

Pricing

Geolith is free, with no paid tier or free trial. There are no seat, quota, or renewal terms to weigh; its practical cost is the setup work of obtaining the required BIOS files and, for builders, The Jolly Good API headers.

Platforms

Geolith supports Linux, macOS, BSD, and Windows. The README gives build instructions for Linux, macOS, and BSD, and Windows builds use MSYS2. This range serves desktop users across the major operating systems, though it does not extend to mobile platforms.

Who it's for

Choose Geolith if you want AES, MVS, and Neo Geo CD support in one free emulator, value configurable system behavior and specialized controller support, and are comfortable managing BIOS files and supported image formats. It is less suitable if you need dedicated JAMMA PCB systems, PAL mode, or an early Stakes Winner prototype: those are not supported. The project also says cycle-accurate rendering remains a longer-term goal.

Pros and cons

Pros: Covers AES, MVS, CD, and CDZ, with compatibility stated for commercially released AES, MVS, and CD games.

Pros: Synchronizes instruction-level CPU emulation with video and sound, and offers settings for BIOS mode, region, memory cards, palette, and aspect ratio.

Pros: Supports several uncommon Neo Geo input devices, including the Mahjong Controller and Irritating Maze trackball.

Cons: Cartridge support is limited to TerraOnion.NEO files, and BIOS files from a recent MAME set are required.

Cons: Best-effort video-event timing is short of cycle-accurate rendering; dedicated JAMMA PCB systems and PAL mode are unsupported.

Alternatives

For another Neo Geo option, compare NeoCD/SDL if you specifically need a Linux or Windows CD emulator; it is free, but requires an original NeoGeo CD BIOS and restricts source-code reuse and technical knowledge to non-commercial purposes. GnGeo is another free Linux option, but requires SDL 1.2.x, libz, and a NeoGeo BIOS, and its license forbids commercial use of the program as a whole. NeoCDRX is another free option for Linux, macOS, self-hosted, and Windows setups.

Virtual Jaguar is a free, open-source emulator core for a different system and requires a libretro frontend such as RetroArch. NeoDS is free to use for non-commercial purposes. Lynx.emu is a paid, open-source Android app at $2.99, paid once, with ROMs supplied by the user. DOSBox PSP is a free PlayStation Portable port of DOSBox with PSP patches. DREAMNEOCD is a free alternative with non-commercial restrictions on selling and reuse of source code and technical knowledge.

For broader browsing, see Neo Geo Emulators or NES Emulators.

Verdict

Geolith is a strong choice for preservation-minded Neo Geo players who want broad system coverage, fine-grained configuration, and support for unusual input devices without paying for the emulator. Look elsewhere if your games use unsupported cartridge formats, you need PAL or dedicated JAMMA support, or cycle-accurate video timing is essential.