Screenshot published in the CLK project's official README. Image source: CLK project on GitHub.

CLK

MASTER SYSTEM GAME GEAR EMULATOR

CLK

Clock Signal (CLK) is an open-source, multi-system emulator focused on low-latency and signal-accurate reproduction; it includes an emulation of the Sega Master System and supports launching ROMs and disk/tape images with minimal user configuration.

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Screenshot published in the CLK project's official README. Image source: CLK project on GitHub.

master system game gearPRIMARY SYSTEM

History documentedPROJECT BEGAN

Open sourcePROJECT MODEL

WHY IT MATTERS

Why choose CLK for Master System / Game Gear?

CLK emphasises low latency, accurate signal processing (composite/video/audio pipeline emulation) and single-click loading of media. It aims to automatically select and configure the correct machine for a provided ROM/image and to reproduce video/audio artefacts by modelling original outputs rather than applying post-hoc filters.

BEST FOR

Best for

Users who want a low-latency, signal-accurate multi-system emulator with a desktop-style single-click launch workflow and those who prefer building from source for macOS, Linux/BSD (SDL or Qt) or using the official macOS binary where available.

Gameplay from Sonic the Hedgehog on Game Gear.

The people behind CLK

History & status

CLK (Clock Signal) is actively maintained on GitHub as a multi-system emulator containing many 8-bit and early-16/32-bit platforms; the repository includes extensive source, platform bindings and build instructions. The project is hosted and released from its GitHub repository and receives updates (releases and commits) via that upstream. It is offered under an open-source licence and distributed with source and platform-specific builds. The project README and BUILD.md describe the emulator's aims, supported machines (including the Sega Master System) and build targets. Third-party projects and distributions (for example Batocera) have adopted CLK as an available Master System option.

What CLK supports

Sega Master System
Sega Game Gear
Note: verify specific Game Gear coverage for the particular build/target before use
Other multi-system targets are supported by CLK (see project README for full list)

Download and availability

OFFICIAL DOWNLOADS

Get CLK

Official releases and source are available from the project's GitHub releases page; macOS native builds are provided in the repository and there are Snap/packaging options for some Linux targets. Source releases are on GitHub and the BUILD.md documents how to build platform binaries.

Get CLK ↗

DOCUMENTATION

Official documentation

Read the official configuration, compatibility, and troubleshooting material before changing advanced options.

Read official documentation ↗

Broken or missing download? Emulator projects move and official links sometimes change. Please contact Retro Replay so the source can be verified and updated.

CLK setup guide

Setup note: This guide summarises verified, emulator-specific setup and build steps from the project's repository for macOS, SDL (cross-platform) and Qt builds and practical steps to run Master System / Game Gear media. It assumes you will obtain any required original machine ROMs/BIOS separately if needed; these are not included in the project.

Obtain the source or releases: Get the source or prebuilt releases from the official GitHub repository and releases page. Use the Releases page to download official tagged builds where provided, or clone the repository to build from source.
macOS native app (recommended for macOS users): CLK provides a native macOS app built with Metal. Requirements: Metal-capable Mac running macOS 10.13 or later. You can open the Xcode project in OSBindings/Mac and build in Xcode, or run xcodebuild in that directory. To avoid code-signing problems, set CODE_SIGN_IDENTITY to '-' or in Xcode set Signing to 'Sign to Run Locally'. The BUILD.md documents unchecking 'API Validation' for Metal in some Run schemes to avoid crashes on older macOS versions.
SDL build (cross-platform: Linux, BSD, macOS): The SDL target produces a command-line-driven clksignal executable. Prerequisites include SDL2, Zlib and OpenGL (OpenGL 3.2+ at runtime). The BUILD.md shows SCons and CMake build paths. Example CMake (from repo root): cmake -S. -Bbuild -DCLK_UI=SDL -DCMAKE_BUILD_TYPE=Release then cmake –build build [-jN]. With SCons, change into OSBindings/SDL and run scons -jN. The resulting clksignal binary can be copied to /usr/local/bin or run in-place.
Qt build (X11-focussed Unix builds): The Qt app is built with Qt6 (or QMake) and OpenGL. Install Qt6 dev packages (qt6-base-dev, qt6-multimedia-dev) and run cmake with -DCLK_UI=Qt or use qmake inside OSBindings/Qt. Build steps are in BUILD.md and the produced clksignal executable will be in the build subdirectory.
Dependencies and example Debian/Ubuntu packages: BUILD.md includes example apt-get package lines for Ubuntu for SDL and Qt builds; for SDL: install cmake, gcc-10, libsdl2-dev (and zlib/OpenGL/Mesa). For Qt: install qt6-base-dev and qt6-multimedia-dev in addition to cmake and a compiler.
Where to place machine ROMs / BIOS files: Some emulated systems require original machine ROMs. These are not distributed with CLK. When required, place them in /usr/local/share/CLK/ or /usr/share/CLK/ (or the equivalent paths on macOS inside the app bundle if you populate ROMImages before building). The BUILD.md explains the folder structure under the OSBindings/ROMImages area and that you'll be prompted if expected ROMs are missing.
Running media: The SDL/Qt builds offer a clksignal executable that accepts a filename: clksignal file or ./clksignal file. CLK seeks to auto-detect the correct machine and will attempt to run the media with minimal user setup. You can also configure your OS to open supported image/ROM extensions with clksignal for single-click launches.
Practical notes for Master System / Game Gear: CLK lists the Sega Master System among its supported machines in the README. Confirm whether your chosen build includes the specific Master System/Game Gear machine definitions and required ROMs by checking the ROMImages folders in the source or by running clksignal and observing any prompts for machine ROMs. If you need Game Gear-specific functionality, validate it on the build you compiled (behavior may vary between SDL, Qt and macOS builds).

Software reminder: CLK does not include commercial games, firmware, BIOS images or other copyrighted machine ROMs; you must supply any original ROM/BIOS files yourself and place them according to the project's documented layout.