What is saturn_mister?

Saturn_MiSTer is a hardware core that recreates the Sega Saturn game console on MiSTer, a device that uses reprogrammable chips called FPGAs to rebuild classic gaming hardware in a way that behaves like the real machine rather than software emulating it. This particular repository is a fork of the original Saturn core that adds support for RetroAchievements, a service that tracks in game accomplishments similar to trophies or achievements on modern consoles. To get achievement tracking working, the core needs to be paired with a special RetroAchievements-enabled version of Main_MiSTer, the software that runs the MiSTer device itself. The stock version still runs games fine, it just will not track achievements. The core already stores the console's working memory inside the board's DDR3 memory chips, so the RetroAchievements side can read game memory directly without needing a separate copy. The only change made to the hardware description is a small addition to an existing memory arbiter that writes a frame counter once per video frame, timed to match the exact moment other Saturn emulators check for achievement progress, so the main game logic itself is never touched or slowed down. The fork is built on a specific point in the original project's history and includes a handful of upstream bug fixes for graphics corruption in certain games, along with a fix for controller and LED behavior. One larger accuracy improvement from upstream was deliberately left out because it would make the core too large to fit on the target chip. Setting it up involves installing the RetroAchievements enabled Main_MiSTer, creating a small configuration file with your RetroAchievements username and password, then loading the core and mounting a Saturn CD image. Achievement tracking then starts automatically once the game is recognized, no Saturn specific setup is required. The hardware requirements are a primary 128 megabyte SDRAM module and a second SDRAM module of any size, with two modules recommended for better game compatibility. The README does not state a license.