Game file created by Sega Genesis/Megadrive emulators such as Kega Fusion; contains a freeze state of the ROM (e.g., .32X file) while it is being run in the emulator; allows users to resume games at a specific point in time.
GSX files can also be opened by some versions of Gens, such as Gens/GS.
NOTE: Quick slot save states for Kega Fusion and Gens/GS use the .GS0 - GS9 extensions.