The
"extensions" don't really mean anything, they're just descriptive, the file itself is a simple binary file. Extensions exist solely for the sake of identifying a file type, they serve no other function. They're self-explainatory, here's a quick run-down:
- .SMD - Sega Mega Drive (PAL or NTSC-J) ROM dump
- .GEN - Sega Genesis (NTSC-U) ROM dump
- .SMS - Sega Master System (Any Region) ROM dump
- .32x - Sega 32X (Any Region) ROM dump
- .ROM - Generic ROM file (Could be anything)
- .BIN - Generic binary (Could be anything)
- .ISO - Disc Image file (Sega CD, Sega Saturn or Dreamcast, Any Region)
- .BIN + .CUE - Disc Image file pair (See above)
- .CDI - DiscJuggler Disc Image (See above, most commonly Sega Saturn, Any Region)
- .GDI - GD-ROM Image file (Dreamcast, Complete GD-ROM rip, Any Region)
I believe that's all of them.