.SFC

Introduction

A .sfc file is a copy of the ROM in a cartridge for the Super Nintendo Entertainment System, known in Japan as the Super Famicom, for playing in an emulator. The older extension .smc comes from the Super Magicom, a 1990s copier that loaded games from floppy disk. Copiers like it put a 512-byte header of their own in front of the ROM, so .smc files often carry one, while .sfc files are normally the plain ROM.

Structure

The ROM holds an internal header written by the game’s developer. Where it sits depends on how the cartridge maps its ROM into the console’s memory: at 0x7FC0 in the file for LoROM games and 0xFFC0 for HiROM games. Emulators find it by checking both places for a header that makes sense, and detect a copier header when the file size divided by 1024 leaves 512.

The checksum is the 16-bit sum of every byte in the ROM, and the complement is that value with all its bits flipped, so the two always add up to 0xFFFF.

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