In the early days of arcade emulation (the late 1990s), preservationists faced a problem. MAME was excellent at running classic games from the "Golden Age" of arcades—titles like Pac-Man , Donkey Kong , and Street Fighter II . These games were stored on chips called ROMs (Read-Only Memory). They were relatively small, usually just a few megabytes or even kilobytes in size.
: The format allows MAME to read the disk data exactly as the original hardware would, while preventing accidental corruption by keeping the "image" separate from the machine's BIOS or ROM files. Common Arcade Hardware Using CHDs
In the world of (Multiple Arcade Machine Emulator) and retro gaming, the term CHD stands for Compressed Hunks of Data . It is a specialized file format designed specifically to handle large data storage media from arcade machines and consoles, such as hard drives, CD-ROMs, and LaserDiscs. Why MAME CHDs Are Necessary mame chd
: CHD files should be placed in a specific directory. MAME will look for CHD files in its harddisk directory by default. You can organize your CHDs in subdirectories within the harddisk folder, but make sure MAME knows where to find them (more on this in the MAME configuration).
Unlike raw binary dumps (ISO, BIN, IMG), CHD files: In the early days of arcade emulation (the
: Use chdman verify to check if your file is corrupted.
| Code | Algorithm | Use case | |------|-----------|----------| | zlib | Deflate | General data | | flac | FLAC | CD audio sectors | | lzma | LZMA | Best ratio, slower | | huff | Huffman | Rare | | cdzl | CDZL (custom) | CD-ROM data + subchannel | They were relatively small, usually just a few
However, as the 1990s progressed, arcade hardware evolved. Companies like SEGA, Namco, and Konami moved away from simple circuit boards. They started building arcade machines that functioned more like specialized computers. They used hard drives, CD-ROMs, and DVD-ROMs to store massive amounts of data (full-motion video, high-fidelity audio, and complex 3D models).