| Feature | CDI (DiscJuggler) | GDI (Raw Dump) | CHD (Compressed Hunks of Data) | | :--- | :--- | :--- | :--- | | | Lossy (Missing data) | Lossless (1:1 copy) | Lossless (Mathematically perfect) | | File Size | ~300MB - 700MB | ~800MB - 1.2GB | ~400MB - 800MB | | Compatibility | Burn to CD-R / Old emulators | Modern emulators (Redream, Flycast) | Modern emulators + MAME | | Best Use Case | Playing on original hardware (via MIL-CD exploit) | Digital preservation / High-end emulation | Archiving / Hard drive storage |
These "homebrew" GDIs run perfectly on GDEMU hardware and emulators, effectively adding new "lost" games to the Dreamcast library 20 years after the console died. If you love the Sega Dreamcast, you owe it to yourself to abandon the compressed, choppy CDI files of the early 2000s. The Dreamcast ROM GDI format represents the highest fidelity available to emulation fans. dreamcast roms gdi
Enter (Compressed Hunks of Data), a format developed by the MAME team. CHD compresses GDI files without losing a single bit of data. It uses hunk-level compression, often shrinking a 1.1GB GDI file down to 400MB—rivalling the size of CDIs but with perfect quality. | Feature | CDI (DiscJuggler) | GDI (Raw