For decades, emulating the Sega Saturn was considered the "final frontier" of console emulation. Its complex dual-CPU architecture made game compatibility a nightmare. While emulators like Mednafen, Beetle Saturn, and Yaba Sanshiro have since matured, a secondary battle has emerged for retro gamers: storage space.
A single Sega Saturn game can be a massive 650MB ISO. When you start collecting classics like Panzer Dragoon Saga (3 discs), Deep Fear, or Guardian Heroes, your hard drive fills up fast.
Enter the CHD (Compressed Hunks of Data) format. Originally designed for arcade games in MAME, CHD has become the gold standard for compressing Sega Saturn ROMs. sega saturn roms chd
In this guide, we will explain what CHD files are, why they are better than BIN/CUE or ISO, how to use them on modern emulators and handhelds (like the Steam Deck or Retroid Pocket), and how to convert your existing library.
CHD (Compressed Hunks of Data) files are a container format used to store disc images (including Sega Saturn discs) in a compressed, lossless form commonly used by emulation software such as MAME and other retro emulators. Sega Saturn ROMs can be distributed either as single-bin/cue disc images or converted into CHD to save space and improve performance in some emulators. The Ultimate Guide to Sega Saturn ROMs in
To understand the significance of CHD, one must first appreciate the unique obstacles of Saturn disc images. Unlike cartridge-based systems (like the SNES or Genesis), the Saturn used CD-ROMs. Early ripping methods produced either ISO+WAV+CUE files (uncompressed but messy, often losing audio gaps) or BIN/CUE pairs, which were accurate but enormous. A single Saturn game, such as Panzer Dragoon Saga (which spanned four discs), could consume over 2 GB of raw BIN/CUE storage. Furthermore, many Saturn games contained large amounts of dummy data—intentionally placed filler to push game data to the faster-read outer edges of the disc. Preserving a full library of 1,200+ titles in raw format would require terabytes of space, making it impractical for average users or smaller archival projects.
Emulation also suffered. Popular emulators like Mednafen (later integrated into RetroArch as the Beetle Saturn core) required specific, lossless disc images to function correctly. Missing subchannel data (Q and R-W channels) would break games with copy protection, such as Guardian Heroes or Radiant Silvergun. The result was a fragmented landscape: either suffer massive file sizes or risk corrupting game audio and functionality. Using CHD images with Saturn emulators
Why CHD is used for Saturn:
Previously known as Yabause (but vastly improved). Kronos has better performance on low-end PCs than Mednafen.
Original Sega Saturn games were pressed on CD-ROMs, typically holding 300–650 MB of data. When ripping these discs to a computer, raw formats like BIN/CUE (binary image with cue sheet) or ISO were standard. However, a single Saturn game in BIN/CUE often consumes 500–700 MB. With a full library of over 1,000 titles, storage requirements can exceed 500 GB. Moreover, BIN/CUE files are inefficient for archiving because they do not compress empty sectors or redundant data.