If you have a large library, you can convert all your games at once using a simple command-line script.
For PSX games, a standard .bin file (raw disc image) is exactly 2352 bytes per sector, regardless of whether the sector contained actual game data or blank padding. A .chd file analyzes these hunks, removes redundant padding, and compresses the actual data. chd psx roms
If you are setting up a personal emulation station, converting your PSX library to is a one-time investment that saves gigabytes of space, organizes your files (one file per game), and works flawlessly on modern emulators. If you have a large library, you can