If you have a collection of ISOs, converting to CHD is safe, reversible, and recommended.
Tools needed: chdman (comes with MAME or standalone from the MAME development tools).
Basic command (Windows/Linux/macOS):
chdman createcd -i "game.iso" -o "game.chd"
For BIN/CUE (better for rare PS2 discs with CD audio):
chdman createcd -i "game.cue" -o "game.chd"
Batch conversion (Windows PowerShell):
Get-ChildItem -Recurse -Filter *.iso | ForEach-Object
.\chdman createcd -i $_.FullName -o "$($_.DirectoryName)\$($_.BaseName).chd"
Expect ~3–5 minutes per DVD game on a modern CPU.
No format is perfect. Before you convert your entire library, note:
Even with "top" ROMs, issues happen. Here is the fix.
Problem: PCSX2 says "No disc present" but the file is right there.
Solution: Your CHD is corrupt. Use chdman verify to check it. You likely need to re-download. ps2 chd roms top
Problem: The game runs slower than the ISO version. Solution: This is a myth on modern hardware. If you have a CPU older than 2015 (Intel 3rd gen or older), decompressing CHD in real-time might slow you down. For everyone else, CHD is faster because it reduces the PCIe bandwidth load.
Problem: My save states aren't working. Solution: Save states are finicky with CHD files if you change emulator versions. Always use "In-game saving" (Memory Card) for CHD files, not save states.
Problem: The audio crackles. Solution: This is usually an Emulation setting (SPU2-X), not the CHD file. Set Async Mix to 10ms.
CHD was originally developed for MAME (arcade emulation) but has been adopted by the PS2 community because it solves every issue inherent to ISOs. If you have a collection of ISOs, converting
1. Lossless Compression The biggest selling point is that CHD compresses the game data without losing a single byte of game data. It removes the "padding" (dummy data developers used to push data to the outer rim of the DVD for faster loading) and compresses the rest.
2. "Load and Play" Convenience In the past, compressed formats (like CSO or GZ) often required patching or caused stability issues. CHD is different.
3. Hardware Benefits If you prefer playing on original hardware using a hard drive (HDD) or an ODE (Optical Drive Emulator like the HDDOSD or PS2 OPL), CHD is a game-changer.