maxcso -o game.cso game.iso
When building your archive, understanding the balance between raw performance and storage efficiency is crucial. ISO (Uncompressed) CSO (Compressed) Large (100% of original data) Small (often 30% to 60% reduction) Load Times Faster on original PSP hardware Marginally slower on original hardware Emulator Performance Flawless on modern PCs/smartphones Compatibility Requires Custom Firmware (CFW) or Emulator The Compression Levels CSO files support nine levels of compression (1 to 9):
Maxcso is a modern, open-source command-line compression tool optimized for speed. It utilizes multiple CPU cores to compress ISOs into CSOs much faster than legacy tools. It also supports the newer and ZSO formats, making it a favorite for power users managing large libraries. Ciso Plus / YACC (Yet Another CSO Compressor) cso psp archive
If you play PSP games on modern hardware using the emulator (on PC, Android, iOS, or Steam Deck), CSOs are fully supported. Modern processors handle on-the-fly decompression effortlessly, meaning you get all the space-saving benefits of CSOs with absolutely zero performance penalties. Understanding Compression Levels
When creating a CSO archive, you choose a compression level ranging from . maxcso -o game
Because the PSP's CPU must unpack the data during gameplay, initial loading screens and transitions might take a few seconds longer compared to playing an uncompressed ISO.
Modern, fast command-line tools available for Windows, Mac, and Linux that support multi-threaded compression. Step-by-Step Conversion Guide (Using UMDGen) Download and launch UMDGen . It also supports the newer and ZSO formats,
Games that constantly stream data from the disc—such as Grand Theft Auto: Liberty City Stories , Midnight Club 3 , or God of War: Ghost of Sparta —may stutter or experience audio dropouts when compressed too tightly as CSOs on real PSP hardware. It is best to keep these specific titles as uncompressed ISOs.
Move the resulting .cso file into the ISO folder on your PSP's memory card. Best Practices for Managing Your Archive
You can find it on GitHub and run it from the command line. A typical command looks like this: