A CSO file can be 30% to 70% smaller than the original ISO. For example, a game like Grand Theft Auto: Vice City Stories might be 1.5GB as an ISO but only 600MB–800MB as a CSO.
: While most games run perfectly as CSOs, a few titles may lag or crash, in which case the standard ISO format is preferred. 2. How to Use CSO Files on Hardware To play CSO games on an actual PSP, the device must have Custom Firmware (CFW) installed. cso psp games download