Slow Internet: Smaller files are easier to download on unstable or capped connections.
CSO Files: This is a compressed ISO. It uses a compression algorithm to reduce the file size (often down to 1.0 GB or 1.2 GB) while remaining playable directly by most emulators and Custom Firmware (CFW).
A standard PSP game is typically saved in an format, which is an exact sector-by-sector copy of the original UMD disc. The original ISO file for Crisis Core takes up roughly 1.0 GB to 1.2 GB of data.
The original retail game size on a UMD (Universal Media Disc) is approximately . "Highly compressed" versions often found online (typically in .CSO or .ISO formats) reduce this size by compressing audio and video files. Original Size: ~1.6 GB.
provides the highest compression but may cause slight stuttering in FMVs (Full Motion Videos) during gameplay on older PSP hardware. : Load your file, select Compress ISO -> CSO , and run the conversion. You can typically save of the original space. Performance & Stability Considerations
Here is a guide on how to do it, using a popular tool called :
These combined factors have created a massive online demand for to save bandwidth and storage.