A CSO (Compressed ISO) is a standard PSP ISO file run through a compression algorithm (usually LZMA or ZLIB). Think of it as a .zip file the PSP can read on the fly.
CSO files are game backups. You should only create or download CSO files for games you physically own (original UMD discs). Downloading copyrighted games from the internet without owning them is piracy and violates the law in most countries. juegos cso para psp
If you have a large ISO file, you can compress it into a CSO to save space using a PC program. A CSO (Compressed ISO) is a standard PSP
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