Highly compressed .cso files can sometimes cause stuttering or infinite loading loops on older PSP memory sticks due to read-speed bottlenecks. If you experience lag during intense gunfights, convert the file back to an uncompressed .iso format.
For Fireteam Bravo 3, a standard ISO takes up roughly 1.2 GB of space. A highly compressed version can reduce this footprint down to 400 MB to 600 MB. This compression allows players to store more games on limited Memory Stick duos or mobile device storage when using emulators. Gameplay and Features of Fireteam Bravo 3 socom fireteam bravo 3 psp highly compressed
SOCOM: U.S. Navy SEALs Fireteam Bravo 3 PSP Highly Compressed Guide Highly compressed
A highly compressed PSP game is an ISO image file that has been processed using advanced compression algorithms (such as .CSO formatting, .RAR , or .7z archiving). A highly compressed version can reduce this footprint