Open the root directory of your memory stick. If you do not see a folder named ISO (all caps), create one.
Highly compressed games run identical to their full-sized counterparts because the compression primarily targets empty padding data or duplicates within the game files. However, if you experience lagging or stuttering during chaotic firefights, use these settings to optimize your gameplay: metal slug psp iso highly compressed
An is an uncompressed or raw copy of the game disc. A CSO (Compressed ISO) is a natively compressed PSP format. PPSSPP can read .cso files directly without needing to extract them further, saving permanent storage space on your device. Can I play multiplayer on a compressed version? Open the root directory of your memory stick