If you are running PPSSPP on an Android phone, a Steam Deck, a Raspberry Pi, or a modded PS Vita, here is why compression is non-negotiable:
While compression is generally beneficial, it requires the PSP or emulator to "decompress" the data in real-time while you play. psp games iso compressed
: If compressing your own, stick to Level 9 for maximum space, but drop to Level 1-3 if you notice the game lagging. PSP ISO: Highly Compressed Downloads Guide - Ftp If you are running PPSSPP on an Android
: To run these files, your PSP must be running CFW (like PRO or ME). Once installed, both .ISO and .CSO files simply go into the ISO folder at the root of your memory card. a Steam Deck