To achieve these small file sizes, users typically utilize tools like YACC (Yet Another CSO Compressor) or .
can be shrunk, they often still exceed 150MB even in .CSO format.
The first question a modern gamer might ask is: How is this possible? The answer lies in the difference between commercial UMD (Universal Media Disc) dumps and community-driven compression. A standard PSP game, such as Lumines or Patapon , might natively occupy 300–500 MB due to FMV (full-motion video) cutscenes, redundant file structures, or “dummy data” inserted to speed up UMD seek times. Compression tools like UMDGen, CISO, and CSO compression formats strip these elements. A “rip” might remove 4:3 intro videos, convert audio from PCM to lower-bitrate MP3, or delete multiplayer assets. The result? A game like Puzzle Quest: Challenge of the Warlords —originally 110 MB—can be crushed to just 55 MB without losing a single turn of its addictive match-3 RPG combat.