ISO vs CSO
ISO Versus CSO
PSP game backups come in two main formats. Both go in the ISO folder and both launch the same way, but they handle storage differently.
ISO: The Raw Image
An ISO is an exact, uncompressed copy of the UMD's data. It is the simplest format, loads quickly, and has the broadest compatibility because nothing is altered. The trade-off is size: an ISO uses the full space of the original disc.
CSO: The Compressed Image
A CSO is a compressed ISO. Software shrinks the image so it takes less room on the Memory Stick, which matters when cards are small or games are large. The PSP decompresses it on the fly during play.
The Compression Trade-off
Higher compression saves more space but asks the CPU to do more work while loading, which can slightly increase load times or stutter in demanding games.
| Format | Size | Speed |
|---|---|---|
| ISO | Full | Fastest, most compatible |
| CSO | Smaller | Slight CPU overhead |
Which to Choose
- Use ISO when you have plenty of space and want maximum compatibility.
- Use CSO to fit more games on a limited card.
- Try a moderate compression level for a good balance.
A small number of games are sensitive to high compression. If one misbehaves, store it as a plain ISO instead.