Fit more PSP ISOs on your memory stick using CSO

[Harrison]

As some of you are just starting with the PSP and custom firmware, I thought I would give a little tip regarding game ISOs.

There is a format called CSO which is a compressed version of an ISO image. Turning a PSP game ISO into a CSO can reduce the files by quite a bit and therefore give you more room to fit more games on your memory stick at once. All custom firmwares support this format so it is worth using to give you more space on your MS.

As an example here are three games I converted recently and this is the results:

Final Fantasy 1. ISO = 193,472 KB, CSO = 150,727 KB.
Final Fantasy 2. ISO = 280.608 KB, CSO = 232,454 KB.
Dungeon Siege. ISO = 881,120 KB, CSO = 729,345 KB.

So even quite small ISOs get reduced by quite a bit. Over 40MB. And the larger DS ISO by over 150MB which is a big reduction.

There are quite a few different CSO compression utilities available, but I used one called PSP ISO Compressor. This is simple to use in Windows and just requires you to select: CSO as the compressor, the source game ISO, the destination for the CSO to be created, and the compression ratio. Very easy and most games I convert to CSO files work perfectly.

I've included PSP ISO compressor as an attachment. You can also find other CSO compressors and many other utilities at PSP Hacks.

notes:
You many notice some games will load slightly slower than usual once converted into a CSO. This is normal as the file is compressed, so the PSP has to uncompress it as it loads.

Some games may not load once converted to a CSO. If this happens try making the CSO again, but with less compression. The problem is often due to some games needing to read data at a set rate and the CSO is too compressed to allow this.