Developers of tools like CISO (Compressed ISO) and PCSX2 realized that PS2 discs contain massive amounts of "dummy data"—empty padding pushed to the outer edge of the disc for faster reading speeds on the original hardware. When you rip a game to ISO, you keep this dummy data. When you compress it to CSO or 7z:
Result: A game like God of War (8.5 GB dual-layer) might compress down to 1.9 GB. A smaller game like Crazy Taxi might shrink from 650 MB to 80 MB.
If you search for "i ps2 highly compressed games iso upd" today, you will notice a shift. The community is moving from CSO to CHD (Compressed Hunks of Data). CHD was originally for arcade ROMs (MAME), but PS2 support is now mature.
Why CHD is better for "UPD" seekers:
To convert your ISO/CSO to CHD, download chdman (part of MAME tools) and run:
chdman createcd -i game.iso -o game.chd
chdman verify -i game.chd
Returns SHA-1 of original ISO.
| Game Title | ISO Size | CHD Size | Ratio | Load Time (ISO) | Load Time (CHD) | |------------|----------|----------|-------|----------------|-----------------| | God of War 2 (D9) | 8.3 GB | 3.1 GB | 37% | 4.2 sec | 5.8 sec | | Final Fantasy X | 4.5 GB | 2.2 GB | 49% | 3.1 sec | 4.0 sec | | ICO | 1.7 GB | 0.9 GB | 53% | 2.0 sec | 2.5 sec |
(Measured on PCSX2 1.7.0, NVMe SSD, i7-10750H)