You do not need to risk downloading shady, pre-compressed files from sketchy websites. You can safely compress your own legal backups using a free, lightweight tool called (which comes bundled with MAME). Step-by-Step Guide using CHDMAN:
Developed initially for the MAME arcade emulator, CHD has become the gold standard for PS1 compression. It compresses data and audio tracks into a single file. Most modern emulators can read CHD files directly without extracting them. Ps1 Roms Highly Compressed
Hackers eventually figured out how to convert standard PS1 ISOs into PBP files. PBP natively supports multi-disc games, meaning you can combine a 4-disc game like Final Fantasy IX into one single file. Average Size Reduction: 20% to 40%. You do not need to risk downloading shady,