With your PSP sitting on clean 6.60 software, you can now deploy a modern, feature-rich CFW environment. The two primary choices are and LME-2.3 . Both offer flawless homebrew compatibility, but PRO-C2 is highly recommended for its online multiplayer features (PRO Online Client). Installation Steps for 6.60 PRO-C: Download the 6.60 PRO-C2 custom firmware package.
Modern Sony updates (like 6.60) often refuse to execute if they detect older M33 code directly. The safest path is to install an intermediate custom firmware baseline like 5.00 M33-6 or 5.50 GEN-D3, or utilize a tool called . Using Hellcat's Recovery Flasher to reach 5.00 M33: psp 352 m33 upgrade to 660 portable