Installing Custom Firmware on a PSP : 9 Steps - Instructables
NoUMD PSP - GameBrew
Infinity 2.0 released for the PSP, allows for persistent CFW on all models of PSPs on 6.60 and 6.61 | Page 3 | GBAtemp.net - The Independent Video Game Community
How to install a permanent CFW on any PSP without hardmod. | GBAtemp.net - The Independent Video Game Community
Some guidance is needed. I bought a PSP go from eBay has cfw already on it. It's on update 6.20 Pro-B10 : r/psphacks