Updating The PSP System Software to 6.60 / 6.61 - pspunk
The last missing piece: Permanent 6.60 CFWs for all PSPs in near future!? - Wololo.net
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Found my old 1000, should I upgrade from 6.60 PRO-C? : r/psphacks
PSP Custom Firmware 6.00-6.61
How do I update my PSP version 5.50 with Custom Firmware to 6.60 or 6.61 ? im really bad at stuff like this so i need help : r/PSP
4 Ways to Upgrade Your PSP Firmware - wikiHow
Infinity 2.0 released for the PSP, allows for persistent CFW on all models of PSPs on 6.60 and 6.61 | GBAtemp.net - The Independent Video Game Community
PSP Slim (6.60 PRO-C) with UK plug, Video Gaming, Video Game Consoles, PlayStation on Carousell
How To Upgrade to PSP 6.60 PRO-C2 Custom Firmware [2021] - YouTube