Item description:

Homebrew coders' Davee and some1 have teamed up to release a new version of their "multi-firmware downgrader" project, which now allows PSP 3000 09g users to downgrade to firmware 6.20.
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So what does this app exactly do? Well, according to Davee, the downgrader will allow "users who are incontent with their firmware to downgrade to 6.20 using the Sony Updater." As he explains on his blog:"As an ongoing project, me and some1 have been enhancing this downgrader from birth on the 6.31/6.35 firmwares. This multi-firmware downgrader allows you to install a lower (or higher) firmware without any fuss. No complex flash0 sharing, just running the firmware update. However, there comes restriction with PSP models and compatible firmware. For example, a PSPgo cannot run 1.50 as there are no drivers for the system and the IPL format is incompatible. Much like this, the PSP 3000 09g is unable to install firmwares < 6.30 which removes it's ability to appreciate the flexibility of permanent custom firmware."This is no longer the case."It started off with rumours of 09g systems being ???converted??? to 04g systems with some sort of Sony equipment. I explored the firmware comparing 04g and 09g and there is little difference between the modules, so I looked into what makes a 04g and 09g different. I got various testers (named below) to give me information on their IDStorage and internal system data (baryon/tachyon). From this I can conclude that the only (effective) difference between a 04g and 09g is:

Idstorage Certificates
Baryon Version

"Nothing more." Changelog:

Added support for 09g units to 6.20

Developer's note:
How do I use it?

Copy the "PSP" folder to your PSP. The downgrader is "signed" and can be launched from OFW XMB. You need to copy the 6.20 update to PSP/GAME/UPDATE/EBOOT.PBP and for PSPgo it must be the eflash it is placed on. After setup run the downgrader and follow the onscreen instructions.

What does it technically do?

6.20-6.35: It uses the utility/power exploit to gain kernel access and reboots into the updater with a special PRX running. This PRX uses the pspdecrypt functionality to decrypt the updater PRX when needed. This allows the updater to boot in the newer firmwares.
6.38/6.39: It uses my http_storage exploit to gain kernel access.� Basically, http_storage has a vulnerability in it, where I can write -1 to anywhere in memory.
6.60: Uses sceNetMPulldown to gain kernel access.