Complete tut on how to downgrade your 2.6

[Watchmeexplode5]

2/3 psp will brick when you do this.
This was taken from http://forums.qj.net/showthread.php?t=56408
To be used at your own risk. It is an UNTESTED software.

Users with TA-082 psp's shouldn try this. Also, it may be better that at the beginning, only users with a 2.50/2.60 NOT from factory (they updated from a below firmware) try this.

Download link:

PLEASE TRY THIS AT YOUR OWN RISK, WE HAVE HAD REPORTS OF BRICKING FROM THIS EARLY ON
Password: I_Use_This_at_My_Own_Risk

I copy and paste the readme here. Read it carefully.

------------------------------------------
Downgrader Test for 2.50/2.60 by Dark_AleX

This is an *experimental* downgrader for 2.50/2.60

Experimental means here that it has not been tested on a real device, althought it has a theoretical base that it could work.

This software is free and untested, and i'm not responsable if it causes damages to your psp.
If you use this software, you agree that you are using this program at your own risk and that you won't blame the author for that.

"Someone told me that a downgrader for 2.50/2.60 was impossible. How does this work?"

This one uses another more risked technique (and i repeat: untested) than the mph downgrader.
It uses some sony libraries found in the 1.50 updater to perform the most critical steps, the logical format of the flash, and the ipl writing. See technical details for more info about how it works.

This software requires that someone with a 1.50 runs a little program and send you the output so you can init the downdate process. (by legal reasons i cannot provide those files directly, that's why this is needed).
The 1.50 program is TOTALLY safe, it only dumps the flash of a 1.50 user and it also extracts some special prx's found in the 1.50 updater.

Instruction for the 1.50 user
-----------------------------

1) Copy the folders downhelper and downhelper% from the folder 1.50 HELPER folder to /PSP/GAME/ in your memstick.

2) Obtain the 1.50 updater and put it in /PSP/GAME/UPDATE in your memstick.

Some download links for it:

http://www.psphacks.net/files/PSPFirmwares/1.5/

http://dl.qj.net/PSP-Firmware-1.50-File-(EBOOT)-North-America-PSP/pg/12/fid/163/catid/163

3) Init the downhelper program.
It will dump your flash and some files from the updater eboot to the memstick.

4) After that, the program will exit. You can now delete the updater from /PSP/GAME/UPDATE

5) You'll notice that you have a new folder in the root of your memstick called "DOWNDATER".
That's the folder you'll have to send to a 2.50/2.60 to let him test the downgrade.



Instructions for the 2.50/2.60 user
-----------------------------------

1) Copy the folder the DOWNGRADER/2.50/DOWNDATERTEST if you have 2.50
or DOWNGRADER/2.60/DOWNDATERTEST if you have 2.60 to /PSP/GAME/ in your memstick

2) Wait someone with 1.50 to pass you a folder called DOWNDATER and copy it to the root of your memstick.

3) Init gta and the eLoader

4) In the eLoader menu, choose the downdater test. WARNING: the program won't output any display and any warnings, it will init the downgrader process inmediatelly.

5) You'll see the your memstick flashing. That means that your psp is being flashed from the memstick.
You won't see any type of output in the screen (this is for safety). When the memstick finishes of flashing, WAIT at least a minute, and then reinit your psp by holding the power button.

6) That's all. If all went right, you'll have 1.50. If it went less good, you'll still have 2.50/2.60. If all went wrong, you'll have a bricked psp(except in the case you have the modchip) Remember that you have accepted that risk.


Technical details
------------------

This program performs the following operations.

- It loads the ipl_update.prx and lflash_fatfmt.prx from the 1.50 updater.

- It performs a logical format of the flash0 partition using the function
sceLflashFatfmtStartFatfm t found in the lflash_fatfmt.prx

- It writes a dump of the 1.50 flash0 to the flash0.

- It writes the Initial Program Loader (Ipl) using the functions sceIplUpdateClearIpl and sceIplUpdateSetIpl from the ipl_update.prx module. The ipl is embedded in that module.

Hope this helps. Rember that this has a great chance of bricking you psp. I have bought the mod chip because I don't want to take the risk and I also want to be able to switch fw in a snap.

Edit:
Srry for posting this when there was already a link in the kernal exploit.

[bridger69]

seems really risky, i wouldn't recommend trying this only if you desperately want homebrew on ur psp

[Watchmeexplode5]

Ya. This is incredibly risky. I haven't seen real proof of it working. Its just a concept. Some people said it worked. Mosted bricked their psp. If you need the Homebrew that much then get U.P.