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How to downgrade PSP firmware?
11-23-2011, 01:07 PM (This post was last modified: 11-23-2011 01:10 PM by mksmns1126.)
Post: #1
How to downgrade PSP firmware?
How to downgrade PSP firmware?

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If you have purchased a PSP running Version 2.0 of the firmware, complete with browser, you can downgrade to Version 1.5 with a few easy, albeit somewhat risky, steps. When you are done, the entire world of homebrew will be open to you.

Fortunately, some industrious hackers discovered a buffer overflow error that occurs when loading an appropriately created image file through the PSP's Photo menu. Then, someone realized that the buffer overflow allowed for a modicum of code to be run. Finally, the pieces fell in place when someone thought to overwrite the PSP's System Information during this error, so that a PSP running Version 2.0 of the firmware would be fooled into thinking that it was running Version 1.0. A simple substitution of a 1 for a 2, and suddenly you are able to run the 1.5 Software Update to replace the Version 2.0 firmware, effectively downgrading your system to a more hacker- and homebrew-friendly version of the firmware.

Keep in mind that working with firmware is always risky. Having the power supply cut in the middle of a regular Sony authorized firmware upgrade could very quickly turn your $250 PSP into a $250 doorstop. Such an error in a normal firmware upgrade, though, would be covered under Sony's warranty. Anything that goes wrong with this hacked downgrade won't be covered, so make sure you follow these steps carefully, and consider yourself warned. Proceed at your own risk. Also, be careful where you grab your copy of the downgrader and the 1.5 updater used in this tips; there have been reports of malicious packages posing as these two items that can actually destroy your PSP.

Everything in the Right Place
Download the MPHDowngrader from either http://www.chez.com/mph/, http://www.psp-hacks.com/downloads/MPHDowngrader.zip, or http://www.alden0186.freeserve.co.uk/MPHDowngrader.zip.
You will also need a copy of the original 1.5 firmware update. I found my copy via Shockzone (http://shockzone.free.fr/PSP/Tool/EBOOT_1.50.zip). Once you have downloaded the necessary files, unzip them. You will find a Read Me file included with the MPH downgrader that you can follow if you don't want to read through this entire tips; however, the Read Me is a little confusing. So unless you are fluent in "I'm a hacker too busy coding to write a Read Me" shorthand, I suggest you read on.

EBOOT.PBP.
Connect your PSP to your computer via USB. On your Memory Stick, create a folder called UPDATE inside /PSP/GAME/ and place the EBOOT.PBP file from the 1.5 update inside this UPDATE folder.

MPHDowngrader pieces.
Drop the overflow.tif file that was included in the MPHDowngrader folder into your /PSP/PHOTO/ folder, as you would with any image that you wanted to view on your PSP.

Put both h.bin and index.dat in the root directory of your Memory Stick (in other words, just drop them straight into the Memory Stick without placing them inside any folders).

Trigger the Overflow
After you have all the files in the right places, disconnect your PSP from your computer and plug it into the AC adapter. Make sure that there is no UMD in your PSP and that you have wallpaper turned off before you begin.

On your PSP, navigate to Photo Memory Stick and hit the X button to start scrolling down through your photos until you reach the overflow.tif picture. You'll know you've hit it when everything freezes and you get a black screen with a bunch of white text output. This may happen before you even see the overflow.tif file name, but if not, simply select the image and hit the X button. The black screen with white text should appear. If your PSP freezes without going to this black text screen, hold the power button up for about 10 seconds until the PSP shuts down, then hit the power button again to start it back up. Repeat this step until you get that black screen.

If the black screen with white text doesn't appear to be showing up for you, try connecting your PSP to your computer again and check at the root level of your Memory Stick for a new file there called index.dat.bak. If that file is there, then the overflow worked, but you just didn't get the lovely black and white screen. Go ahead to the next step.

Don't panic. The frozen black screen with white text is what was supposed to happen. Hold the power button for about 10 seconds until the PSP powers off. Hit the power button again. Your PSP will start up, and if you navigate to your System Information (Settings System Settings, hit the X button, then scroll down to System Information and hit the X button again), you'll discover that your PSP thinks it is running Version 1.0 of the firmware. It isn't, and you cannot run homebrew (yet). The important thing is that the PSP thinks it is running 1.0, which means that it will allow you to run the 1.5 Firmware Update over your 2.0 firmware.

Run the 1.5 Updater
Navigate to Game Memory Stick, hit the X button, and navigate to the 1.5 Updater. Make sure that you have your PSP plugged in, or the upgrade won't work. Hit the X button and update as you normally would. At the end of the upgrade, the update will freeze at 99% completion, and you will receive an error saying that the upgrade failed and to contact Sony. Don't panic, and don't contact Sony. Ignore this warning and again force your PSP to power off and reboot.

After the PSP reboots, you will receive an error screen that is scary and confusing because it is in multiple languages. Don't panic. Find the language you can understand and read the corresponding line. It notes that your preferences are fragged and that you need only hit the O button to restore some default-ish settings. Hit the O button.

Some hackers have claimed that unplugging the AC adapter and pulling the battery when this warning appeared resulted in them having a PSP running 1.5 firmware capable of running homebrew, but retaining the 2.0 browser. However, you should never leave the PSP plugged in when you remove the battery (I fried one PSP this way), and a few people have reported that following those directions turned their PSPs swiftly into nonfunctional bricks.

Set up Your PSP
The PSP will start back up and you will go through the initial setup like the day you first bought your PSP. Do so, and then go to the system info pane again, where you will see that you are rocking Version 1.5 of the firmware (Settings System Settings, hit the X button, then scroll down to System Information and hit the X button again). Run homebrew at will .

If you really love your PSP's browser and don't really want to give it up, don't worry. Simply back up all the browser-related files from your Memory Stick before downgrading. I ran through this entire procedure, downloaded the 2.0 update and installed that again, and then went through the entire procedure again. It worked like a charm. It's a little time-consuming, but you can have the best of both worlds. Have fun! Just make sure that you don't install any firmware past 2.0, as I am sure Sony intends to plug this hole again as soon as possible. Even if they do, though, I'm confident that the PSP hackers out there will find a way around it.

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