
Originally Posted by
IndianCheese
I have. Seems too random. I could have thought of that. I pretty much know as much as possible about the PSP without being a coder. My idea for a downgrader is this:
You know how iR Shell lets you do a "system pause" when playing a UMD game or homebrew by pressing L+SELECT while in-game? Remember that. Now think about this: The PSP will not boot updates that are modified. The keyword there? Boot. You would need two memory sticks or a memory stick reader for your computer. You would also need a copy of the 2.70 update and a copy of the 2.70 update with the DATA.PSAR from the 1.50 update. Run a program like iR Shell. Through that, run the 2.70 update. When you get to the "Do not remove mem stick blah blah blah" screen, do a system pause (because the update detects when the Memory Stick is removed if it is free to detect. But if it is frozen by a program (iR Shell), it will not.) Insert a memory stick with the 2.70 update that has the DATA.PSAR from the 1.50 update AND iR Shell. Unfreeze the PSP. The screen will be where it was left, but now, the PSP will continue reading from ms0:\PSP\GAME\UPDATE\EBOOT.PBP\DATA.PSAR, which is the 1.50 update file. The PSP will think it is installing 2.70, but is reading from DATA.PSAR of 1.50, and installing 1.50 files. The PSP will perform a checksum of the files at the end of the update and detect that they are not 2.70 files. It will give an error, ask to reset settings (because they contain setting data from the version you were at for features not available in 1.50), and be downgraded.
The only problem is that PSPs that need downgraded cannot run homebrew (iR Shell), and if you can run homebrew, there is no reason to downgrade. Just a logic issue I thought I would bring up.
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