I wrote this because there are very few useful tutorials that guide you step by step on how to downgrade.
There is a tutorial already on romulation on how to upgrade your PSP to custom firmware, but you need a very early firmware to do so.Things you will need:
PSP
Pandora's Battery ($10.50 at dealextreme)
Memory stick >64 MB
PSP grader (I used the old v0.2)
*150.pbp (1.50 kernel for 3.90 M33-*)
*390.pbp (3.90 M33-*)*No matter which versions of 3.90 M33 you get, make sure they match. It also doesn't matter what firmware you get since PSP grader will "patch" them onto your memory stick. So you can have 3.90 M33, 3.90 M33-2, and the 1.50 kernels respectively and PSP grader will put those onto the memory stick. (although you should look for the M33-3 version since it is the best. As of writing this, 4.01 still has a few compatibility issues, so it is recommended you do not upgrade to 4.01)First, you will need to make a magic memory stick.Using PSP grader and the two firmware files (150 and 390):
1. Connect your memory card to your computer via your PSP or an adapter.
2. Install PSP grader.
3. Run PSP grader
4. Put the 150 and the 390 pbp files in their respective fields.
5. Point the drive of your PSP memory card in the last field.
6. Hit start.
Magic memory stick is done!Now, you will need a pandora's battery.It is easier to just buy one than to make one.Now assuming that you have both the pandora's battery and the newly made magic memory stick in hand, you are ready to downgrade your PSP.1. Put both the magic memory stick and the pandora's battery in the PSP. MAKE SURE THE BATTERY IS SECURE, DOESN'T FALL OUT OF PLACE!
2. The PSP will startup automatically.
3a. For newer versions of the PSP grader, the menu will pop up automatically.
3b. For older versions, turn off the PSP, restart holding L to get to the menu.
4. When the black menu pops up, hit X to downgrade. DO NOT TOUCH THE PSP!!!
5. After it is completely installed, flashed, etc. press X again to complete the install and the PSP will shut off.
6. Switch out the pandora's battery and put in the regular battery.
7a. For fat PSPs only: run the 1.50 kernel, install, and shut off.
7b. Go to step 8.
8. For both slim and fat PSPs: boot up the PSP this time holding R.
9. Go to Configurations and set 'Hide Corrupt Icons' to 'enable.'
10. Go to Configurations, turn off the UMD drive and it will switch to the M33 driver - NO UMD.
11. Now go back and go to registry hacks.
12. Enable Flash and WMA.
13. Go back and exit.*Optional: If you plan on playing homebrew, set the kernel to 1.50 through the service options like steps 9-13.You are done.
Reformat your memory card (through the PSP) to make it a regular memory card.If you want to upgrade your newly upgraded 3.90 M33-3 firmware to the 4.01 version, you will need to get the 4.01 custom firmware and the 1.50 kernel specifically for 4.01. Again, for PSP-1000s, you will have to run the 1.50 kernel installer.FAQ:
Q: If I have a slim PSP, do I need to have the 150.pbp.
A: Yes, PSP grader integrates that into the magic memory stick for flashing purposes, even though you don't do the extra step at the end.Q: Will the 32 MB memory stick work as a magic memory stick?
A: No since it can't even hold the two files, 150.pbp and 390.pbp, or the rest of the files.Q: How many MB does the magic memory stick take up?
A: 41.6 MB, so the smallest card you can use is 64 MB.Q: If I use my memory stick to make the magic memory stick, will I be able to use it as a regular one?
A: Yes, just format the stick using the PSP menu so it puts in all of the required folders and such (like the custom firmware ones).Q: When I put in the pandora's battery and the magic memory stick. it boots up normally. How do I get it to boot with the pandora?
A: You have the older version of PSP grader and you need to hold L when starting up your PSP.Q: You said to disable the UMD drive and enable the M33 driver. Does the UMD still function?
A: Yes it does, you just need the M33 driver enabled to play
A: It is needed to play homebrew/homebrew games.Q: This tutorial only gets me 3.90 M33-3. Should I upgrade to 5.XX?
A: Yes. And you can here: http://forums.exophase.com/showthread.php?t=9447
This one gets you to 5.00 M33-6 in one simple step. No need to juggle around firmware files and go up sequentially.Q: What should I do with my 32 MB memory stick?
A: Use it for something else. It's pretty much worthless at this point.Q: What if my firmware isn't high enough to downgrade?
A: Upgrade it to any of the games that you play...or download it. (I upgraded my friend's to 3.51 via FFT)
