The following is a list of official firmwares(versions) Sony ever released for the PSP:
1.00
1.50
1.51
1.52
2.00*
2.01
2.50*
2.60*
2.70
2.71*
2.80*
2.81
2.82
3.00
3.01
3.02
3.03*
3.10
3.11
3.30
3.40
3.50*
3.51
3.52
3.60+
3.70
3.71
3.72
3.73
3.80
3.90
3.93
*These firmwares can be downgraded to firmware 1.50 (the 'magic' firmware). If the PSP is on a firmware between two asterisks(*), then upgrade it to the star with the higher firmware (excluding firmwares lower than 2.00). If the PSP is on a firmware with an asterisk, then it can be downgraded to firmware 1.50. The PSP cannot be downgraded if it is on firmware 3.51 or higher at the moment.
+Introduction of PSP Slim.
TO DOWNGRADE FIRMWARE 3.03 to firmware 1.50, the game Grand Theft Auto: Liberty City Stories is required in UMD form. That means, it is required to go to a store (or an online store) and buy one. This downgrade is for firmwares between 2.81 and 3.03. However, GTA:LCS has been patched lately in order to close this "security break". Thus, the GTA:LCS game in stores are also patched, which means go look on eBay. However, don't lose hope. Look right down below.
TO DOWNGRADE FIRMWARE 3.50 to firmware 1.50, the game Lumines is required in UMD form. There are no patched Lumines yet, except for Japanese Lumines game in Japan. Lumines in other regions are starting to be patched, so buy soon! However, Lumines is much easier to find. This is the only option for downgrade if the PSP is on a firmware between 3.10 and 3.50.
FAQ
Q: Why should I downgrade my PSP?
A: Downgrading allows the PSP to install a custom firmware and thus, allow the user to play downloaded games.
Q: What is a custom firmware?
A: Custom firmware is a special, modified firmware that has extra capabilities that allows the user to play downloaded PSP games or user-created PSP homebrew games. It also allows for use of custom themes and other software modifications to the PSP.
Q: Ok, after I downloaded a game, how do I use it and play it?
A: The downloaded game after extraction is either with an extension .ISO or .CSO. These are game images, which the PSP reads if it is on a custom firmware. In order to use these formats, transfer the specified game onto the memory stick under the directory:
P:\ISO\
where P is the letter of the PSP drive. After it is done transferring, navigate to the Memory Stick icon under GAME in the XMB and the game transferred should appear.
Q: What is the XMB?
A: The XMB stands for "Cross Media Bar". It is the interface the PSP uses, as well as many Sony products such as the PS3 and new Bravia LCD TVs.
Q: How do I extract these downloaded files with .RAR extension?
A: The .RAR extension is a compression file. To extract it, use the program winRAR 3.71. Open only one part (filename.part1.rar) and drag the contents inside that part to a place on the computer (desktop, My Documents, etc). Once extraction is completed, you should have an ISO or CSO file, and the parts. The parts downloaded may be deleted after extraction is complete.
Q: I ran the game I downloaded on the PSP, but nothing shows up. Just a black screen. Sometimes the PSP shows an error message: "The game cannot be opened".
A: Be sure that the UMD driver in Recovery Mode is set to either M33 Driver or Sony NP9660. Also check if the game requires a later firmware; if so, then update to a higher firmware, but still keeping the custom firmware. If problem still persists, format the memory stick from the PSP. Be sure to backup everything before formatting.
Q: How do I access the Recovery Mode?
A: Turn off the PSP completely. Then hold the R shoulder button while turning the PSP on.
3.50 Downgrader
This downgrader is brought to the community by Fanjita.
This downgrader requires the UMD game LUMINES. It is much easier and more available to find than GTA:LCS, so now everyone with a PSP can downgrade their PSPs to 1.50. Your PSP version MUST be on firmware 3.50 in order to use this downgrader.
The downgrade files and instruction are here:
http://rapidshare.com/files/11537474...WNGRADE_FL.rarThis is the firmware 1.50 EBOOT, required to downgrade:
http://rapidshare.com/files/11533474...intfive_FL.rarIf you need to update to 3.50 first, the update file is here:
http://rapidshare.com/files/11537999...eUPDATE_FL.rarThis is all of the files above combined:
http://rapidshare.com/files/11532301...nt5DOWN_FL.rar Older Custom Firmware Section
3.71 M33 Custom Firmware
http://rapidshare.com/files/11533623..._UPDATE_FL.rar3.71 M33-2 Update:
http://rapidshare.com/files/11532553...DATE_FL_1_.rar3.71 1.50 kernel update:
http://rapidshare.com/files/11532435..._UPDATE_FL.rar3.71 1.50 kernel update 2:
http://rapidshare.com/files/11532553...DATE_FL_1_.rar
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