Installing Custom Firmware 3.90 M33-3. This article assumes that you have custom firmware (OE/M33) installed on your PSP and want to upgrade to version 3.90 M33-3. If you have OE/M33 firmware lower than 3.52 M33 please start from Section A. You can now delete the folder M33Update4 folder from your PSP. Section C Install custom firmware 3.90 M33 Files to be downloaded and extracted: (a) Custom firmware 3.90 M33 (DL.3) (b) Official firmware update 3.90 (DL.7) Steps to install: (C.1) Copy the folder UPDATE and. Turn on your PSP while holding the right shoulder button to go into recovery mode). Revert your kernel to 3.52. (C.5) In your PSP, browse to your Memory Stick and run the program 3.90 M33. Changes: - Improvements in plugins loading code: Fixed some problems with problematic cards due to filesystem not mounted. Now plugins should read the faster. Problem fixed with lines with spaces at the end. We strongly advise you to take a look at the Readme. txt file for more details on how to install the latest custom firmware on your PSP handheld. Please note that this requires your PSP to have CFW 3.52 M33-3 or higher already installed. Z PSP/GAME 150/ ). (A.2) Rename Official firmware update 1.5 (EBOOT. PBP) to 150.PBP. (A.3) Copy the file to your PSPs memory sticks /PSP/GAME 150/M33CREATOR / folder (eg. Z PSP/GAME 150/M33CREATOR / ). Changes in updater: - The 3.90 eboot downloading code is now more stable, no more freezes after selecting AP - Memory stick write in the 3.90 downloading code is delayed the maximum possible for faster operation (the system prefers big chunks of data written at. PSP CFW 3.90 M33-2. Note: only 3.90 M33-2 and higher can be booted from nand in slim with those ipl loaders, not official Sony firmwares or previous versions of M33. Here's the specifics on the update taken from the Readme: March33 NO UMD: fixed (yet another) bug related with exiting with home. (infinite semaphore wait) The developer also noted the changes in the auto-updater function that was included in the previous version of CFW 3.80.