This FATMSPatch is for custom firmware 4.01 M33 / M33-2. If you are still using the old custom firwmare version read my other post here: PSP Fatmspatch - Lag Fix

Why use FATMSPatch?The fastest recent firmware in terms of psp-memory card access is the 3.71. After 3.71, Sony removed/changed the fatmsmod in 3.80, 3.90 and 4.01.Dark-Alex made a patcher for 3.90 making use of the 3.71 fatmsmod.prx to the firmware. Now we are implementing the same thing, only in 4.01

To install Fatmsmod Patch, follow these steps:

1. Download the files needed
   • fatmspatchfor4.01  
2. Connect your PSP to your PC via USB Mode
    
3. Extract FatmsmodV2.rar anywhere on your PC
   • you can use WinRAR to extract .rar files 
4. Copy the extracted folder “FATMSPATCH” on “\\PSP\GAME\ ” folder of your memory stick
   • e.g. X:\\PSP\GAME (where X is the drive of your memory stick) 
5. Copy fastmsmod.prx on your PSP’s root Directory 
    
6. Exit USB Connection Mode 
    
7. Run the patch in Game and the prx will be flashed/patched. 
    
8. Be sure to check your game speed and set it to default speed and I suggest you use the M33 No UMD driver