Linux (GUI): install and run GParted, select your MS, right click on the primary partition (there should only be one anyway), select 'format as' and 'fat16', click on 'apply'. Linux (CLI): the command to format in FAT16 is 'sudo mkdosfs -F 16 /dev/sdx', change sdx with your MS device number. Go to your 'Computer' folder, right click on the MS and select 'format', under formatting choose FAT16. Windows: insert your MS in you PC (with your PS or an adaptor).
The PSP can read FAT16 faster than FAT32, the problem is the PSP will format in FAT32 anything with more than 2GB, so you have to manually format it with a PC: (This trick is for 4GB and up, if your MS is 2GB or less and still experience slowlyness, skip this).
The standard formatting for MS is FAT16 for upto 2GB and FAT32 for anything beyond. If (like me) you have ever experienced slow read/write operations on your Memory Stick, here are good advices to speed up your MS.
