Endless Paradigm

is it possible to use an eboot to upgrade the firmware of a non custom psp? not from umd's or the internet but, for example, a 390.pbp in the game folder.

A NON CUSTOM PSP!!!!!!!!!!!!!!!!!!!!!!!

from what i know, a 390.pbp is just the official 3.90 firmware upgrade renamed.
if its an official sony upgrade then it will work.
rename it to eboot.pbp and put it in ms0://PSP/GAME/UPDATE/(eboot.pbp here)
and it should launch on any official firmware.

thanks a lot