"At this point, we could not find the main CPU"
If it's anything like the DS, it'll be underneath the slot for the DS game. I pulled my old DS phat apart last night and underneath the silver tray for the cartrige there was a small black square that said "CPU NTR ARM". Maybe the 3DS's is located in the same spot, however it requires some un-soldering... which no one probably wants to do to their brand new 3DS lol.
I'm interested in finding out too.
You didn't finish reading did you?
http://techon.nikkeibp.co.jp/english/NEWS_...0110301/189976/ QUOTEAfter briefly examining the top and back sides of the main board, we realized an important thing: We could not find the main CPU. There was only one possibility left: under the slot for game cartridges. There were many passive components embedded on the back of the slot.
We managed to remove the slot, which was firmly fixed on the board, by using a soldering iron, etc. Then, the main CPU of the 3DS printed with the characters "Nintendo" and "ARM" appeared. A chip found next to the CPU was printed with "F JAPAN" and "M82M808080." It seemed to be Fujitsu Semiconductor Ltd's FCRAM.