i upgraded the ram in my 522, but didn't look at the APU.
the C50 APU is a chip-on-board, it's not meant to be replaced or removed.
as such, the mobo likely isn't flexible capable of recognizing anything other than a C50 APU.
even if it could, i'm not certain any other AMD APU (such as an E350) would even fit.
and on top of that, where would you even find an E350 APU by itself?