According to the 'official specs' of the 4315 .... the max memory supported is 2 GB ... sometimes going higher then the official maximum works ... most times it doesn't. However, I have read this (the its refers to the motherboard) ... quoted below:
'If its the same as the 5315 then 3Gb should work with the 1Gb chip in the lower slot (ie the slot closest to the motherboard)."
All you can do is try and hope for the best.