A:Answer DDR3 SODIMMS for laptops com in 1.5 volt and
1.3 v versions you can tell by the "L' on the label
1.5 v are marked 1.5 v, and they are not interchangeable
It is best to use 2 identical SODIMMS, as this insure
Dual Channel Operation. Also, if one SDIMM IS slowe,
All RAM will run at the lowest speed RAM Card.
My advice is
Match the 4G SODIMM with another of the same voltage
And speed.
Power off computer and remove battery
Install new SODIMM
REBOOT. You maybe asked to update BIOS. Choose y