If 4GB is installed, the recognized memory may be reduced to 3.5GB or less (depending on system configuration and memory allocation). Maximum configurations require a 64-bit operating system.
DDR3 1600MT/s Non-ECC Unbuffered SODIMM CL11 1RX8 1.35V 204-pin 4Gbit
DDR3 1600MT/s Non-ECC Unbuffered SODIMM CL11 2RX8 1.35V 204-pin 4Gbit
DDR3 1600MT/s Non-ECC Unbuffered SODIMM CL11 1RX16 1.35V 204-pin 4Gbit