parts-quick 8GB DDR3 Memory for HP Compaq ProBook 4540s PC3-12800S 204 pin 1600MHz SODIMM Laptop Compatible RAM at Amazon.com
HP ProBook 4540s 15.6" Intel Core i3-3110M 2.4GHz / 4GB / 500GB vs HP ProBook 650 G1 15.6" Intel Core i5-4300M 2.6GHz / 8GB / 750GB: What is the difference?