Can you upgrade the RAM in the 27-inch iMac? | iMore
Install memory in an iMac - Apple Support
How (And Why) To Install More RAM In Your iMac
Buy Timetec 8GB KIT2x4GB Compatible for Apple DDR3 1067MHz 1066MHz PC3-8500 CL7 for Mac Book, Mac Book Pro, iMac, Mac Mini Late 2008, EarlyMidLate 2009, Mid 2010 SODIMM Memory MAC RAM Upgrade