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iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
NEMIX RAM 16GB Memory Upgrade Kit (2x8GB) DDR3L 1600MHz PC3L-12800 SODIMM Compatible for Apple for Mac Book Pro(Early/Mid 2012), iMac, Mac Min at Amazon.com
CMS 32GB (4X8GB) DDR3 12800 1600MHz Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I7 3.4 27-Inch (Late 2012) - A6 at Amazon.com