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Install memory in an iMac - Apple Support
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Timetec 16GB KIT(4x4GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 CL7 Dual Rank for iMac (Late 2009 21.5-inch / 27-inch) SODIMM Memory MAC RAM Upgrade for iMac 10,1 and iMac 11,1 at Amazon.com
iMac (21.5-inch, Late 2009) SSD Upgrade - YouTube
Reemplazo del la RAM EMC 2428 en tu iMac Intel 21.5" - Guía de reparación iFixit
Install memory in an iMac - Apple Support
Fair Condition*: Apple iMac 21.5-inch 3.06GHz Core 2 Duo (Late 2009) MB950LL/A | mac of all trades