How to upgrade the memory of a 27-inch iMac with Retina 5K display (Late 2014 - Mid 2015) iMac15,1 - YouTube
Install memory in an iMac - Apple Support
How to Upgrade Memory in a Late 2009 21.5-inch or 27-inch iMac - YouTube
Benefits from RAM upgrade to Late 2009 iMac | MacRumors Forums
Apple iMac 2009 (Late) Core 2 Duo 3.06Ghz 21.5-inch (iMac 10,1) SSD ,Ram & OSX Upgrades - ZD Laptop Service Centre
Install memory in an iMac - Apple Support
Is it worth upgrading my ram on a Late 2009 iMac? New iMacs/MacBooks are very pricey. It's currently running on 4GB of RAM & it has a 3.06GHz Intel Core Duo Processor. :
Apple iMac 2009 (Late) 27-inch 2K (iMac 11,1) SSD ,Ram & OSX Upgrades - ZD Laptop Service Centre