Amazon.com: Sunvalley 2GB Graphics Video Card Replacement for Apple iMac Mid-2011 27 Inch A1312 Core i7 3.4 MD063LL/A MD063 Desktop PC Computer, ATI Radeon HD 6970 GDDR5 2 GB, New GPU Upgrade
late 2014 iMac 5k with 8GB of Ram graphic… - Apple Community
Amazon.com: Original Graphics Card GPU Replacement, for Apple iMac Late 2009 A1312 MC507LL/A 27-Inch Core i7 2.8 27-Inch Computer, AMD Radeon HD4850 HD 4850 GDDR3 512MB, MXM GPU Video Board Repair Parts :
iMac (Late 2012) | Low End Mac
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How to upgrade a Mac: Swap in new RAM, graphics card, hard drive and more | Macworld