How to Upgrade/Replace GPU Graphics Card on Mid-2011 21.5" iMac - YouTube
Sunvalley 2 GB Grafikkarte GPU Upgrade Ersatz, für for iMac 27 Zoll Mitte 2011 A1312 Desktop
Amazon.com: Original 2GB Graphics Video Card Upgrade Replacement for Apple iMac Mid-2011 27 Inch A1312 Core i7 3.4 MD063LL/A MD063 Desktop PC Computer, AMD ATI Radeon HD 6970 Spare Parts Full Tested :