How to Upgrade/Replace GPU Graphics Card on Mid-2011 21.5" iMac - YouTube
iMac 2010 GPU in 2011 | MacRumors Forums
Amazon.com: Valley Of The Sun Genuine Graphics Video Card Replacement for Apple iMac Mid-2010 Core i5 A1312 27-Inch MC511LL/A MC511 Desktop PC, ATI Mobility Radeon HD 5750 GDDR5 1GB MXM VGA Board
Amazon.com: Valley Of The Sun Genuine Graphics Video Card Replacement for Apple iMac Mid-2010 Core i5 A1312 27-Inch MC511LL/A MC511 Desktop PC, ATI Mobility Radeon HD 5750 GDDR5 1GB MXM VGA Board
Amazon.com: New HD 6970M 2GB Graphics Card Replacement for iMac Mid-2011 27" All-in-One Desktop PC Core i7 3.4 MD063LL/A MD063, AMD Radeon HD6970M HD6970 GPU Upgrade MXM Video Board Repair Parts :
Amazon.com: Valley Of The Sun 2GB Graphics Video Card Upgrade for Apple iMac Mid-2011 27 Inch Core i5 MC814LL/A MC814 A1312 Desktop All-in-One PC, AMD Mobility Radeon HD 6970M Replacement Repair Parts :