Amazon.com: Original Graphics Video Card GPU Upgrade Replacement for Apple iMac 21.5 Inch Late 2011 Core i3 3.1 All-in-One Desktop PC MC978LL/A, AMD ATI Mobility Radeon HD 6750M, MXM VGA Board Repair
Amazon.com: Graphics Video Card for Apple iMac Mid-2011 A1312 Core i5 2.7 27-Inch Desktop PC MC813LL/A, AMD Radeon HD 6770M GDDR5 512MB 109-C29557-00, MXM VGA Board Genuine Replacement Parts : Electronics