Apple Initiates Video Card Replacement Program for Radeon HD 6970M Equipped Mid-2011 27” iMacs
2GB Graphics Video Card Improve for Apple iMac Mid-2011 27 Inch Core i5 MC814LL/A MC814 A1312 Desktop All-in-One PC, AMD Mobility Radeon HD 6970M Alternative Restore Elements - Top Motherboards
Upgrading an iMac GPU for METAL Support! Late 2009 – Mid 2011 Models - YouTube