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
Upgrading the graphics in our 2011 iMac (first attempt) - YouTube
SOLVED: What GPU's are compatible with iMac 27" 2011? - iMac Intel 27" EMC 2429 - iFixit
Amazon.com: 2 GB Graphics Video Card GPU Upgrade Replacement for Apple iMac Mid-2011 A1312 27 Inch Core i7 3.4 i5 3.1 Desktop Computer, New AMD Radeon HD 6970M HD6970M 2GB MXM Board
iMac 2009 to 2011 (A1311/A1312) Upgrade Guide – MacintoshMen
2011 iMac GPU Upgrade Now with Brightness and Boot menu - Absolutely Worth It! - YouTube
Upgrading an iMac GPU for METAL Support! Late 2009 – Mid 2011 Models - YouTube
For iMac 27" A1312 Mid 2010 2011 upgrade Nvidia Quadro K3100M 4GB GPU Video Card | eBay
SOLVED: What GPU's are compatible with iMac 27" 2011? - iMac Intel 27" EMC 2429 - iFixit
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 :
2011 iMac 27″ GPU failure Fix/Upgrade – JCYCLE
For iMac 27" A1312 Mid 2009 2010 2011 upgrade NVIDIA K3100M 4GB GPU Video Card | eBay
For iMac 21.5" A1311 Mid/Late 2011 6770 AMD upgrade Nvidia K610m 1GB Video Card | eBay
iMac mid 2011 GPU upgrade | MacRumors Forums
iMac 2011 GPU upgrade to NVIDIA 770M with new VBIOS - YouTube