For iMac 27" A1312 Mid 2009 2010 2011 upgrade NVIDIA K4100M 4GB GPU Video Card | eBay
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
2011 iMac GPU Upgrade Now with Brightness and Boot menu - Absolutely Worth It! - YouTube
iMac Intel 27" EMC 2374, AMD Radeon HD 4850 Video Card Removal & Repair - iFixit Repair Guide
iMac 2009 to 2011 (A1311/A1312) Upgrade Guide – MacintoshMen
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 :
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 Graphics Video Card GPU Replacement for Apple iMac Mid-2010 A1311 Core i3 3.06 MC508LL/A MC508 21.5 Inch Desktop Computer, ATI Radeon HD 4670 GDDR3 256MB, MXM VGA
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
2010 iMac GPU Upgrade to NVIDIA GTX 765M - YouTube