GPU ATI 216-0811000 Graphic Video IC Chip for iMac 27" A1312 (Mid 2011)
Amazon.com: Sunvalley 2GB Graphics Video Card Replacement for Apple iMac Mid-2011 27 Inch A1312 Core i7 3.4 MD063LL/A MD063 Desktop PC Computer, ATI Radeon HD 6970 GDDR5 2 GB, New GPU Upgrade : Electronics
Apple IMAC 27” A1312 Nvidia Quadro K5000M 4GB MXM Video Card GPU Replace 6970M | eBay