iMac 2009 / 2010 / 2011 GPU upgrade — Fixing LED/LCD PWM brightness with an ESP32 | by Fixing Things | Medium
iMac 2011 GPU upgrade to NVIDIA 770M with new VBIOS - YouTube
2011 iMac GPU Upgrade Now with Brightness and Boot menu - Absolutely Worth It! - YouTube
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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
Amazon.com: GDDR5 2GB Graphics Video Card Radeon HD 6970M for Apple iMac Mid-2011 27 Inch Core i5 i7 All-in-One Desktop PC Computer, AMD Radeon HD6970M HD6970 MXM Board GPU Upgrade Repair Parts :