Answer to "Graphics card upgrade on 27" iMac 2011?"If your so willing, most nvidia mxm cards will work with the web driver... take a look at this.... https://www.ifixit.com/Story/18646/Succe...
Answer to "What GPU's are compatible with iMac 27" 2011?"Most nvidia GPUs will work if you install the web drivers. Take a look at this... https://www.ifixit.com/Story/18646/Succe...