I am trying to properly identify the graphics card used in the 2015 27" retina iMac.
The reason being : I use Ubuntu and getting the new AMDGPU drivers for 16.04 working depends on the chipset.
However, OSX reports two different cards and Ubuntu also reports two different cards according to where you look.
I have asked over in Ubuntu land here :
and I have asked over in Mac land here :
However, the mac forum's general opinion is 'how dare I even be questioning Mac's authority' (said in a southpark accent)
I appreciate that when manufacturing a graphics card the product/model is not always updated on all it's chips in the chipset, so the difference in answer could be according to how you are asking the question.
Any help appreciated - thanks