原帖由： Owen Cunneely ,
From what I have seen all the GPU's of the 2011 27" iMacs are interchangeable so you could switch the card out. The same motherboard is used for each of the 27" iMacs there is just a different processor and GPU as well as other components. Unfortunately I don't think that a 27" GPU will fit in a 21.5" iMac because the 27" iMacs (i believe) have a longer GPU card that has to have a different heat sink which couldn't be put in the 21.5" iMac. you could always try to see if the card could fit in the 21.5" iMac if you have a spare one lying around but the card only would have to be changed and not the heat sink. Tell us your results and hope this helps.