My 27" iMac has recently been repaired by an Apple Service Agent. To rectify a "White Screen" fault the repair report enclosed with the returned computer simply states under resolution " Video Card Replaced". Is there some way of checking the spec of the new Video Card. The card it replaced was an AMD Radeon HD 6970M 1GB GDDRS which was a higher spec than the standard card at the time (Mid 2011). I am just concerned that the replacement may not be the same spec. Any advice most welcome.