Imac 27" 2009 graphics card replacement

[StanSmithl]

Hello,

I've got a iMac 27" late 2009 and I want to replace my Radeon HD 4850M 512MB withe newest 6970M 2GB board. Has anyone tried this?

 

[COLGeek]

Unless the new video card is "Mac compatible" it will not work. Sorry. You can't stuff a PC GPU into a Mac. There are firmware (software and sometimes hardware) that are the root of this problem.