There are three screws that hold the heatsink and GPU to the board. Here is the detailed guide for how to take the motherboard out on the 2011 iMac. I suggest putting your screws down in order, which makes sure you remember where to put them back. Also, just make sure to take a picture of all the cords and screws as you bring them out. You should need to undo the power supply to get the motherboard out. After that, the whole monitor should pop out right away. At the bottom of the screen, disconnect the power supply and camera cable with the same technique. Moving onto the right side, look for the monitor cable and use your finger to slide it out from underneath. Starting by opening your iMac from the top, you can easily spot the vertical sync cable on the top left. Now, use your fingernail to pop it out and gently pull the cable away from the back of the computer. How to Upgrade 2011 iMac Graphics Card Step 1: Taking Off the Screen

Plus, the chipset has already support from 10.8.3 onwards. Personally, I think I would like to recommend this one because it’s very affordable ( $14 on eBay). In this article, I will be attempting to upgrade from the factory 6770m to an NVidia K610m in my 2011 27-inch iMac. The above graphics cards also support brightness control as well as boot screens via VBIOS flash. Here is the list of recommended graphics cards: Additionally, there is no other GPU variant that has MacOS driver support.

Both of these will help you get full graphics acceleration with all current MacOS versions including macOS Big Sur. Note that only Nvidia Kepler cards or AMD Ellesmere/Polaris cards will work in the 2011 iMac.

How to flash video card for mac