Can I upgrade my Graphic card?

Apple offered three versions of the AMD Radeon graphics board the one you have 6770 with 512MB of VRAM or a 6970 with 1 or 2 GB of VRAM.

• AMD Radeon HD 6970 1GB - Apple P/N 661-5968
• AMD Radeon HD 6970 2GB - Apple P/N 661-5969

You may really need more RAM and a faster drive Vs this major upgrade:

• Lets start off with RAM. If your system has the newest EFI firmware you can up your system to unto 32 GB! I wouldn't go that high to start off, how about going to 16 GB first and see how that works. Here's the Apple T/N: About EFI and SMC firmware updates for Intel-based Mac computers.

• I would then look at adding a second drive in your system. In this case you want a good SSD. Follow this IFIXIT guide: Installing iMac Intel 27" EMC 2429 Dual Hard Drive Kit. Once you get it up and running you want to make it your boot drive. As to the size I would get a 512 GB if you are working on very large drawings or vids you may want a full 1 TB drive.

If you really want to go with the graphics board upgrade its quite a bit of work! You may want to think twice here and see if you can get someone with good iMac repair skills to do it for you (even the SSD upgrade). The steps are the same as the SSD upgrade but unlike it you'll need to take the logic board fully out. Here's a vid on the steps: Removing the Fan and Logic Board. Once you get the logic board out you'll need to take the graphics card off.

As to getting the part you'll need to do a bit of searching using the Apple part number with the word Apple prefixing it.

The last thing here is your network connection unlike many apps Adobe CC accesses Adobe's servers so make sure your network connection is good.