I have an R9 270, and my friend is upgrading and is giving me his old HD 7970. Will these two cards crossfire with each other? I know that less powerful card will limit the other, but I am just wondering if they are even compatible. I know that there's some leeway with crossfire, and the two cards don't necessarily need to be the same, but is this too much of a difference for this to work?
Nope, https://support.amd.com/en-us/kb-articles/Pages/Crossfire-Chart.aspx