Mix-and-matched GPUs from different brands?
I'm considering purchasing a second 7870 GHz Edition for my PC - though I'm also split in the decision to do that or just buy a new single GPU to avoid CrossFire incompatibilities - though the card in my computer is rather scarce. I would like to know if it's okay to mix different brands, like say, an XFX 7870 with a PowerColor 7870. As they both use the same architecture designed by the same company (AMD), I imagine it would be fine so long as the clock speeds are the same to prevent bottlenecking. Is that true?