The architectures are not that different really. NVIDIA has a problem with context switching between compute and graphics, and no hardware scheduling, but they managed to write a driver that seems to feed their GPUs almost to 100% all the time. Asking the same from AMD is no that weird. They did it when they needed to serve Hawaii as a Maxwell competitor, I wonder if they could do it again if they had such a financial incentive. I have no stutter and the framerate is basically stuck at 60 with everything on Ultra, but I get similar glitches.