At 9.0 there are now such saws. 480 8 ref 1150/2100. At 8.1 was not. Driver 16.6.

Nearly the same for me with a rx 480 red devil 8gb 1200/2250 and Driver 17.3.3 i guess
Same with Sapphire RX480 8GB Refference, the memory controller load is going to 75% for a few seconds and then again to 100%. There was no such problem with 7.3 which I was using before 9.0.