Wait, you are using those clocks for mining?
No, that's wrong if its the case, if you mine ETH, set the clock to 1200mhz Core Min, 1300 Core Max, Voltage 881 or the lowest you can set, and memory to a max of 2100 or 10-20mhz lower if its unstable. That gives you around 61-62 Mhs at 150w. I let my 6800XT mine ETH whenever I can, it stays at 61.5 Mhs all the time without a hitch.
The fan auto ramp could be because it gets quite hot, using the settings above would help a lot with temps while mining.