you can make own custom bios using gpuz to dump your original bios , then modify by using polaris bios editor , just copaste memory strap from 1500 to 2000 or some other combination, save the bios, and flash it using atitool via commandprompt, hwinfo for checking memory error if you overclock the memory
dont worry about bricking if you have multiple card, flash it again and would fix the brick
custom bios polaris is good for ethash & cryptonight it will jump around 20-25% performance
tutorial on youtube
and use msi afterburner for undervolting&underclocking your card
eth at 29mhs consume around 120watt, after mod & undervolting
