hello
I have 3  Gigabyte rx570 gaming 4G with elpida memory
1. max  memory clock 1920 and 27 MH
2. max  memory clock 1870 and 26.7 MH
3. max  memory clock 1800 and 24 MH

bios modify by copy 1500->1625,1750,2000.

How did you reach 30 ??