I use PowerColor RX 480 Red Dragon 4GB using Hynix memory.
And after doing some testing I can get 800 H/s for XMR (of course still much below other expert since I'm just newbie).
I use 1266 or 1300 core clock and 2000 memory clock.
Download the bios here
https://mega.nz/#!phlUyCKY!JkLw840lkmP5DekQS0Tjr0Ds_FMxx3f3lKl880lX_To
or just use this straps
BBB000000000000022889D00CECD5939805511113ECF84080048C6006C0014206A8900A00200312
01C143840C5303F17
I know that still can be modified to get better hash, and if someone can do that please share it with me.