Here is a tutorial for bios modifying Cards like AMD Rx470 / Rx570 and Rx 480 / Rx580
Download Polaris Bios Editor ( https://mega.nz/#!ZjpmnS7J!59EgFtVbIg7bBN0WseSRT50uXSvH45T3QqYiJdY45Do )
Unrar it
Open as Administrator

Click Open Bios

Search and open the bios of your choice

1: Memory Timings (Straps) 2-3 Mhs More !
First we go to the Memory Timings ( Straps ) for the Vram

Then you Copy the 1500er Memory Timings (Straps)

and now Paste the 1500er Memory Timings (Straps) to all higher frequences (1625, 1750, 2000)

2: Powersave ( reduce wattage to 80-90w = Rx470 / Rx570 , 90-100w = Rx480 / Rx580 )
Now Go To Powertune

Set the original Values down to 100 TDP(W) and MAX POWER LIMIT(W) 120
MAX POWER LIMIT(W) is by Most cards 120W Standart, this is the Sapphire Bios here it is by 160W set it Down to 120-140.
Other Cards Like Powercolor Red Dragon, Asus Expedition, MSI Gaming X etc runs with 100-120Watt setting in Max Power Limit (W) stable!!!

3: Overclocking ( Set Rx470 / Rx570 up to 27-29 MH/s, Rx480 / Rx580 4GB up to 28-30 MH/s and Rx480 / Rx580 8GB up to 29-32 MH/s !!!
Go to GPU

Here you Set Gpu Core Clock in last 3 States @1125 Mhz
Maybe your GPU had a better Chip and Runs @Higher Clocks, Try it !

Go to Memory

Here you Overclock the Vram ( Video Memory )
Most Rx470 / Rx570 makes 2000Mhz
Most Rx480 / Rx580 4GB makes 2000Mhz
Most Rx480 / Rx580 8GB makes up to 2150Mhz
Have Rejects or falling Hastrate after Moddifying try Lower Clocks like 1950MHz

Now Save the Bios and try it Out :D

Sapphire Rx 570 Nitro+ Original Bios
https://mega.nz/#!xzBh1JzY!Z02jmuEaFNjXqsJe11NFUNO-uLwKv86WRgvDtDjNY90
Sapphire Rx 570 Nitro+ modifying (Powersave, Overclock, 1500 Memory Timings up to 2000 ( Straps) Bios 80-90W
https://mega.nz/#!cq4WHD7R!P7kU6SeM64wn7HlLl3wqYB48JqfKm4uKag1Kawv7VZM
ETH donations to: 0x9b70fcff8d8291dc028f2dc6ea6612e10fa6721a
Thanks for this! Trixx wont save any of the settings so will give this a try!
Tried this. Works like a charm