I messed around like a fool for twelwe hours yesterday to get my two rigs flashed and running.
I started out struggeling like a maniac on the 16.7.2 driver, that was my first misstake. Dont even try that, i wasted many hours on that crap driver.
When i went with the 16.8.2 driver things started to work better.
I flashed one card with Boyises 31.25 bios and also got it up and running for a few minutes before i started to flash the rest of my cards.
When i had all cards flashed and rigs ready i moved them back to their mining location and fired them up. After five minute i had serious problems. Both rigs mined perfectly at 31.5Mhs per gpu för a couple of minutes before one or two cards went to 0 before the driver crashed and systems rebooted. At that point i was ready to shoot my rigs and then myself. I just shut everything down after some attempts to sort it out.
Today i started the day with rebuilding one of the rigs, fresh installation of win 10 and then flashed one card back to original bios. This time i used the "RX480-30MhOTBLowEnergy" bios. After getting the rig ready for mining with that single card i let it run for like one hour and it was rock solid @ 30.5Mhs.
I flashed the rest of the gpus and did the same to my other rig. They are now up and running really solid.
This is how i did it on my systems:
Setup:
Asrock H81 BTC Pro
Celeron G1820
8Gb ram
64Gb SSD with Windows 10
Corsair RM 850
4 x RX 480 8Gb reference cards (MSI/Sapphire)
Powered USB risers (One riser per SATA line, dont use more because the connector get HOT. I have melted one myself while running two risers on the same line)
DETAILED Installation for noobs like myself !
Leave one card with original bios, flash all other cards one by one with the custom bios.
For flashing i used Winflash 2.74. that version supports Polaris.
In Windows:
Place the winflash files in a folder named "winflash" in C: root.
Place the bios in the same folder and name it bios.rom
When that is done, right click on the windows menu and click on "Command Prompt (Admin)
Back up to C: root using the command "cd.. + enter" several times.
When you are at "C:\>" go to winflash folder: "cd winflash"
When you see this: "C:\Winflash>" you are at the right place.
Be sure to have removed all other cards or unplug the risers/power cables except för the card you want to flash.
Start flashing it with the command: atiwinflash -f -p 0 bios.rom
Note that i had my card in slot "p 0" that is the pcie slot number.
Now it should be flashing and it will take around 20-30 seconds.
After it is finished, reboot your system to see that it aint dead "black picture"
If it works flash the rest of you gpu:s except the one that you keep as original.
When all other cards are flashed, leave theme at side and put your card with original bios in the system. Be sure to clean any old drivers.
Install the 16.8.2 driver, only driver and utility.
When the driver is installed and rebooted you can flash this card with the custom bios also.
When the card is flashed you can start adding the rest of the cards one by one until all cards are detected by windows. Note that they will not be supported by the driver at this point.
When all cards are detected you are almost ready to go.
Now you need to reboot your system with holding your left Shift key when pressing reboot.
You will see a menu now and you will pick Troubleshoot + advanced + startup settings + restart.
In the menu at boot you choose option 4 to get in safe mode.
In safe mode navigate to: C:\Windows\System32\drivers
Replace the file atikmdag.sys with the modified one.
After that, reboot again with left shift pressed down.
Again choose: Troubleshoot + advanced + startup settings + restart
In the menu at boot choose option 7
You should now boot into windows and all your cards should be accepted by the driver and ready to start mining.
Any custom bios should work but try one out on one card first and see that it is stable before flashing the rest of you gpu:s. Also remember to backup your original bios, i used GPU-Z tp pull out my original bios.
Links:
Winflash 2.74:
https://www.techpowerup.com/downloads/2728/atiflash-2-74Bios: There are many around, i used one called "RX480-30MhOTBLowEnergy"
Modded atikmdag.sys file :
http://www.win-raid.com/t892f16-AMD-and-Nvidia-GOP-update-No-requests-DIY-19.html#msg30028