Hi, I have 8 XFX AMD Radeon RX580s, two Crimson and six White. They have been nothing but problems. As in this thread and the youtube video posted below, all over the internet there are resources showing how overclocking can result in 27-30 Mh/s mining rates with these GPUs. However, I have not seen anyone report consistent results after long periods of mining. In my hands, I can achieve stable mining for a few days to a week. However, I am currently left with 6 "bricked" cards. First, each showed strange, inconsistent operation. For instance, the computer would crash, with some of the cards left with LEDs on and fans spinning, others completely lights out as would be expected with the motherboard off. In another case, the card would run but the fans would not, so the card would start at a a high speed, then quickly drop to zero because I limited the temp to 71C. In each case, I would switch the bios back to the stock position. Sometimes this worked, sometimes not. When I was able to still recognize the card in the stock bios switch position, I would flip the switch back to the position I switch the bios and re-flash with the saved stock bios. After confirming the card was stable with the re-flashed stock bios, I tried re-flashing the modded bios (eg what it shown in this video using Polaris Bios Editor and ATIwinflash). Once again, I would get good operation for a while.. But ultimately, I am now left with 6 bricked cards unable to mine, the hardness for ether is doubled, the price of ether is half, and I've wasted over 100 hours troubleshooting and stuck with a three thousand dollar credit card bill. After over a month, I've earned only 1.4 ethereum.
The whole endeavor has been a lesson in the pain of noobery and why not to do projects outside of my wheelhouse. I knew there was a risk in the volatility of the currency, but had no idea how fringy the mining technology is. Running 6 or more overclocked GPUs is presented as legitimate, but in reality it appear we are pushing these machines to beyond what they are designed to do. Thus, there is a huge risk that the calculated ROI on paper will unlikely become reality.
Ultimately, I realize that my personal experience is a "one off", but the whole endeavor is unscientific because everything we find on the internet is self-reported and there is rarely follow up from users over the long term with users who report "success" after finally getting a system running, as I did, with a modded bios.
A review of how terrible these particular RX580's are: https://www.youtube.com/watch?v=WN4scGyBxwA