I have the HEAVY ROM installed which is supposed to do 31-32MH and does. However it will crash my system after just running for 1minute every time. This is for both solo and Dual mining both with risers and direct on the MB. The power draw at the wall is around 160-220 watts for the RX480 depending on solo or dual mining. Don't just look at GPU-Z as its not reporting the PCI-E draw from the riser or MB.
The powersaving ROM at 29MH seems more stable. Using Killawatt at the wall it's pull 185-190. Deduct 55 watts for my system to get the RX480 card use. Pretty impressive for 29MH using 130Watts with 16.7.3 driver. When I upgrade to 16.8.2 I get the same performance but at 15-20 more watts usage.
Will try Boysie ROM next.
Update - Same stability issues with Boysie's ROM which uses the most amount of wattage. So far only the Powersaving 29MH ROM is stable for me.
Maybe your PCIE slot cannot support the 75W draw. You might use a powered PCIE riser to test the stability.
I think you may have missed the sentence where I mentioned I test both direct on the MB and via risers (powered). I was chatting with other members on the Ethereum forum and it was working for them (MSI card) for over 2 days so it's something unique with my cards (XFX) perhaps since I'm using it on the same MB combo as everyone. The Boysie ROM I was using was actually designed for XFX so I don't know what the deal is. I even test it using a fresh new install OS, same issue. Been running the LowPower ROM from this thread for 29MH at 130W since last night. It works for Eth only with great power saving, it's not designed for Dual mining. I need to get the Heavy version working as I want the highest hash rate for dual mining.