Hmm, well that means you don't need a modded ROM, this default ROM is already 99 Watts, so should be able to have even 6 of these cards on a 1000 Watt PSU.
The only benefit I see for making a custom ROM is trying to get the VRAM higher default clocks and Lower the CORE Voltages and clocks to be more effecient.
That's weird. I most certainly cannot fit 6 of these on a 1000w. My kill-a-watt puts it over 1000. I guess try to crank down the core and I'll test it.
Here are the ROMS:
https://drive.google.com/open?id=0B6VgxfTqxux4cWFWbUpDelhQWFkI made 2 core variants and 2 memory variants
Try the Stock Mem and Core 1125 mV 850 first, that should be the lowest Wattage ROM that would be named "Asus.RX480.4096.160817_core_1125_mv_850_memory_stock_timing_stock.rom"
If it's stable for more than 2 hours, I would then try the "Asus.RX480.4096.160817_core_1125_mv_850_memory_1900_timing_1650.rom" Which is the ROM with same low power core clocks + 1900 Mhz Mem Clock and 1650 Mhz Straps for better Dagger and Equihash performance.
BTW, do you have multiple GPUs? Incase the ROMS fail on boot, you can reflash the GPU with stock ROM if you have another GPU that you can boot with. (I'm assuming you know how to do with with ATIFlash/ATIWinFlash?)
Awesome! Will test tonight and report back! Yes I have bricked cards, and re-flashed using another GPU before. I use ATIflash cmd line tool.
Ok, cool

Let me know if the ROM Works or if the voltages need to be a bit higher

Mines at 23.5, which is about 2 mhs higher than stock, but crashes after a few minutes. Even with the 860 mv.
Modified the BIOS slightly. Took the 1500 straps and copied it instead of 1625. Getting 27 mhs now with 83-84 watts on GPU-z and 275-80 at the wall with one GPU. Mining for about 20 minutes currently.
I'm sure there are a ton more optimizations that I can make but I used your ROM to compare to stock and other ROM's I have to learn what you did and what it does. Thanks for guiding me along this learning experience. I am happy to throw you some BTC for your time if you wanna post or DM your BTC addy.
Thanks MXaddict.
Wolf, if you want to elaborate what you mean, I would be happy to continue to learn.
A note about timings on RX cards - I've noticed Elpida/Hynix like the 1500 strap better than the others - Samsung seems to prefer 1750, though. What I meant was, the only undervolts done look like they may have been done in Polaris BIOS Editor (which used the voltage table referenced by the PowerPlay DPM states.) I'm almost certain this doesn't work on Linux, but I'm not sure about Windows. So - did it work on Windows (wattage drop)?
I don't think so.
I can watt tool the 470's down, maybe enough to get all 6 cards to fit on one rig, but the 480's are hogs and I have no control over the voltage in watt man, and it appears the cards pull the same amount of power regardless of the ROM, all it affects is hashrate on the Asus.
I think i can pump the memclock to 1960, as most people are reporting hashes in the 28's where my 1900 mem only gets 26.
I am still left with the power issue, regardless if I'm getting 26 or 28 mhs/card. I thought the ROM would supercede the inability to correct the wattage issue through watt tool, but I think I was wrong.
http://forum.ethereum.org/discussion/8845/rx-470-mining/p26 It looks like this guy has the same problem as me. Don't understand the response, though I'll try asking him