Hello gus..
I have some rigs with RX 480 cards (5 or 6 cards each one) and i use 2 psu x 850W in each Rig.
Now i am making some R9 390 rigs.. But i can see that i will need at least 850W PSU for 2 cards.. I tryed to power on 3 cards on a 1000W gold plus PSU and sometimes it goes off..
Is this normal?
For stock cards, or cards with a mild undervolt and a lot of overclock, you're looking at probably 300ish watts PER CARD.
If you can get them undervolted enough and don't push them super hard, 1000 watts for the entire system should be viable but might still be marginal.
Don't forget the rest of the parts in your system also eat SOME power, not just the GPUs.
Also, not all "1000 watt" power supplies are created equal, though MOST "gold-rated" should be able to handle their 1000 watt ratting for a while at least.
You might also need to check how the +12vdc power rails are set up on your power supply, you might be overloading one specific rail and not the whole PS.
For reference, the R9 390 is a R9 290 with slightly faster memory and an updated BIOS - my "bigrig" with 3x R9 290s using a modded TheStilt "undervolt+tighten up timings+turn off some of the ROPs" bios goes through a little over 1000 watts at the wall with the cards clocked at 1100/1250 on ETH mining (reference cards stock clocks 947/1250).
