2x r9 290 and one rx 580 8gb, 850w?

[culzone]

Would 850w be enough for all three cards while mining? Maybe some undervoltage needed? Cant afford new psu :S
R9 290 sapphire founders
Rx 580 8gb nitro

 

[Legitgamer1261]

yes but I would under volt by ~10% each for safety

 

[culzone]

So if it runs 1.200 i should undervolt 12mv etc?