without additional power for the pci slots you will draw all from your atx conenctor and risk to destroy it is very high on the long run if you employ 6 cards....
you are wrong.
Those boards have run 4 rx 480s for months with zero issues it drew 600 watts and used four slots.
the entire three card rig now draws under 550 watts.
the three cards are using 5 pcie cables most power is pcie cable
I also have down clocked to 55% tdp to avoid over heating.
Right now my garage is pretty hot around 90f
You can see the card is warm as it runs at 71 c with fans set to 75%
note is only doing 314 sols due to low tdp of 55% 82 watts 3.83 sols a watt
the middle 1080 ti is doing 522 sols at 55% tdp 142 watts 3.65 sols a watt
and the fat ass aorus is doing 652 sols at 59 % 163 watts 4.00 sols a watt using 2 8 pin pcie cables