I’m currently running a 3x R9 280x (1 gigabyte OC rev2, 2 sapphire vapor-x) rig with 2 card plugged into 16x slot, 1 card on 1x-16x powered riser. Mobo is asrock 970 extreme4, xfx 1250w black psu. Power consumption was 960w at wall, now 820w after undervolting cards to 1.094v.
I want to add another 280x asus dc2t. It is safe for the mobo to use 1x-16x unpowered riser for this 4th card?
Both gigabyte and vaporx have 8+8 pin power connector which should theoretically deliver 2x150w to the card leaving little or no power to be required via pci-e/mobo slots. Asus has 6+8 pin connector which can deliver 75w+150w leaving 25-75w to be delivered via the 1x-16 unpowered riser.
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