no i am saying there is known problems with the gigabyte motherboards power delivery system.
on the ud7 there is an additional plug you can plug a sata power cable into that supplements the motherboards delivery of power to the pci lanes. this was initially included to help power 3 and 4 card...
same holes, same slot size, pci 3 offers more bandwith to devices that can take advantage of it, graphic cards still do not max out 2.0
i have a pci 3 graphics card, and an amd motherboard, 990fx motherboards have 2.0
i am quite positive
does your mobo have the extra power input for the pci slots?
what version of the 990fxa do you have? ud3? ud5? ud7? what revision?
if it has the extra input as my ud7 does just try it before you spend any more money
i'm betting its mobo power delivery like my issue was
check the board and see if there is an extra sata power input. mine is just above the sata ports on the ud7
apparently gigabyte cheaped out on some of the power system components on some 990fx boards