If I plug in a second or 3rd GPU into 1x slot with riser it does not detect the GPU
If I plug the riser with GPU into 1x slot or 16x slot alone the pc does not boot

When I do that it works with that one card but when I add the rest of the cards individually they are not detected and the fans work on them so there is power on the risers.
I can connect 2 cards in the 2 x PCIE 16 slots but when I connect a riser to the 1x slots for the 3rd card it does not detect it as well

I am using a GTX 1050 ti ,GTX 150 and a GTX 750Ti
I have tried  the cards individual one by one and in different slots but the pc gives a beep and no loading of the screens.
I have upgraded the Bios as well and I cant find any settings for PCIE except the frequency that is 100Mhz

Hi All
I am having a issue with my 990fxa-gd65v2 mobo when I try to add 3 GPU cards to it.
I use 1x-16 SATA power risers but I am unable to get them to enable on the 1x slots on the mobo.
My system is Win 7 64 bit 8 gig memory with a FX4300 CPU 4 core