Vann is correct and I have few on powered pc risers as I type
But i bet you have a newer MOBO with PCI-e 2.0 or 3.0 and i know these work just fine, but i have PCI-e 1.0 and it worries me. Guess nobody uses these anymore and i will just have to risk it and test for myself.
i'm running gtx1080 and gtx1080ti on old socket am2+ mobo with athlon64 x2 - work like a charm ))