Hello same problem for me, it does not work on a 16x 3.0 port ... Thermaltake has changed my cable , but the problem is the same with the new cable ... it only works on a 2.0 port x1 ... well on my graphics card works fine when it is connected directly to a 16x 3.0 port ... it is really damaging , because the Core P5 loses much of its charm to have to use the graphics card without riser ... FYI , I have a GTX980ti , and I tested the riser in two different motherboards, a R5E and a X99 -PRO ...