my rig won't turn on with risers

[Trigun]

hello
i just bought a new rig...
i have 280x and asrock k87 killer fatal1ty
if i turn on the mobo without any gpu it start without problem
if i add a riser 1 16 the psu try to start (the fan move for 1 cm :-P) but after that is all powered off... (i can see the sapphire write blink for an instant during this time)

i made the bridge on the pci 1x ... but the result is still the same

any tips?

[ineedit]

hello
i just bought a new rig...
i have 280x and asrock k87 killer fatal1ty
if i turn on the mobo without any gpu it start without problem
if i add a riser 1 16 the psu try to start (the fan move for 1 cm :-P) but after that is all powered off... (i can see the sapphire write blink for an instant during this time)

i made the bridge on the pci 1x ... but the result is still the same

any tips?

The primary video card should be on a x16 to x16 riser or the driver may not work.