7950 rig issues

[ayayay]

my rig has 3x 7950---  an asrock 990fx extreme4 --      amd sempron     



I'm having problems with it posting, the rig runs all fans and the system seem to turn on but I get no display, the mother board show a 19 in the digital readout.

any ideas for a fix

[cad_cdn]

can you boot with 1 gpu plugged in?
I found my new gigabyte had an issue of the pcie x slots and had to try each one until.
also had a loose pcie molex connector that didn't supply proper power to pci 6 pin on gpu's 'check the simple things' first.