help gts 250 gigabyte only function on a pcie 4x slot

[harrison24]

hello please i really need some help here..i have tried almost every thing and still then no changes..i just bought a graphic card gts 250 gigabyte and i have two pcie slots on my mobo(hp compaq dc 7900 convertible mini tower) when the card is pluged in on the pcie x16 slot, nothing happends that is automatically the computer boots with the internal graphic card... but when the graphic card is pluged on the pcie slot x4 ,every thing boots fine and the graphic card geos on well....please help me i have done every thing ..that is remove the cosmos battery and resetted my bios but no way..and i was told that a pcie 4x slot is'nt good enough for graphic cards..and for the information i have tried this same graphic card on different mother boards with x16 pcie slots and nothing happends.... i don't know what makes this graphic card to only function on a pci e x4 slots ...any help will.. be welcome ..i have search every where but seems not to have any concrete answers....the card needs an extra 6 pin conector and all power supply i have tested with all have the 6 pin connectors

 

[Cons29]

does the card need an extra 6pin power?

 

[harrison24]

any help please i don't understand what is going on about the whole thing.. REALLY NEED SOMEONE'S HELP