I have only one PCI Express x16
I just tried with a GT440 and it still doesn't work. I tried the GTX 960 GPU on another machine running GNU/Linux and it worked so it is not a FreeBSD issue but seems to be a motherboard (configuration ?) issue
Yes because I tried with Debian, Arch Linux and OpenSUSE before FreeBSD (where I decided to stop). nouveau video driver is working but as soon as I install nVidia driver, I can't start X anymore.
Every try were chaotic, nothing worked. I can't understand why ON THIS MACHINE it doesn't work.