My problem is that a PCI Express 2.0 16x compliant video card (Gainward Geforce GTX460 768MB) installed in a PCI Express 2.0 16x slot (on a Intel DP55WG motherboard) seems to run at 1x. This is reported by the video driver and by GPU-Z diagnosis software.
I installed the latest BIOS version on the motherboard and the video card seems to be up-to-date because when I tried to update the firmware, the installation tool reported that there is no need of an update.
I tried also the default BIOS settings and also change the only parameter it may be relevant for video in BIOS: something about video mode (from Auto to PCI Express (PGA) or something).
A wierd thing is that also in BIOS in the menu where the PCi configuration is shown (can't be modified) besides the unpopulated PCI slots it says that the only populated PCI slot (the 16x one I expect) runs or it's configured at 8x. Maybe this detail helps.
Unfortunately I couldn't find any information about motherboard/bios settings/jumpers that may modify the PCI-e working mode.
MB: Intel DP55WG
Proc: Intel i3 530
Memory: 1x2G Corsair 1333MHz, DDR3 (the second module it's broken, so memory needs replacement)
Power: CoolerMaster GX 550W
Video: Gainward Geforce GTX460 768MB
HDD: Samsung Spinpoint F3 500GB
OS: Windows 7 64bit Professional
I use the latest drivers for MB and Video, BIOS updated to the latest version, and the video card is powered from the PSU by two 6pin connectors.