PCIEx16 problem , PCIEx8 all ok

[Rart]

Hello

Intel I7-4790K
Asus Maximus VII Ranger
Gigabyte GTX 960 Windforce 2x oc
Power Corsair CS750M
G-skil 8 Gbs ram (2x4Gbs)

My new pc has a problem since i build it , it works fine using windows 7 (folders , pictures) and on the internet and watching videos .
But running a more demanding 3d game or benchmark the nvidia driver crash (nvidia Display driver stopped responding and has recovered) after some seconds ,
for example on Valley Benchmark 1.0 ,Heaven Benchmark 4.0 ,3DMark ,3DMark 11 and others .

Did many test without luck :
Instaled all nvidia drivers (using Display Driver Uninstaller before install the new drivers) .
Installed chipset update, sound update, Intel(R) Management Engine Interface update (<<this is needed???) , AMDA00_Win7-8-8-1_V1010 something about USB's , so that all the device manager can be without the yelow interrogation simbols "?"
Did CPU stress test with IntelBurnTest 2.54 , all ok .
Did a memory test with memtest86+-4.20 3 pass's , all ok .
Did 3 motherboard bios updates .
Tried 2 screens , 1 dvi-i to dvi-i , 1 dvi-d to hdmi
Tried hdmi to hdmi but i get a very red screen and a look of just 256 colors in windows , i will talk about this later<<<<<
Tried many diferent setting in the bios , UEFI .
And alot more things that i dont remember now...

After alot of tests , changes , updates :
i have found that this problem happens with the card installed in the PCIEx16 slot ,
But works ok if its in the PCIEx8 .
In the PCIEx8 works very well , theres no nvidia driver crashs , theres good fps on Valley and heavean (the tests i use more) .


After all this , whats the problem ?
Motherboard PCIEx16 slot Faulty ?
CPU is Faulty ?
(i read somewere that the CPU controls the PCIEx16 lane . About the x8 lane ,the CPU doesnt control the PCIEx8 lane or it does ? )
Video Card is Faulty ?
Is possible that a video card it self works ok in the PCIEx8 slot but dont work in the PCIEx16 slot ? (because its somehow damaged using x16 "system" ? )

I tested a old card(7900GS) in the PCIEx16 slot and works without crashs but that card is not so demanding as a GTX 960 tho
(The 7900GS i tried it in the Valley test but the fps were very low , but the driver didnt crashed. I need try it again but in the game LFS for example to see if crashs or not)

Any other tests i should do ?
What you guys think about this?

Thanks

My other topics just in case it helps too:
http://forums.guru3d.com/showthread.php?p=5052164
http://www.tomshardware.co.uk/answers/id-2612156/pciex16-crash-problem-pciex8.html
https://rog.asus.com/forum/showthread.php?60375-PCIEx16-3D-crash-problem-PCIEx8-3D-all-Ok
https://forums.geforce.com/default/topic/826208/geforce-drivers/pciex16-3d-crash-problem-pciex8-3d-all-ok/

[Rart]

Case closed and Solved .
Faulty Gigabyte GTX 960 Windforce 2x oc .

Got a new Gigabyte GTX 1070 G1 Gaming 8G and works great at the pci-express x16 slot .

The difference is huge in terms of fps , in the Valley Benchmark at the start (first frames\scenario), the GTX 960 gets 64 fps max (both AA off) and the GTX 1070 gets 170 .

[AgentFXA]

I had a similar problem with my AMD box and a 380 card - after a game crash (BS) the vcard was on x 1 or x8 level after reboot.

To keep x16 mode stable your power connection to the card has to be flawless. For me it was a flaky connector/plug issue once fixed my card stays x16 mode even after a rare crash.