GPU not detected on 3 diferent Dell Optiplex 790 SFF

[Edanhice116]

i'm well aware of the pci-e power limitation, i've read a lot about it in the forum, but, since the power connector on the motherboard is the regular ATX connector i'd said "screw the case, i'll make one later" and decided to use a ATX power supply (650w) and it worked really well with the mobo as it is, the problems start when I tried to add a GPU, and NVIDIA GTX 660 on the PCI-e x16 port, the mobo doesn't detect it at all (it does starts using the iGPU but neither windows nor the bios detect the card in the pci-e)

later, for science, i tried the next port (wired PCI-e x4 said the manual) and the mobo detected the GPU and worked really well for days with any game i tried to run.

at first I thought it was a bios limitation, like "you can only put this, this and that gpu models on this PC" as i tried a low profile nvidia GT 8400, nv gt 6200, ati x300 and ati x1500, and non of them worked on the PCI-e x16, but if i connected any of them on the PCI-e x4 they all work flawlessly

this was the same with the 3 optiplex 790 sff i'm testing, so, either that or is a weird "the 3 have faulty PCI-e x16 ports" or i'm doing something wrong, any ideas??

 

[Lutfij]

1| Can you please state the PSU you're using? On that note can you please state your full system's specs inclusive of OS?
2| Have you made sure your BIOS is up to date?
3| On all three models did you use the (unnamed)PSU you stated above to power your entire system?
4| Try taking an eraser and clean the PCI-E contacts on your GPU by slightly running the eraser along the length of the PCI-E gold connector.
5| Are all the cards(outside of the GTX660) you've tried low profile cards?

 

[Edanhice116]

1) First it was my Thermaltake SP-650P, later I borrowed a Corsair CX650M, same result

My system specs:
Core i3 2100@3.1Ghz
Chipset Q65 Express (MOBO Model 0D28YY)
2x SATA II 2.5" Toshiba 7200 rpm 250GB
8 GB RAM (2x ADATA XPG DDR3 1600MHz)

The other two are identical except for the ram and hdd

2) in my system, yes is up to date, the other two aren't
3) yes the whole system, I tried the 3 with the thermaltake and then again with the corsair (actually did a lot of testing)
4) did that after the first fail (plus the GTX 660 was working on another PC)
5) yes, all low profile cards