I just got a Gigabyte G1 GTX 970 card, to replace my GTX 670's in SLI, however I wish to keep one 670 to use as a dedicated PhysX card however I've run into some problems. I have an ASUS P9x79 Pro motherboard, running Windows 10

Both cards are slotted in, 670 in the slot nearest the CPU, G1 below it both are in the blue PCI-E slots. Boot up with a DVI cable in the 970, but nothing shows on the screen, no POST screens etc and I get the "monitor going to sleep". There is a permanent red LED for "BOOT_DEVICE_LED" on the motherboard at this time. I then plug the same DVI cable into my 670, and the screen powers on fine, the LED has now gone out... I then boot to Windows.

Once booted to desktop I switch DVI cable back to the 970, and it works fine, picture, resolution etc all ok. I then restart the machine with the DVI in the 970, same thing happens, no picture until I switch back to the 670.

  • I have switched both cards around, 970 on top, 670 in 2nd, same thing happens.
  • I have dedicated the 670 as PhysX card via the nVidia control panel
  • Both cards work by themselves, but problems start when 2 are connected into the mobo
  • Both cards also work simultaneously (in Windows) with a monitor working when plugged in each
  • SLI bridge has been removed

Any ideas?

  • Is there any place in the firmware (EFI) to set a primary display? – Hennes Dec 8 '15 at 9:40
  • Usually the first slot closests to the cpu is the primary (for the bios/Uefi) haveing it plugged with a DVI should have it show, your indicating that either your trying to use a reverse method (primary in the other slot done for better cooling), or it is crazily reversed for what is "normal". Things you might try, any adjustment in the bios for which is primary (only some bioses) any adjustment for the PEG over the INtegrated, Testing with the Integrated (on-die) GPU on , or off, which may change the results. – Psycogeek Dec 8 '15 at 9:55
  • Just switched the cards over again, G1 970 now in slot 1 closest to CPU, 670 below it. Same thing happens, no picture on boot up with DVI in the 970, i have also tried other connectors, HDMI and Display Port, same thing happens. Works fine when I swap it over to the 670. Just launched into Windows, and now nVidai control panel cannot even see the 970 – jerrythebum Dec 8 '15 at 10:31

So it now works.... I reseated multiple times, as I had done before, changing something ever so slightly every time and eventually it worked. Don't ask why, I have no idea. What I changed this time tho? The levers that hold the PCI cards in tight.

case levers Case Levers
original link to high res pic http://imgur.com/lxFuPgw

Levers 2 and 3 hold in the 970, see they are not flush with the other levers and pushed all the way in, but the ones holding the 670 are? No idea why this affected it, perhaps due to putting too much pressure against the mobo PCI pins or something... who knows, but it works (for now)

Cheers guys.

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