Dual GPU not working on x399 Taichi

Edited by noktek - 18 Nov 2017 at 6:34pm

noktek, first, please post your system specifications, including the versions of OS and BIOS and power supply - I suggest in your signature as I have.  As daddyo said, power is very important.  Plugging in the MB PCIe power cable when it is not needed definitely should not prevent the system from powering up.  I connected mine just to have a place to park the connector - no problem.  Make sure you are using the PCIe power cables not the CPU cables for the video cards and the MB PCIe connector.  I have never tried multiple video cards, so I have some questions.  Is it OK to use different model cards?  Have you connected the bridge connector(s) between the two cards?  Please tell us what PCIE slots you are using.  Enjoy, John.

hi guys thanks for all the suggestions, it was a hard day of trial and error and nothing accomplished:

noktek, I think you need more power, perhaps 1000 Watts.  Hopefully others will comment.  I have 850 W with one video card and a lot less storage.  The CPU can use close to 200 W under load.  I assume drives are TB (Terra Bytes).  Can you borrow a heftier power supply to try or return yours for credit?  If you test with more power and still have problems, then perhaps you have a MB problem and need to talk to ASRock.  I get drivers from only the vendor who makes the product, not other sites.  Have you looked here: http://www.nvidia.com/Download/Find.aspx
Enjoy, John.

An HX 1200i should be enough for a TR system and two video cards. This PSU's +12V rail is capable of 100A output. If the PC is drawing over 100A from the +12V rail just booting and at idle, so much for power efficiency of TR:

http://www.corsair.com/en-us/hxi-series-hx1200i-high-performance-atx-power-supply-1200-watt-80-plus-platinum-certified-psu

Switching to single rail will skip the need to balance the power on the +12V rails, but just starting and running the PC should not cause that much of a power draw. 40A on a rail might be a limitation for the CPU, which could interfere with the PCIe lanes, just a thought. But the CPU here has multiple power sources/connections.

I would start over by clearing the CMOS/UEFI, connect all the PSU cables to the board as required, and use one video card. Possibly starting with the 780 alone in the board. Once one card is working normally, add the other. If you've never tried the 780 by itself, that's what I would try now.

I'm wondering if the VBIOS in the 780 SC is UEFI/GOP compatible. It should be if it is an EVGA video card, EVGA went to UEFI compatible VBIOS starting with the 700 series. The 1080Ti will have a UEFI/GOP compatible VBIOS. Since you use a 960 Pro NVMe SSD as the OS drive, the Windows 10 installation should be UEFI booting by default. Windows 10 installed via a USB flash drive?

You lost me on "If i remove uninstall the 780 it then shows up as VGA adapter displaying no errors." That's the Device Manager entry, correct? I assume that is before you restarted the PC? Or does that ghost entry remain after a restart?

I wonder if this issue is related to the early Window 10 RS1 versions and the IOMMU option being enabled, not being compatible. Obviously the Windows 10 installation boots, so you are either using a Windows 10 RS2 version, or have IOMMU disabled.

So the driver version is identical for both video cards? During the installation, are you prompted to select which card is the target of the installation? Or do both cards just get the driver installed? No errors from the installer during or after the driver installation process?

What happens if you run the NVIDIA Control Panel software with both cards in the PC? Can you check how many PCIe lanes are being used by the 780 with that or other software? If you've used two different video cards like this in the past, is there anything you've had to do to get them working?

Usually two video cards don't have a problem with the amount of memory Windows needs to deal with both cards. The UEFI option to change that is usually called Top Of Lower Usable Dram, or TOLUD, setting it to Dynamic. If and where that option is in your board's UEFI, I'm not sure, usually in the Chipset Configuration screen, but could be elsewhere with X399.

Try to keep an open mind about the mother board being the problem. We see that being blamed for issues all the time, and when a new board fixes nothing, which we also see all too often, it's more than just a waste of time.