Question [Solved] Plug in the only monitor to the second GPU but it won't light up until entering Windows 10

Apr 25, 2019
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Hi,
I have a wired situation and wanna some help to understand what happened from you experienced experts here. I have assembled a new PC on ASUS Prime X299 Deluxe II with both GT1030 in slot 1 and TITAN RTX in slot 2 (my CPU supports up to 44 PCIE lanes). During the first time starting the PC and installing Windows, the only monitor was connected to GT1030 via HDMI. Things turned out smoothly.

Yesterday, I switched the only monitor to RTX TITAN. When I booted, the screen didn't light up for a while. When it finally lighted up, it was already showing the login page of Windows 10. So I missed the whole POST screen. The RTX works fine, as it passed stress test.

And if I booted with GT1030 connected to monitor, I can see both POST and Windows screen. And if I switched monitor from GT to RTX after entering Windows, it also switches smoothly.

I want to understand why the RTX has no output during POST:
  1. Is it because RTX is in the second slot? I cannot put it in slot 1 as the backplate touches CPU heatsink. GT1030 is low profile card and can sit nicely there.
  2. Is it because the BIOS or UEFI record GT1030 for display output during the first time booting, so the system only looks for monitor on GT1030?
  3. Can I somehow make the PC to automatically figure out the display regardless which GPU the monitor is connected to, so that I can see the POST screen?
Thanks a lot.

UPDATE: It's solved by disabling CSM under Boot options in BIOS, to enforce UEFI boot. With that said, the OS should be installed in UEFI mode (e.g. GPT partition for Windows 10 disk).
 
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Probably a combination of 1 and 2. Graphics cards cycle through the display outputs. BIOS shows in the display connected to the output with the highest priority. (I found this out after contacting my graphics card manufacturer about BIOS showing on a secondary display rather than my primary display.)

In your case, I would suspect the PCIe slots are also prioritised as well. The main solution would be for the Titan to be installed in the first PCIe slot, but as you've mentioned there's a physical limitation for your hardware. Is there any particular reason you need the GT 1030 installed? Removing it and only using the RTX Titan would seem to be the only real solution.
 
Apr 25, 2019
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Probably a combination of 1 and 2. Graphics cards cycle through the display outputs. BIOS shows in the display connected to the output with the highest priority. (I found this out after contacting my graphics card manufacturer about BIOS showing on a secondary display rather than my primary display.)

In your case, I would suspect the PCIe slots are also prioritised as well. The main solution would be for the Titan to be installed in the first PCIe slot, but as you've mentioned there's a physical limitation for your hardware. Is there any particular reason you need the GT 1030 installed? Removing it and only using the RTX Titan would seem to be the only real solution.
Thank you Obakasama. That is what I thought as well.

In my case, I need a separate GPU for display, so that the memory of RTX can be fully utilized for deep learning model. And I have to clarify myself. The RTX actually can be physically installed into slot 1, although it almost touches CPU heatsink. But this orientation is not thermal optimal for the RTX, when I tested RTX in slot 1 and GT in slot2.

The monitor would always be connected to GT1030 in my "normal" situation. I just found this problem coincidentally and what to understand what happened.

I'll play with some BIOS settings, like turning off "fast boot", when I'm beside that PC. I'll stay with what it is if nothing works. At least I can do the monitor switch inside the operation system if I really have to.
 
Apr 25, 2019
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Another member mentioned something like a 'PCIe lane simulator'. Not sure if anything like that is applicable here (or if it even has any relevance).
Hi Obakasama, finally I figured it out.
In the Bios, I disabled CSM (Compatibility Support Module) under Boot options. This ensures the system boots purely using UEFI instead of the mix of legacy BIOS and UEFI. During the pure UEFI boot, monitor will light up during POST regardless which GPU it's connected to. Of course, that requires an OS installed through UEFI.
Thank you for your answer. It inspires me to find the solution.
 

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