External monitor does not display BIOS or pre boot

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  1. Posts : 162
    Windows 10x64 Pro
       #1

    External monitor does not display BIOS or pre boot


    Hi, I have a Dell XPS 17 9710 connected to a Dell UP2720Q external monitor via a Thunderbolt cable. The XPS remains powered on with the lid closed and with the UP2720Q displaying Windows. The issue is that whenever I boot the monitor does not detect a thunderbolt signal coming from the XPS and briefly enters standby mode until Windows desktop shows up without porblems. So whenever I need to enter BIOS or any other pre Windows activity (booting from an external USB drive), I am forced to use the XPS internal display. Is there a way to have the external monitor pick up the thunderbolt signal at all times during boot? I explored BIOS setting and enabled an option called "Allow thunderbolt boot devices" or something like that without success. Thanks
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  2. Berton's Avatar
    Posts : 12,259
    Win10 Version 21H2 Pro and Home, Win11 Pro
       #2

    More for an example than a solution but most BIOSes will have USB 2 support but have to wait until the OS loads the drivers for USB 3. Based upon the description it's quite possible you are seeing the same type of issue.
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  3. Posts : 162
    Windows 10x64 Pro
    Thread Starter
       #3

    Yes, the thunderbolt drivers are not being loaded during POST. I found a setting in BIOS that says like "enable direct Thunderbolt in BIOS" or something like that, I enabled it without success.
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  4. sygnus21's Avatar
    Posts : 5,752
    Win 10 Pro (x64) 21H1 (19043.1023
       #4

    In keeping things simple, and not claiming to be the master expert here....

    antares said:
    Hi, I have a Dell XPS 17 9710 connected to a Dell UP2720Q external monitor via a Thunderbolt cable. The XPS remains powered on with the lid closed and with the UP2720Q displaying Windows. The issue is that whenever I boot (I assume you mean reboot the PC) the monitor does not detect a thunderbolt signal coming from the XPS and briefly enters standby mode until Windows desktop shows up without porblems.
    Be aware anytime you reboot, you basically power off the machine. That mean everything loses power, including all ports. With that, it's no surprise you're experiencing what you see. And yes, changing that BIOS setting doesn't change the whole power off thing when rebooting. In short, this is normal behavior.

    antares said:
    So whenever I need to enter BIOS or any other pre Windows activity (booting from an external USB drive), I am forced to use the XPS internal display. Is there a way to have the external monitor pick up the thunderbolt signal at all times during boot? I explored BIOS setting and enabled an option called "Allow thunderbolt boot devices" or something like that without success. Thanks
    Again, nothing new as the system now has to reinitialize ports. Here, it sounds like the Thunderbolt port my not fully initialize until the BIOS posts (and possibly only after entering Windows). So, in answering the bolded question... if that BIOS setting you toyed with doesn't work, then I'm afraid the answer is most likely no.

    Also, the reason the "laptop" screen still works is because it's not connected to any "USB/Thunderbolt ports", but rather the built in GPU (whether on the CPU or off a dedicated GPU) which initializes immediately during post.

    antares said:
    Yes, the thunderbolt drivers are not being loaded during POST. I found a setting in BIOS that says like "enable direct Thunderbolt in BIOS" or something like that, I enabled it without success.
    Again, (when rebooting) once the system powers down, there is no electrical signal to output any video. And even when the system reboots, now that port needs to be initialized (most likely when you fully enter Windows as you've seen).
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  5. Posts : 162
    Windows 10x64 Pro
    Thread Starter
       #5

    Thanks sygnus for your detailed reply. Let me clarify some points here to clear any dust:
    1) When REBOOTING (boot=reboot) yes, there is an instant of maybe a few milliseconds during which no power is being delivered, not even to the internal laptop display. During this instant it is normal that both the internal display and any external display appears black
    2) As soon as the Dell logo shows up in the laptop's internal display the POST (pre windows) stage begins. It is during this POST process (where eventually by pressing F12 you can enter BIOS, or pressing F8 you can enter the boot menu) that the external thunderbolt monitor DOES NOT receive any signal from the laptop, hence displaying a black screen and a message saying "no thunderbolt detected, entering standby mode". THIS IS THE ISSUE I'M TRYING TO FIX, because things as they are if I want to see the BIOS menu or any POST process I have to open de laptop's lid and check POST from the laptop's internal display, which is very inconvenient.
    3) Eventually once Windows loads the external monitor displays the normal windows desktop, no problem here.
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  6. steve108's Avatar
    Posts : 18,990
    19041.1466 - 2004/20H1 Pro x64
       #6
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  7. Posts : 162
    Windows 10x64 Pro
    Thread Starter
       #7

    Thanks Steve, many options to explore there, but most of them resort to the external keyboard which in my case it's also connected to thunderbolt (the XPS 9710 only has thunderbolt ports, no USB2), so if there's no signal coming out of the thunderbolt ports during POST both the monitor AND the external keyboard are affected. As I see it, the only solution would be at the BIOS firmware, to have a setting that unlocks thunderbolt during POST
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  8. Ghot's Avatar
    Posts : 15,798
    Win 10 Home 10.0.19044.1469 (x64) [21H2]
       #8

    antares said:
    Thanks Steve, many options to explore there, but most of them resort to the external keyboard which in my case it's also connected to thunderbolt (the XPS 9710 only has thunderbolt ports, no USB2), so if there's no signal coming out of the thunderbolt ports during POST both the monitor AND the external keyboard are affected. As I see it, the only solution would be at the BIOS firmware, to have a setting that unlocks thunderbolt during POST


    In my ElevenForum post about certain ports having different priorities... when I was troubleshooting that, EVGA explained, that at least in the case of discreet video cards... the port priority was set in the video card BIOS, not in the motherboard BIOS.
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  9. Posts : 162
    Windows 10x64 Pro
    Thread Starter
       #9

    Ghot said:
    In my ElevenForum post about certain ports having different priorities... when I was troubleshooting that, EVGA explained, that at least in the case of discreet video cards... the port priority was set in the video card BIOS, not in the motherboard BIOS.
    AFAIK there is no way to enter the Nvdia RTX3060 BIOS in the XPS 9710
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  10. Ghot's Avatar
    Posts : 15,798
    Win 10 Home 10.0.19044.1469 (x64) [21H2]
       #10

    antares said:
    AFAIK there is no way to enter the Nvdia RTX3060 BIOS in the XPS 9710
    I realize that. I just wanted to point out that there probably ISN'T a setting in the motherboard BIOS for this issue.
    Someone in the ElevenForums topic, mentioned that the TB ports on the left side, are the ones you should use??

    As I mentioned... I would try each of the four TB ports, after shutting the laptop OFF, in between changing ports.
    Otherwise... I would just call DELL tech support.

    Especially since both the laptop and the monitor are... DELL.
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