HELP: Computer doesn't boot at all after replacing DVI monitors with DisplayPort monitors

[Zachary Parker]

My equipment:

• 
  ■ Motherboard: Gigabyte Z170X Gaming 3
  ■ GPU: MSI R9 390 Gaming 8G (2 DVI-D ports, 1 HDMI, 1 DisplayPort)
  (Here's a link to the full build)
  ■ Old monitors: Two Dell SE198WFP (DVI monitor) and one Asus VE247H (DVI monitor on DisplayPort through an adapter)
  ■ New monitors: Three Dell U2414H (DisplayPort monitors, daisy-chainable)

So, last night I had my new monitors delivered and tore down my old ones. I started by plugging in one of the new monitors through the DisplayPort and tried to turn the computer on, but all I got was a Black Screen. Read further down for a description of this behavior.
So the next thing I tried was to plug one of my old monitors back in through a DVI port, while keeping the new monitor plugged in as well. This allowed the computer to bootup, and it even recognized the new monitor. I then proceeded to hook up the second new monitor into the first, and plug the third into the second. Each monitor is recognized by the computer. Everything's working great so far. I unplug the DVI monitor, and the computer still works. I have a working computer and all three of my new monitors are gorgeous. I play The Division for several hours, everything's perfect. Until I shut the computer down and try to boot it up again. Now I've got the Black Screen again, on all three new monitors.
Time to plug in one of my old monitors again. And again, the computer boots without a hitch. So there's my problem: The computer will not boot unless something is plugged into DVI.

The Black Screen

• 
  ■ When I press the power button to turn the computer on, the case fans and LEDs turn on, the monitor(s) awaken from standby, and the monitor backlight comes on, but there is only black on the screen. No POST, nothing.
  ■ The backlit keyboard, which usually comes on within a second or two of pressing the power button, doesn't light up.
  ■ Nothing else happens. I waited up to 10 minutes but there was no change.
  ■ Pressing the power button again results in an instant power off of the fans, which wouldn't happen if the computer was booting properly.

This suggests to me that the computer cannot find a connected display during initial boot, and refuses to continue without one. For some reason, it seems to be only checking the DVI ports for monitor presence, and not the rest of them.

A side note: When I was running on my old monitors, the POST and BIOS screens would appear on both the left monitor (DVI) and the center monitor (DVI via DisplayPort). Now, those screens only appear on the DVI monitor, and not any of the new ones.

Another side note: I previously noted this behavior in my computer awhile back when I tried to hook it up to a TV through the HDMI. It wouldn't boot then either. I wasn't too concerned about it at the time, and just switched to a DVI monitor. HDMI does work as a second monitor when there's a DVI present.

The way I see it, I have several options:

• 
  ■ Keep one of my old monitors hooked up under my desk, which I won't use except to access BIOS when needed (This is what I'm doing right now. It's not ideal, but it works)
  ■ Keep one of the old monitors hooked up and actually use it as a 4th display (requires spending more money on a larger desk and/or a VESA monitor stand)
  ■ Create some kind of dummy plug for the DVI port so the computer thinks a monitor is connected there (inadvisable, no way to use BIOS menu)
  ■ Get a converter so I can plug one of the new monitors into the DVI port (Requires spending more money)
  ■ Return the new monitors and go back to my old ones (unlikely)
  ■ Identify and fix the problem (This is where you come in!)

 

[AdmiralDonut]

Whether a display is connected or not is irrelevant, the computer will still boot. That suggests an issue with either the motherboard or the GPU.

 

[Zachary Parker]

Whether a display is connected or not is irrelevant, the computer will still boot. That suggests an issue with either the motherboard or the GPU.

I agree it must probably be a problem with the motherboard or the GPU, but what sort of problem would cause the computer to boot fine with a DVI connected and not without one?

 

[Zachary Parker]

Someone suggested I go into BIOS and disable the CSM (Compatibility Support Module). Well, I did that (and had to change another option from "Other OS" to "Windows 8/10" in order to do so) then I restarted the computer... Well, the new DisplayPort monitors turned on this time and I got a picture on them, but...

This is what I got instead of the normal POST screen. Again, the computer shut off immediately when I pressed the power button.
I was able to get back into the BIOS and revert the changes only by unplugging the DisplayPort monitors and plugging the DVI one back in. Computer is once again back to "normal" after reverting the changes.

 

[AdmiralDonut]

First thing I'd do is try the monitors with another card, if at all possible. Second would be to try the card in another machine. That then rules out the motherboard and the monitors as the source of the fault.

 

[Zachary Parker]

First thing I'd do is try the monitors with another card, if at all possible. Second would be to try the card in another machine. That then rules out the motherboard and the monitors as the source of the fault.

I do have another card I can try, actually (an R7 260). I'm also considering upgrading the BIOS to the latest version, as it seems part of the "Windows 8/10" CSM component may be corrupted.

 

[Zachary Parker]

I haven't yet had the time to pull the video card out and try my other one, but I tried plugging in nothing but my DVI monitor through the DisplayPort adapter. It was able to get into the BIOS just fine. This is with the CSM ON, which means the new monitors would be getting the black screen, not the junk screen.

So it seems there's nothing wrong with the physical DisplayPort on the card during boot. The theory about the card only scanning the physical DVI port seems wrong.

New theories:
-The BIOS assumes DVI signal for some reason and only outputs that signal on boot.
-On boot, the BIOS tries to read the EDID information from the new monitor(s) and either can't output a resolution and refresh rate that's compatible, or the BIOS somehow crashes/freezes while trying to read the EDID. Not sure if that'd be a fault of the monitor or the BIOS. In any case it seems Windows can read the EDID well enough to display everything correctly AFTER booting up.

 

[AdmiralDonut]

I haven't yet had the time to pull the video card out and try my other one, but I tried plugging in nothing but my DVI monitor through the DisplayPort adapter. It was able to get into the BIOS just fine. This is with the CSM ON, which means the new monitors would be getting the black screen, not the junk screen.

So it seems there's nothing wrong with the physical DisplayPort on the card during boot. The theory about the card only scanning the physical DVI port seems wrong.

New theories:
-The BIOS assumes DVI signal for some reason and only outputs that signal on boot.
-On boot, the BIOS tries to read the EDID information from the new monitor(s) and either can't output a resolution and refresh rate that's compatible, or the BIOS somehow crashes/freezes while trying to read the EDID. Not sure if that'd be a fault of the monitor or the BIOS. In any case it seems Windows can read the EDID well enough to display everything correctly AFTER booting up.

Your EDID theory certainly sounds right. Have you contacted your motherboard manufacturer to see if there is something they can do?

 

[Zachary Parker]

...Well, I really wish I knew what the problem was, but in any case, it appears to have gone away. After two weeks of trying different things, this is what apparently solved my issue. I feel like an idiot for not trying this first.

What I did:

Thinking it may have been a problem with one of the DisplayPort cables, I asked a friend if I could borrow one of their cables. I disconnected all of my monitor cables (including the USB cables for the monitors' USB hubs) and tried plugging one monitor (the same one that has always been first in the chain) to the computer with the new cable and booting it. But I just got the black screen again.

Next, I tried plugging in a different monitor with the new cable. This time, the computer booted up! It was the first time I had ever seen a correct POST screen on any of my new monitors. So then I was thinking there might be something wrong with that one monitor I had been using as first in the chain.

After that, I tried switching to the third monitor to see if it would work as the only monitor, and it did. Then I tried switching back to the original monitor to verify it still was the problem... And it also worked.

Next, I tried switching back to the cables that came with the monitors. With one monitor plugged in, the computer booted fine. Then with the computer running, I proceeded to daisy chain in the second monitor, and the third, and Windows recognized each one. Then the big test... I shut the computer down and booted it up again, and it still booted up just fine. I've gone from being unable to solve the problem to being unable to replicate the problem.

I can only assume that somewhere, one of the cables wasn't connected properly, and just needed to be re-seated. Or maybe the USB connection had something to do with it; I haven't yet tried plugging them back in.

Strangely, the monitors now take MUCH longer (over 15 seconds) to start up when waking the computer from sleep than they did when I had the 4th monitor under the desk, but that's a minor curiosity.

 

[AdmiralDonut]

Well that was certainly a rollercoaster ride of weirdness. I'm glad it finally sorted itself out in the end though