Dell 5400 8th Gen i7 won't output 3 external monitors @ 1080p

Nitrousbird

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Latitue 5400, 16GB RAM, i7-8665U (8th Gen). Connected to a Dell WD19 Thunderbolt hub via the only USB-C connector on the laptop, utilizing the i7 integrated graphics. I realize it is only 3-display capable.

Three external monitors, all 1080p. Two using DP and one HDMI. The laptop will output to two @ 1080p plus its built-in monitor @ 1080p. If you try the three externals, it will lower the resolution to one. If you try some trickery in Intel Graphics Command Center, I have got all three to 1080p once, but the video quality was awful on one of the monitors.

It is not anything external of the laptop. Taking the same USB-C (Thunderbolt) connection and plugging it into my Surface Pro 7 (10th Gen i5), all three externals work perfectly. I've also tried it with all three monitor connections directly to the WD19 and running all three to a single DP port via a DP 1.4 MTB hub (which is my main use case, as I move the single display port connector over to my iRacing desktop with a GTX 1060 that has no issues pushing triple 1080p through it).

I'm running out of ideas. The Dell has all Windows 10 updates and the latest drivers. I just can't figure out why it can't push triple 1080p externally but yet can process two external and one internal just fine.
 

Eximo

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USB 3.1 Gen 2 (10Gbps) according to Dell. Thunderbolt 3 is an option you may not have.

8bit 1080p 60hz is 3.2Gbps, 3 would be just under 10Gbps, plus I'm sure there are USB ports, ethernet, audio, etc on there as well.

Being directly connected to the GPU is going to certainly help out the internal display, won't use USB at all.
 

Nitrousbird

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USB 3.1 Gen 2 (10Gbps) according to Dell. Thunderbolt 3 is an option you may not have.

8bit 1080p 60hz is 3.2Gbps, 3 would be just under 10Gbps, plus I'm sure there are USB ports, ethernet, audio, etc on there as well.

Being directly connected to the GPU is going to certainly help out the internal display, won't use USB at all.
Why do you think it works with my Surface Pro 7 just fine on the same connection, but not on this Dell Latitude 5400? Digging further, it does look like my WD19 is a non-Thunderbolt version of the dock. But that still doesn't change the issue with it working on the Surface but not the Dell. The only thing plugged into the Dell that is difference is the Unifying receiver for my Logitech mouse - all other connections are at the dock, which both the Surface and Dell would see.

Further, I experimented by moving the HDMI cable from the dock directly to the laptop, so the USB-C only had to feed two monitors. Same result - two of the monitors look great, the 3rd looks awful. It's always whatever is considered the 3rd (last connected) monitor that looks bad.
 
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Eximo

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Surface Pro 7, not sure on its details. Microsoft isn't very forthcoming, just says USB-C on their spec page. That could be any speed and capability at this point.

As for your other scenario, it really depends on how the display connectors are internally connected. What most people assume is rarely the case and sometimes they will share bandwidth internally with other buses. Generally the internal display gets a direct connection, the others, it completely depends on how they designed it.

If your dock is thunderbolt and your Surface pro is too, likely a 40Gbps connection, plenty to work with. Even if it is 20Gbps, that would work too.

I'm beginning to suspect the Not sure what happened to the end of that sentence, but I also don't remember what I was going to write.
 
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Nitrousbird

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Dell support is working on this now. They keep trying to find excuses around the problem, but keep getting stumped when I point out that I only have two DP's attached to the WD19 and the 3rd HDMI attached directly to the laptop with the internal display disabled. Can't blame the USB-C port with only two displays attached to it...
 

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