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AHein14
Beginner
4,004 Views

HD Graphics 620 and displayport MST

Hi,

 

 

I have an interesting issue. As my work laptop I have a Dell Latitude 5480 with Intel HD Graphics 520. I use with Dell WD15 USB-C dock and two monitors, first one being 2560x1440 resolution (MST) and second 1920x1080.

 

With my work laptop everything works fine and both displays have a pleasant 60 Hz refresh rate. However, my personal laptop is a Dell Latitude 7480 with Intel HD Graphics 620. When I plug the same dock in it, I can only get a max resolution of 1024x768 on the second monitor (without lowering the first display's resolution).

 

I've updated the display drivers and the laptop BIOS, dock firmware, everything. But nothing seems to make the 7480 work like my work laptop does, given it has an earlier model of the HD Graphics.

 

It seems like there's a bug somewhere. Does anyone have any ideas what could cause this issue?

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8 Replies
Wanner_G_Intel
Moderator
3,239 Views

Hello AHein14, 

 

Thank you for submitting your question on this Intel® Community.

 

To better assist you, we would like to gather more information about your system configuration. With both external monitors connected to your computer (Dell* Latitude 7480) Please generate the following reports:

 

  • DxDiag*
  1. Go to Start > Run or Windows Key + R.
  2. On the Run prompt, type "dxdiag" then click OK.
  3. On the DirectX Diagnostic Tool window, click on Save All Information.
  4. Browse to a folder, type in a filename then click Save.

 

  • Graphics report
  1. Open the Intel® Graphics Control Panel.
  2. Click on "Options and Support".
  3. On the "Information Center" tab, click on "Save" and choose a location on your computer to save the report.

 

  • Please describe how the monitors are connected to the Dell* Dock WD15 (HDMI*, mDP*, VGA, adapter, etc.)
  • Provide the model numbers for both monitors.

 

Wanner G.

Intel Customer Support Technician

A Contingent Worker at Intel

AHein14
Beginner
3,239 Views

Hello,

 

Here are the reports (DxDiag)

AHein14
Beginner
3,239 Views

And Graphics Control Panel report.

 

The monitors are connected via mDP, first to Dell U2515H and then daisy chained to HP EliteDisplay E221c.

Wanner_G_Intel
Moderator
3,239 Views

Hello AHein14, 

 

If you need further assistance, please let us know. We will be glad to assist you.

 

Wanner G.

Intel Customer Support Technician

A Contingent Worker at Intel

Wanner_G_Intel
Moderator
3,239 Views

Hello AHein14, 

 

Thank you for your response.

 

We will review the reports attached and update this thread soon.

 

Wanner G.

Intel Customer Support Technician

A Contingent Worker at Intel

Wanner_G_Intel
Moderator
3,239 Views

Hello AHein14,

 

Thank you for your response.

 

Based on the reports attached and and maximum resolutions supported by the Dell WD15 USB-C dock, it seems that you are unable to set 1920 x 1080(p) (60.000Hz) on the second monitor due to the bandwidth needed to support dual display configurations.

 

  • The maximum resolution supported by the dock is either 3840 x 2160 @30 Hz or 2560 x 1600 @60Hz.

 

Source: Dell Dock WD15 (USB Type-C) Information, Compatibility and Specifications

 

  1. To configure 3840 x 2160 @ 30 Hz, the bandwidth needed is: 7.46 Gbps approximately.
  2. To configure 2560 x 1600 @ 60Hz, the bandwidth needed is: 7.37 Gbps approximately.

 

By design, bandwidth is usually shared among the devices connected to a computer or dock, limiting the number of displays you can connect to the dock/computer at the same time and the resolutions you can use. Since this is defined by industry standards, our recommendation is that you contact your Original Equipment Manufacturer (OEM) to obtain accurate information about the standards used by the computer/dock.

 

In addition, please take a look at the approximate bandwidth needed to use these configurations:

 

Monitor 1 > 2560* 1440 @60 Hz = 6.64 Gbps

Monitor 2 > 1280* 720 @50 Hz = 1.38 Gbps

Total Bandwidth: 8.02 Gbps

 

This may explain why you cannot set higher resolutions on the Dell Latitude 5480.

 

Note: Information taken from the reports.

 

What we can recommend in this scenario is that you use lower resolutions or refresh rates in order to obtain 1920 x 1080p at 60Hz on your second monitor.

You may also refer to the "Resolution Support Table" on the Dock specifications site for Dual Display configuration.

 

It is worth mentioning that to compare two or more systems, you may need to review the product specifications to understand the bandwidth limitations for different video outputs on different systems.

 

Wanner G.

Intel Customer Support Technician

A Contingent Worker at Intel

Wanner_G_Intel
Moderator
3,239 Views

Hello AHein14,

 

Were you able to review the recommendations provided? 

If you need further assistance, please let us know.

 

Wanner G.

Intel Customer Support Technician

A Contingent Worker at Intel

Wanner_G_Intel
Moderator
3,239 Views

Hello AHein14,

 

We have not heard back from you, so we will close this inquiry. If you need further assistance, please post a new question.

 

Wanner G.

Intel Customer Support Technician

A Contingent Worker at Intel

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