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Beginner
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One Monitor won't display native resolution

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Hello, all...at my wit's end with this issue, hoping to find a resolution (no pun intended).

I have two Monoprice 4k monitors.   Until fairly recently, had no issue with both of them displaying in the proper (3840x2160) resolution.  One day, I unplugged my monitors to install a new monitor stand, and since that day, I can't get both to display in the proper resolution.  Only one will, and the other tops out at 1920x1080.

I am on a Lenovo T480s with the Intel UHD 620 installed.  One monitor is hooked up with a DP cable, the other HDMI (my original setup had both on DP, but have swapped cables back and forth with no luck).

I have attached the diagnostic file in case that helps.  I am going crazy trying to figure this one out, and no matter what I try, I cannot get the second monitor back to the native resolution.

Thanks in advance...

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Super User Retired Employee
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A couple comments:

  1. When you go through the process of putting in a new monitor stand, you can stress a few things (including your back; I know, I put in a dual VESA monitor stand a while back). I would suggest you try replacing the cables you were using.
  2. If backing off the Windows Update helped, I would suggest that there is a possibility that the update has snuck its way back on. It may also mean that a previous version of the Intel drivers is better suited to your configuration than is the latest.
  3. How well can you do if you lower the Refresh rate on the 4K screen to 24Hz. In theory, it should not look much worse than 30Hz did and may free up some bandwidth for the other monitor. There is no way you will get it back to 4K though.

...S

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Moderator
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Hello Dhoek23,

 

Thank you for posting on the Intel* Community forums.

 

In order to continue with the assistance, please provide me with the following information:

 

  • Provide a picture of the configuration you are using.
  • Please confirm if you are using straight connections: HDMI* to HDMI*, DisplayPort* to DisplayPort*.
  • If you connect only one display at a time are you able to set the 4K resolution?
  • You mentioned that you are currently using one HDMI* and the other DisplayPort, according to the report you are using both in DisplayPort, can you please confirm this?

 

Please run the following tool in Windows* and attach the report generated. 

  

Intel® System Support Utility (Intel® SSU) 

 

  • Intel® SSU Download
  • Open the application and click on "Scan" to see the system and device information. By default, Intel® SSU will take you to the "Summary View". 
  • Click on the menu where it says "Summary" to change to "Detailed View". 
  • To save your scan, click on "Next", then "Save". 

 

Best regards,

Maria R.

Intel Customer Support Technician

 

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Beginner
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Hi, Maria!

Yes, I am using one DP:DP and one HDMI:HDMI.  I tested both monitors using DP, and one on DP and the other on HDMI, and same result. 

I am able to get 4k in one monitor, yes.  The other one, not so much. 

It is odd that the report said I was in DP for both, as I definitely am using one HDMI and one DP.

I reran the report with the link that you provided and attached. 

When you say provide a picture, do you mean an actual photo of the connections, or a screenshot of the configurations?

 

Thank you for the reply, and I look forward to furthering the discussion to figure this out! 🙂

 

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Super User Retired Employee
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Which of the interfaces is no longer working properly? HDMI? USB-C?

How exactly are you connecting the DisplayPort monitor to the system? Is it a USB-C-to-DisplayPort cable or is there some sort of hub device that is (also) consuming the USB capability of the port?

Actually, please explain how you are using both of the USB-C ports. What exactly is connected to each?

...S

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Beginner
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Yes, I suppose that is an important clarification, thanks for asking.

The USB-C port of the Lenovo is used for a docking station, a Lenovo one. I have the laptop connected to the docking station, and the DP and HDMI ports on the docking station are connected to the monitors.

So it is Laptop on Docking Station>Docking Station Displayport to Monitor Displayport>DockingStation HDMI to Monitor HDMI. 

Hope this is what you were looking for, but happy to clarify further.

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Beginner
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One answer I missed:  Currently the Displayport is the one that isn't working correctly. The HDMI is working in 4k, but the DP is the one that won't let me select any higher resolution.

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Super User Retired Employee
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Let's analyze this. We have a DP 1.2 signal that is capable of supporting a single 4K@60Hz monitor. This DP signal is fed into a USB-C connector. If the USB-C connector is used exclusively for DP (i.e. a USB-C-to-DP dongle/cable is used), then the full signal is available to the dongle/cable and a single 4K@60Hz  monitor connection is possible. If, however, the cable is also used for USB - with, for example, a hub/dock device - half the bandwidth is lost to USB 3.x support. This means that it is only capable of supporting a single 4K@30Hz monitor.

So what are you able to support? You've never said, but it sounds like you are getting 1920x1080@60Hz? You should be able to do better. The only thing I can think of is that either (a) one of your cables is not good quality (USB-C, DP) or (b) by default, it is being configured to duplicate the laptop's screen. In this latter case, it will be limited to the capabilities of the laptop screen.

...S

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Super User Retired Employee
92 Views

Ok, after thinking about it, my conclusions above are nothing but poo...

The issue is that you have the HDMI output running 4K@30Hz and this is consuming a significant portion of the DP bandwidth available. By my calculations, only 1920x1080@30Hz would be possible from the second monitor.

Is this what you are seeing?

...S

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Beginner
86 Views

Thanks for your help, Scott.  I really appreciate it.

Yes, this is what I am seeing.  What is absolutely maddening about this is that it WAS WORKING! 🙂

I had 2160x3840 in both monitors.  I unplugged them to install a new monitor stand, and it hasn't worked right since.

I will add that I contacted Lenovo about this, and their advice was to uninstall the latest Windows update...I tried it, and to my shock, it worked!  For about 2 days.  Then it went back.  I am utterly baffled by this.  

Just for giggles, I switched the HDMI to DP (so now both monitors are on DP) and I still have basically the same problem.  One monitor shows in 4k, the other, best I can get is 1200x1600 (which is better than what I had previously, but not the optimal outcome).

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Super User Retired Employee
84 Views

A couple comments:

  1. When you go through the process of putting in a new monitor stand, you can stress a few things (including your back; I know, I put in a dual VESA monitor stand a while back). I would suggest you try replacing the cables you were using.
  2. If backing off the Windows Update helped, I would suggest that there is a possibility that the update has snuck its way back on. It may also mean that a previous version of the Intel drivers is better suited to your configuration than is the latest.
  3. How well can you do if you lower the Refresh rate on the 4K screen to 24Hz. In theory, it should not look much worse than 30Hz did and may free up some bandwidth for the other monitor. There is no way you will get it back to 4K though.

...S

View solution in original post

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Beginner
80 Views

Holy Crap! I think that worked!  I bumped the refresh rate down to 30hz, and all of a sudden, I have the options!

I hadn't paid attention to the previous refresh rate (when it worked) because I was just using the Windows display settings.  But moving that down opened up all of the other resolutions....so I have nothing but thanks to give to you.  

You are the man!  Thanks so much for being diligent with me...I really, really appreciate it!

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Super User Retired Employee
74 Views

Ok, I will accept that, but I had actually argued myself into leaning away from it working -- even though, now that I think of it, my conclusion didn't jive with you having your original working state.

I was pretty sure that a refresh rate above 30Hz was simply not possible with a non-Thunderbolt Hub/Dock that is also consuming USB. Based upon the definitions for USB-C's DP Alt Mode, I was presuming it had to be running 4K@30Hz (I should have asked). In the DP Alt Mode definition, DP can use one, two or all four of the data lanes but, if USB is being used, at least one of the lanes would have been reserved for it and that would (should?) have meant that DP could only use two lanes. Two lanes means maximum is 4K@30Hz.

I am walking away confused. If someone understands this better than I and can explain where I went wrong, please do...

...S

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