Screens blink on/off when I daisy chain my 3 new U2415! - Monitors Forum - Peripherals - Dell Community

Screens blink on/off when I daisy chain my 3 new U2415!


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Screens blink on/off when I daisy chain my 3 new U2415!

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Just bought 3 new U2415's for their daisy chaining capability.  When I connect them as per directions, they do indeed daisy chain, but almost immediately they begin blinking to black screen and on again, like lights on a Christmas tree (only slower). 

My setup:
Mobo:  Asus P8P67
GPU:  Radeon HD 6850
SSD:  Samsung 850

At first, all I could get the monitors to do was mirror each other. 3 expensive monitors showing the same thing doesn't work for me.  After 3 hours with Dell phone support they finally told me no mas without solving the issue, because the monitors were not connected to a Dell PC.  Disappointing.

So, I disconnected all my drives except the SSD and did a fresh Windows 7 install from DVD, and then downloaded and installed all of the Windows updates. Installed Dell monitor driver off of DVD that came with monitors. Updated Bios and latest chipset, GPU drivers and AMD Catalyst Control.  Nothing else is on the SSD besides Win 7, Windows Security Essentials, Malwarebytes. No other storage drives.

I reset all of the monitors to factory settings and then Enabled DP1.2 on the monitors #1 & #2.  Monitor #3 was already Disabled.  Voila...Windows recognized 3 independent monitors and I was very happy. Until they started to blink on and off after a few minutes.  The AMD Radeon HD 6850 specs claim to support:

  • DisplayPort 1.2
  • Max resolution: 2560x1600 per display
  • Multi-Stream Transport
  • 21.6 Gbps bandwidth
  • High bit-rate audio

My monitor cables are DP1.2 and brand new. Windows is fresh, bios and drivers are up to date. This is driving me crazy.

So, anyone have some ideas on what I am doing wrong? Is there a super secret Dell pay support line that I can call? I am willing to pay, provided I get this solved.


All Replies
  • I would start by turning everything off. Disconnect monitors 2 and 3 from the setup.

    * Test monitor 1 by itself. Does it have the blinking issue? (Y/N)
    * Turn the computer and monitor 1 off

    * Add monitor 2 in a daisy chain:
    Does monitor 1 have the blinking issue? (Y/N)
    Does monitor 2 have the blinking issue? (Y/N)
    * Turn the computer and monitor 1/2 off

    * Add monitor 3 to the daisy chain:
    Does monitor 1 have the blinking issue? (Y/N)
    Does monitor 2 have the blinking issue? (Y/N)
    Does monitor 3 have the blinking issue? (Y/N)

  • Hi Chris...thanks for your reply.

    #1 by itself direct connect via DP1.2 cable to blinking

    #1 daisy to #2....both begin to blink after a minute or two

    #1 daisy to #2 daisy to #3.....all three begin to blink after a minute or two.

    Any thoughts?  Is my GPU capable?

  • Can you test monitors 2 and 3 as  #1 in the chain? Is there another desktop computer to test them on?

  • Chris...I have tested every combination..with same result.

    Thinking this might be caused by an older GPU, yesterday I decided to upgrade the majority of my system and purchased and installed:

    CPU:  Intel Core i7 4790K

    MoBo:  Asus Z97-A

    OS:  Win 7 Pro

    My 3 U2415s are all REV A02

    I did retain Corsair HX650w PSU, which has more than enough power to drive my rig and Cooler Blaster 212+ to keep the i7 chill.

    So...I essentially have a brand new and up to date system.

    What is going on here?

    The good news is that the random black screen blinking has decreased from once every 90 seconds/per screen to about once every hour or so.  

  • I hit "Post" to fast.

    I meant to say that even after doing all of these upgrades to create a very current system, the screens all still randomly go to black and then back on, when in daisy chain.   No issues if running only a single monitor.

    The good news is that the rate at which they black screen blink has decreased.   I did notice that when I was in the midst of copying 12 gig of files from one of my HDDs to my SSD the pace of blinking increased significantly, similar to what I saw before upgrading components.  How could this be impacting MST?

    What is going on here?

  • I also forgot to mention that I purchased a new GPU as well:   Sapphire Radeon R7 380

  • Did you install the latest AMD driver for the Sapphire Radeon R7 380? If yes, the only other thing to try is to get three monitor exchanges there. Then, test all three replacements. You will have six there to mix and test. But by the end of testing, three will have to be sent back to Dell.

  • Hi Chris....I wanted to give you and the community an update.

    I upgraded my GPU, again:

    From:  Sapphire Radeon Nitro R7 360 2GB (new a week ago)

    To:      Sapphire Radeon Nitro R9 380 4GB (yesterday)

    Since I did the swap yesterday morning, I have only seen one monitor flash to black screen, once.  The new card is faster and has twice the memory capacity.  I don't know which of those features caused the change in behavior, but I am just glad the monitors aren't blinking, for now.  Based solely on my experience, it would appear that in order to daisy chain the U2514s, you need a reasonable recent  and powerful GPU card.  If this is the case, where does Dell disclose this is minimum system requirements?  Is there a Knowledge Base discussion on this issue?

    QUESTION:  Can the included Dell DP to Mini DP cables be used to daisy chain?  After I saw some stability in the monitors I tried to use these cables to daisy chain #1 to #2 and #2 to #3, as I wanted to return the $27, 3ft Full DP to Full DP cables I bought at Micro Center.  Once I booted up, only #1 lit up and went to Window.  #2 and #3 flashed "No DP Cable".  I swapped both mini to full DP cables to see if one was bad, same result.  Why won't these work?

    Thanks for your help.

  • If this is the case, where does Dell disclose this is minimum system requirements?
    * We only listed this in the Manual =
    U2415 supports the DP MST feature. To make use of this feature, your PC Graphics Card must be certified to DP1.2 with MST option. The default out of factory setting in the U2415 is DP1.1a. To enable MST connection, please use only DP cable as provided in box (or other DP1.2 certified cable) and change the DP setting to DP1.2.

    Is there a Knowledge Base discussion on this issue?
    * No. I cannot find one.

    Can the included Dell DP to Mini DP cables be used to daisy chain?
    * They should:
    Sapphire Radeon Nitro R9 380 4GB DP out --> U2415 DP to mDP cable --> #1 U2415 mDP in (DP1.2 MST Enabled)
    #1 U2415 DP out --> U2415 DP to mDP cable --> #2 U2415 mDP in (DP1.2 MST Enabled)
    #2 U2415 DP out --> U2415 DP to mDP cable --> #3 U2415 mDP in (DP1.1a Enabled = DP1.2 MST Disabled)

  • I just wanted to add my 2 cents, since the blinking on my two Daisy Chained Dell U2415 was driving me completely MAD but now it is resolved.

    Anyway, I am running:

    Windows 10 x64

    AMD Radeon R5 340X

    HP Z220 Workstation

    Two Dell U2415 monitors that are version A02.

    I am NOT using Dell drivers and using the AMD drivers that come down from Windows Update only.

    Basically, the monitors would blink randomly every once in a while with no "rhyme or reason" so sometimes one, sometimes both, sometimes every 5 minutes, sometimes every hour; but it was driving me crazy. I finally decided to unplug everything and decided to switch the cables as everyone has mentioned.


    AMD DP --> Dell #1 mDP

    Dell #1 DP --> Dell #2 mDP

    I tried setting one to DP 1.2. Both to DP 1.2. Tried Dell drivers. Tried AMD drivers. Updating Drivers. Changing various settings, but always blinking.


    AMD DP --> Dell #1 DP

    Dell #1 DP --> Dell #2 mDP

    I went ahead and did FACTORY RESET on both monitors and then enabled DP 1.2 on Dell#1. No more blinking and it has been in use for more than 8 hours, so it looks like that solved my problem.

    I was using two identical cables from "Cable Matters" that goes DP to mDP, but the blinking stopped when I changed the initial cable coming out the video card. So my suspicion is that the DP to mDP cable somehow cannot handle all the initial throughput and I will eventually go 3 monitors, but now I know to try the DP/mDP cable switch.

    Thanks and just sharing, since I was checking the boards for solutions...

  • I just bought a second screen Dell U2515H (one year after the first) and I had the same black screen problem. I have a Surface Pro 3 with a docking station.

    At first, I had activated the DP 1.2 on both screens and the problem was very frequent. Then, I disabled the DP 1.2 on the second screen (Intel graphics card) and the problem was less frequent. But too common, only a few minutes before the black screen.

    I then reversed the screens by directly connecting the new screen to the docking station (initially the old one) and the problem does not happen at the moment.

    In Device Manager, I noticed that there was a difference between the two screens:

    Old screen: DELD06E

    New screen: DELD06F

    Maybe Dell corrected the problem on the new screens. Can you confirm ?

    I just modified the configuration, I have to check for a while before confirming that it works.

  • Thanks for this answer - I have two Dell U2717D and had DP -> mDP and DP -> mDP and had both flashing constantly. Been using it like that for over a year. Just switched the first monitor to DP -> DP and it no longer flashes! The second monitor is still mDP -> DP and unfortunately still flashes, but less often. I am on a Dell Precision 7510 so latest hardware Windows 10 x64. I have used the same setup on a Precision M4700, Precision M4800 (Windows 7 x64) with the same blinking. My coworkers (at least 4 of them) have had the same setup and the same blinking on daisy chain. Not sure if it is the cable, or these models of monitors, but they definitely have an issue. Solution is not to use mDP it seems. Not sure how it slipped past testing!