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HowChris
1 Copper

U2415, Dual, Daisy chain DP1.2 issues

Connected dual monitors via DP1.2 using UltraAV mDP to DP cable with screens in extended mode. Result , both monitors flash black screens intermittently and randomly-  either or both then eventually show only a black screen. Any solution available? Both monitors seem to have no problem operating in DP1.1 individually, so issue only arises when DP1.2 enabled and daisy chained. Had initially tried the DP cable which came with the monitors but changed to UltraAV to see if this would cure the problem ( it didn't). Monitors made in August 2014 Rev A00 serial numbers CN-74261-480-3TCL and 48S-130. PC Alien R3 desktop as built but replacement Dell m/b DP/N 046MHW. Graphics card R6870 2x mdp, 2x VGI and 1x HDMI ports.Windows 8.1. Monitors using recommended resolution and self test showed no problem. Monitors purchased via Amazon. Tried factory reset which disables DP1.2 but have to reinstate DP1.2 to daisy chain but same result.

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18 Replies
Moderator
Moderator

RE: U2415 Ultrasharp Monitors and daisychain

Be sure to update the AMD Radeon HD6870 to the latest driver.

A00 August 24, 2014
A00 August 28, 2014

So this is the setup you are using?

AMD Radeon 6870 mDP out --> UltraAV mDP to DP cable --> #1 U2415 (#4) DP in (DisplayPort 1.2 Enabled)

#1 U2415 (#6) DP out --> UltraAV DP to mDP cable --> #2 U2415 (#5) mDP in (DisplayPort 1.2 Enabled)

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HowChris
1 Copper

RE: U2415 Ultrasharp Monitors and daisychain

yes, all correct except that I use the supplied Dell mDP to DP cable between the monitors. I have to switch the monitors on and off several times before the black screens stop. Note that the OS continues to run in the background despite the black screen. 

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Moderator
Moderator

RE: U2415 Ultrasharp Monitors and daisychain

Take the UltraAV mDP to DP cable out of the troubleshooting and only use the Dell provided cables. Any change in the issue?

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HowChris
1 Copper

RE: U2415 Ultrasharp Monitors and daisychain

No, there was no change. To me the issue seems to be the "handshake" between the master monitor and the pc because the monitor screen is black even though the os has gone through post and loaded. If I then switch off the monitor and then back on the os is running on screen. If I start then start to enter the password and the screen again blinks black the password carries on and is activated and the os runs normally. After switching off/on  the monitor a couple of times the screen stops blinking so obviously the pc and the monitor have recognised each other. The question is how to correct this.

I have run Alien autopsy and all the other checks that you have mentioned in previous responses to other queries but nothing has changed.    

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Warren-G
1 Nickel

RE: U2415 Ultrasharp Monitors and daisychain

Not sure if this will help at all?

www.dell.com/.../EN

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customerAW
1 Copper

RE: U2415 Ultrasharp Monitors and daisychain

I am currently experiencing the same problem as HowChris though with a slightly different configuration.  Using only the dell-provided cables, my configuration is Laptop_DP->Monitor1_mDP, Monitor1_DP->Monitor2_mDP.

The screen flicker does not appear to affect peripheral connectivity as open windows do not re-position to the laptop screen as if the monitors were disconnected.

Monitor2 currently has DP1.2 disabled as it was suggested that the last monitor in the chain should have it disabled to explicitly identify it as the end of the chain.

Disconnecting the monitors and reconnecting them ends the flickering when it does happen, but this is a huge hit to productivity as not only do I have to stop my work to address the sudden flickering, but on top of that, all open windows get rearranged in the process.  This is far from the ideal solution and frankly should never become an option.

I have been experiencing this problem intermittently for months now and at this point I am fed up with it.  I regret not immediately returning them when it first came up.

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Moderator
Moderator

RE: U2415 Ultrasharp Monitors and daisychain

customerAW,

What OS, video card, driver version, U2415 revision number and serial number?

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remudapro
1 Copper

RE: U2415, Dual, Daisy chain DP1.2 issues

I'm experiencing this same frustration. Has a fix been identified? My AMD hd6870 drivers are on the most current version. I have to believe this is a Dell Daisy chain issue as there are many other users with similar symptoms that are using a different graphics.

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asbel
1 Copper

RE: U2415, Dual, Daisy chain DP1.2 issues

I am having the same problem with my 2 U2415 A00 monitors daisy chained. In fact, it just started happening the moment I started this reply. :/ I am a software engineer and after diagnosing this on my end I am fairly confident this issue has nothing to do with the computers, cables or anything else external to the monitors. I have found that when this occurs, putting the monitors into power save mode can remedy the problem temporarily. However, it eventually returns. These monitors are not reliable. Does Dell acknowledge there is a problem with MST on certain revs of this monitor?

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