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hfi
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Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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I have two U2715H monitors connected via one mDP->DP cable each to an E-Port Plus docking station (actually a EURO2 Advanced Port Replicator) in which is seated a Latitude E7450 laptop. All items are brand new. The E7450 is equipped with 16 GB RAM and two graphics cards: Intel HD Graphics 5500 and NVIDIA GeForce 840M; selection is automatic, which usually means the 5500 is in operation. It runs Windows 7 Enterprise SP1 (64 bit). The docking station apparently has DP 1.2a capabilities (for daisy chaining) but DP 1.2 is disabled in both monitors.

I have successfully set up the system to have the Windows desktop span both monitors at 2560x1440 resolution, even with the Latitude's internal screen as a third extension at its full resolution (1920x1080). The Main display may be set to either of the two (or three) and I can successfully move the sequence of the monitors around (left, middle, right).

So there is no doubt about the system's capability to support the intended configuration. However, when I dock the Latitude (mostly with the lid shut) and boot it, most of the time it cannot reestablish the configuration of the two external monitors. Some of the symptoms are: One or both monitors go black, indicating cable connected but no signal arriving from the docking station. If there is a picture on one of the monitors at startup, it may or may not contain the login screen. (I can still log in because I know what keystrokes to send.) If the login screen is visible, it is usually in a low resolution. If I have several screens active, but one is black, I can move the mouse pointer (or an entire window) across the black screen (in the middle or on the side) but it is not visible there.

Both monitors come straight from the box and the only change I have done is to switch from DP to mDP as input channel. I have reseated the cables and swapped the cables between the two DPs on the docking station. I have turned the monitors off and on. I have run the self test as prescribed on both monitors. The laptop connection on the docking station is a bit wobbly but I am using the supplied spacer for the E7450 and making sure the connection is correct and stable. I have updated all drivers and the E7450 BIOS. I have recently seen a reference to a BIOS for the docking station; I didn't know it existed, but I cannot find it.

The instructions packed with the monitors had a note about consulting the supplied CD for using the monitor at maximum resolution. The E7450 doesn't have an optical drive but I have read all the documentation for the monitor at Product Support without finding anything to illuminate the situation (beyond making sure that the graphics card and the drivers are up to the task).

Once I have logged in, I can manage to get everything back in order by randomly(?) reducing screen resolution, changing the position of the main display (left-middle-right), deselecting and reselecting mDP as input channel, and forcing other changes. Once both or all three screens are in operation, I can set them all to maximum resolution and start working. However, this is rather bothersome and I would like to have a stable setup.

The configuration seems to survive power cycling of the laptop/docking station but not if I also undock the laptop. I should mention that when I undock the E7450, I may be using it in other configurations with or without other external monitors through other ports, before I turn it off and later re-dock it as described. However, for the first month I had two older non-Dell monitors of lesser resolution (on DVI and VGA ports) connected to the docking station and the configuration was stable, and for years I have been used to my older Latitude with an older docking station remembering its peripherals between different hardware setups.

Please, anyone - and Dell support staff in particular?

(Edited/updated after move from Forum/Peripherals/Monitors to Forum/Laptop/Video)

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hfi
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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No responses, so I will add my own, on the way towards a solution, which I believe requires driver enhancements. Are you listening, Dell?

Together with a colleague who knows better than me what to look for, we discovered:
- The Intel HD graphics control panel -> Display port topology only discovers one, not two display ports. This could be a problem with the panel or with the graphics driver.
- Both Intel and Nvidia have more recent driver releases for their respective hardware components in the Latitude E7450 than those available from Dell but they cannot be installed directly. (NVidia 353.06 vs 341.27; Intel 10.18.10.4222 vs 10.18.14.4099 - I suspect digits 5 and 6 reflect an OEM numbering scheme). Intel says their driver update includes critical fixes for display support.
- When we attempted to install the latest Nvidia driver, the display flashed in what seemed to be a non-trivial manner (before the update was automatically aborted). This could be related to a conflict between the two drivers.

I also discovered that even when only one of the Dell U2715H monitors is connected, it frequently goes black when it shouldn't. So it is not a question of a dual monitor configuration as I originally thought. I have also swapped docking stations to eliminate random hardware error in this component. The Intel driver's handling of display port(s) seems to be the most likely culprit.

Guessing from seeing repeated patterns of monitor behavior, a more precise diagnosis could be that the monitors do not always go out of power save mode when they ought to. I suppose that for a workaround I could experiment with power settings to make sure they never went into power save mode (so they wouldn't have to be brought out of it again) but I haven't done so.

We have, however, found a workaround that gives a much more stable configuration: to daisy-chain the two monitors from one display port. Even in this configuration the second monitor has gone black on occasion but for now this is an acceptable workaround. However, the Windows Main Display needs to be the first in the chain, or else it will not work properly.

Turnhout
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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Thanks for the tip!

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Turnhout
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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Received some feedback from a customer with this issue, a newer intel video driver improved but didn't fix the issue

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ksele
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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I have the same problem! But with two U2515H displays, Lattitude E7450, Euro 2 docking. Using displayport.

Are you looking in to this Dell?? 

Hoped that windows 10 would help me, but it dont look like it will help. I will try to chain the monitors as you did.

I had no problems with Win 7 and resolution at 1920x1080. But i want the higher as this was the reason why we did buy these monitors! All products is Dell. So come on Dell. Please check out dis issue!

Best Regards

 

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hfi
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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Update: I have now installed new drivers: Intel 10.18.14.4170 (dated 16 March, 2015) and Nvidia 10.18.13.5362 (dated 22 July, 2015). I found them both by browsing Dell's support section for the 7450. Neither Windows nor Dell software was able to discover these automatically, and the wrappers have a more recent date (they contain other drivers as well). I cannot explain why these version numbers do not match those I referred to previously. My configuration as described (with the daisy-chain setup) has now become much more stable. Over the last week and with these more recent drivers I have hardly experienced any screen blackouts, except occasionally when booting or rebooting the computer. A new reboot usually solves that problem. So the situation has improved with the new drivers but it is far from as stable as it should.

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Turnhout
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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Had 1 laptop with this issue; Dell replaced the mainboard last week

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hfi
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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What did you do to make them replace the motherboard (e.g. any particular diagnostics)? And - more significantly - did it help?

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tcingle
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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Here at Penn State University, I have had many colleagues voice the same issue with erratic monitor behavior.  Things seem to be more stable with the latest BIOS update (A05) and Intel video drivers.  

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Turnhout
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RE: Latitude E7450, E-port 2, U2715H - dual monitors - unstable configuration

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Haven't been able to test this firmware, sounds like a possible fix?

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http://www.dell.com/support/home/us/en/04/Drivers/DriversDetails?driverId=29D8V&fileId=3482013792&os...

Synaptics VMM3320 MST HUB Firmware Update

This package provides Synaptics VMM3320 MST HUB Firmware Update and is supported on Latitude E7250/E7450 that are running the following Windows Operating System: Windows 7, Windows 8 and Windows 8.1

Fixes & Enhancements

Fixes
- resolves momentary screen flash when using external DVI/VGA display