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Mark141
1 Copper

TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)

I'm using a TB16 with a XP13 (9350) and a single 4K monitor (Dell P2715Q). The setup works perfectly at 30Hz but at 60Hz it flickers continually. By flicker I mean the external display switches to black for 2 to 3 seconds several times per minute. The BIOS of the XPS13 and all drivers are current. MST is turned off on the monitor. The setup works fine at 30Hz. I tried enabling airplane mode as others suggested in this forum and it made no difference. I have also tried several DisplayPort (mini and full) cables with no success. 

This is not an issue with the monitor as I can hookup a Surface Pro 4 at 60Hz without any issues. 

One interesting thing is when I hookup the SurfacePro4 it defaults to 60Hz but when I hookup the XPS via the TB16 the default refresh rate is 30Hz and I need to change it to 60Hz using the display adapter settings.

Is anyone successfully using a similar setup without flicker? The TB16 specs list it as capable of supporting 2 4K monitors at 60Hz.

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7 Replies
Not applicable

RE: TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)

I have the same laptop, dock, and external screen. I experienced the same bug when running at 4k/UHD resolution: 30hz went OK, 60hz went bad.

The silly thing that worked for me though, was not to use the mini-DP port on the back of the TB16, but rather the standard-sized DP port on the back of the TB16.

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Mark141
1 Copper

RE: TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)

Thank you! I only had a mini-DP to DP cable so I tried reversing it and that didn't work. I tried a mini-DP to mini-DP cable as well and had the same problem. I bought a standard-size DP to DP cable and haven't had a single problem with flickering all day. I don't know if the problem lies in the dock or the monitor but  using a full size Display Port cable is the only way to currently use this setup at 60hz.

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plivy
1 Nickel

RE: TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)

I have the same laptop and same dock, but I have an LG 27UD68-W (27" 4k monitor). I use both the external monitor and the laptop screen at the same time (extended display). The monitor has two HDMI inputs and a full size display port input. When I connect the monitor using only a display port cable, it connects at 60hz and full resolution, but it goes black for a few seconds every so often. Sometimes it loses the signal completely and stays dark, and then maybe a while later it will just turn itself back on out of nowhere. If I connect the monitor using an HDMI cable, it doesn't cut out, but the refresh rate is limited to 30 hz, which makes my eyes bleed. Hilariously, if I connect the monitor using both an HDMI cable and a Display Port cable and tell the monitor to display the signal coming through the Display Port cable, I get something in the middle where the refresh rate appears to be above 30 hz, but it isn't quite 60 hz, and it stops cutting out. When I do this Windows thinks there are two external monitors, so I tell it to mirror the displays, which seems to work. When using this setup the Intel HD Graphics control panel tells me the displays are in "Hybrid" mode, or something like that.

It would be really nice if there was some way to get this monitor to just use the Display Port cable and a refresh rate of 60hz! The documentation for the TB16 and my laptop make it seem like this should be possible, but I just can't get it to work. Tech support has done everything from replace my logic board and wifi card to have me completely wipe the computer and re-install. I wish someone at Dell who knows what the heck is going on would explain this to me.

sbtecture
1 Copper

RE: TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)

It's happening to me, too. I have two 4K monitors so using two standard size DP cables isn't an option. The extra HDMI cable trick seems to be helping so far, but it's pretty frustrating that Dell hasn't acknowledged this issue.

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sbtecture
1 Copper

RE: TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)

Same problem, but I have 2 4K monitors, so using different cables is an option. The extra HDMI cable trick seems to be helping so far, but it's pretty frustrating that Dell hasn't acknowledged the issue.

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Cerberus-
1 Nickel

RE: TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)

Hi,

this is not really a TB16 issue. I use the TB16 with following devices:

Dell XPS 9350 (Developer Edition > Intel Wireless)

Lenovo P50

Lenovo P51

It works fine with Lenovo using 1x4K + 1x2K Display. With the Dell device i get constant dropouts/flickering.

I get the same issue using USB-C > DP or USB-C > HDMI Adapters on the Dell. Looks like the USB-C Port have trouble keeping up. There is some known issue involving WLAN RX Power and the USB-C Port.

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JDNinQLD
1 Copper

RE: TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)

Same thing for me.  I run two 4k ASUS MG28UQ with the TB16 and a Dell XPS15 9550.

The ASUS monitors flicker off and on randomly and occasionaly drop out completely.  When one drops out I haven't found a reliable way to bring it back online - turn off then on, reboot the laptop, reboot the TB16 etc all typically fail (but randomly occasionally succeed).

Sometimes one of the monitors will come back on, but not really - Windows will make its little noises as the device is "plugged in" - the screen will stay black - but it'll be visible in the Intel or Win10 display settings, but with no attributes - i.e. the resolution, orientation etc will show as empty fields and the picture of the monitor that shows in either of those two places will be a tiny square - a fraction of the size of the other two monitors.

Oh, and all of the USB ports in the TB16 are flaky.  Sometimes they work and sometimes they don't.  They'll all be offline and then randomly a couple of them might start working or perhaps all of them.

Even when they're working they're worthless for using a mouse - I have to run the mouse from one of the two ports on the laptop itself.  Running the mouse from one of the TB16 ports results in a wide spectrum of performance - occasionally working "normally", then degenerating into partially working (the mouse skips all over the screen - working / not working / working / not working / working ...), and then periodically it just flat out stops working - even if the paired port for example (with the keyboard in it) still seems to be working fine.

Yes, all the bios, thunderbolt, etc drivers are current.

I could've just bought a thunderbolt-to-2xDP adapter, plus a 10-way USB 3 hub and (presumably) I'd have a functioning system without the cost and b.s. of dealing with these Dell TB16 docks.  I run an identical setup at home and at the office - same laptop but duplicated monitors + duplicated TB16 at each place.  Same behaviour in both environments.  It's a MS mouse + keyboard at the office and Logitech mouse + keyboard at home and same behavior from each of the mice, so is not a mouse problem.

-JD