4K monitor not working thru new dock

[djasontaylor]

Has anyone else tried to connect a 4k monitor via the new dock? Mine is not working unless I connect directly to the surface display port. FYI - you cannot connect a cable to the mini display port while the dock is connected. The dock plug covers 1/2 of the display port.

 

[jnjroach]

I'm running an Older Dell 4K (P2815Q) through the new dock on a SP4 and a colleague is running the same on his Surface Book....

 

[djasontaylor]

I'm running an Older Dell 4K (P2815Q) through the new dock on a SP4 and a colleague is running the same on his Surface Book....

What type of cable? I was able to get mine to work with a HDMI plus a mini adapter. But a HDMI to mini cable worked plugged into my book but not when plugged into port on the dock

 

[protip]

I've got two DisplayPort 1.2 (60 Hz) 4K displays on my desk. The reputed support for two 4K monitors was an important factor in my decision to purchase the Surface Book and the dock. However, so far, I have only been able to successfully get the dock to drive one of the two monitors at a time.

The cables are standard mini-DP to full-DP, both DP 1.2 compliant.

I'm hoping this is a software issue because if the dock doesn't actually support two 4K monitors, this won't really work as a workstation replacement.

 

[jnjroach]

What type of cable? I was able to get mine to work with a HDMI plus a mini adapter. But a HDMI to mini cable worked plugged into my book but not when plugged into port on the dock

Mini DP to DP....HDMI only supports one Monitor without an active MST Hub

 

[Houston R32]

What you might try is setting up the 4ks at 30 Hz. I have 2 4k monitors and a 1080p monitor off my SPro3. I use an MST hub for the 2 4ks connected directly to the Surface and the 1080p to the SPro3 dock. To get it running with the 2 4ks, first one came up at 4k 60 Hz, I set it to 30 Hz and then the other 4k came up at some resolution and I set it to 4k and 30 Hz and things worked. It may take a few tries. I just got my SPro4 Dock to see if it will allow me to get rid of the MST hub, but have not had time to play with it.

I am pretty sure the video on the SPro3 is limited to what I am doing based on the processor chip limits. The SPro4 has more video, so it might do them at 60 Hz, but maybe the drivers or something else is limited. I do not know exactly how many DP links are coming through the connector to the dock and that may be the limit in the end.

 

[protip]

30 Hz is unacceptable to me. I have been using a 30 Hz 4k for nearly two years and part of the incentive to upgrade to a Surface Book was the two DisplayPorts each supporting 4K displays. It does support one at 60 Hz, but it won't turn the second one on. I know the hardware supports DisplayPort 1.2. The question is: is this a driver/software problem (I hope so) or is the hardware incapable of two 60 Hz 4K displays?

If this turns out to be a hardware limitation, I am going to be upset. But ultimately, it would just mean that Surface Book isn't the device for me and I need a proper workstation. It would also mean I need to remind myself that "desktop replacement" is an oft-used but usually fallacious claim for portable devices. It really means "This portable device is about as good as your three-year old desktop you want to replace" and not "This is as good as a desktop available today."

 

[zhenya]

I hope to hear that these new devices are working with 2 4k at 60hz soon. The SP3 can do 2 at 50hz and these Skylake chips are supposed to do 60hz. Having them be able to do so would be a big part of the impetus for me to upgrade.

 

[Houston R32]

Displayport 1.2 link is limited to a single 4k monitor at 60 Hz. Driving Multiple Displays from a Single DisplayPort Output - DisplayPort
That is why the important point is how many links are coming out of the connector. If it is only a single DP 1.2 link, then it cannot drive two 4k at 60 Hz, period. If it is two DP 1.2 links then it should be able to drive both 4k at 60 Hz. But a Skylake only has three available video outputs. Assume one to the internal panel, one to the side port and one to the dock/power port and you have the three available video outputs. So that means while the dock may have two miniDP ports, their configuration is unclear but most likely there is an internal MST hub, which means a single DP 1.2 and thus only one 4k at 60 Hz.

You should try to run one 4k from the dock and one directly from the Book miniDP port. That is your best bet for getting to two 4k at 60 Hz, if they are indeed two different links from the Skylake. That is a much better chance than trying them from the dock alone.

On my SPro3, I had to connect the MST and the two 4k 30 Hz to the side miniDP port. The SPro3 dock port was too flaky.

 

[protip]

Awesome feedback. I'll have to give that a try soon. I'll need to get a really slimline mini-DP to full-DP cable because the mini-DP port on the Surface Book base is situated too close to the dock connector to fit my two current mini-DP connectors.

I would also be okay with losing the built-in display when powering the two 4K displays, as long as they are at 60 Hz. I wonder if there is a way to instruct the SB to shutdown the main display when docked so as to allow the chipset to focus on the external displays.

 

[Houston R32]

To get the internal display to shut off you need to make one of the other displays the main display and then you can shut it down. But you shouldn't have to do that as it should drive the three displays fine.

 

[ccates22]

Has anyone else tried to connect a 4k monitor via the new dock? Mine is not working unless I connect directly to the surface display port. FYI - you cannot connect a cable to the mini display port while the dock is connected. The dock plug covers 1/2 of the display port.

yes, I noticed that too! How annoying.