Dell WD19TB Thunderbolt 3 dock with three and four displays

This article discusses using the thunderbolt dock with three 1920×1200 screens and four screens.

I had the opportunity to experiment with a WD19TB Thunderbolt dock while evaluating the new XPS 13 ultrabook. One of the questions that I sought to answer was whether the dock was capable of outputting on 3x 1920×1200 monitors at 60fps. The other was whether it was possible to use the three eternal screens plus the internal screen of the XPS 13 as a 4th display.

The official documentation (PDF) for the WD19TB is poorly laid out, unclear and accordingly is open to interpretation. This article discusses my findings.

Three external 1920×1200 monitors

Using three identical Dell U2415 screens running at 1920×1200, it was possible to connect all three displays at 60Hz. Using 2x DisplayPort and 1x HDMI yielded the correct resolution. Equally, using DisplayPort 1.2 in a daisy chain off of one of the DisplayPort connectors worked as well.

All three screens loaded at 1920×1200 @ 60Hz and there were no signs of lag or stuttering in 2D operations. I did notice secondary issues when playing 720p video from YouTube on just one of the screens. Under what in 2020 would be considered to be trivial load, the Intel Graphics chip on the 2020 built XPS 13 9370 was being taxed – you to 40% GPU utilisation.

This made the XPS 13 run hot, and eventually the fan in the dock would kick in. Creating a level of noise that some may find undesirable or even distracting. Although the i7 model, the sample 4K unit did not have the higher spec Intel Iris graphics chip. It was also running on slower, hotter DDR3 memory. Consequently, Video playback while supporting 6,912,000 display pixels was clearly taxing the sample XPS 13.

Three external monitors + the internal XPS 13 display

In my workflow, I keep 4 displays in use. My main activities are present on the external screens, while I will keep tertiary activities such as email on the lower, built-in screen.

So was it possible to use the WD19TB with four screens?

I do not usually run the built-in panel at its native 3200×1800 as the mismatched Windows font scaling doesn’t play nicely with non-UHD external screens. Despite this, it was not possible to use the three WD19TB external screens plus the internal display.

It was possible to have any combination of 3 screens enabled, but attempting to enable the 4th would iteratively disable the first screen in the display list. I repeated the test after lowering the 1920×1200 resolution of the three external monitors to 1920×1080. Even with all 4 screens running a sub-native resolutions, the Intel graphics driver refused to allow 4 screens to be used.

This is likely a limitation of the Intel Graphics chip and is nothing to do with the . Plugging in my USB DisplayLink adapter allowed a 4th screen to appear as normal. Had I been able to test with an external GPU enclosure, it likely would have been possible to use all 4 screens via Thunderbolt.

Although the use of a USB display source such as the or is undesirable. In most 2D workflows, it offers an acceptable route to 4 screens. Their CPU acceleration is however a limiting factor for 3D or high frame-rate use.