WD19DC dock impressions

Finally got a WD19DC dock in the office. We actually got three of them to use with Precision 7530 machines. We are replacing TB18DC docks due to ongoing issues, hoping these will work a little better.

Product page: https://www.dell.com/en-us/work/shop/dell-performance-dock-wd19dc/apd/210-aril/pc-accessories

Photos:

Spoiler

TB18DC vs WD19DC (sorry for dust )







The WD19DC has two cables that aren't as thick as the giant one that the TB18DC has, but they are still pretty hefty.



The WD19DC connector can split apart so that you can use it in a system with only one USB-C port. You get less power and display output options this way. The two ends attach magnetically which is nifty.



Dock with some stuff attached.



Attached to the system... Each connector has its own little white LED to indicate connection.



Got this alert once after starting from a cold boot, definitely with both ends of the connector attached... System seemed fine after booting, though...

This dock does not have any Thunderbolt in it. The displays use DisplayPort-over-USB-C and for everything else, it is basically just a USB hub; the audio and network ports are driven by internal USB-connected devices. (There is no ASMedia USB controller inside so you do not need to deal with those drivers.) It is otherwise roughly equally as capable as the TB18DC dock, except for it does not have a Thunderbolt port on it, so plugging it in will leave your system with no Thunderbolt ports available.

They're still including the giant 240W power adapter, not the slimmer version that comes with the Precision 7730 and 7740.

One nice thing I noticed right away is that there is no delay after reaching the Windows login screen at boot time before the dock-attached devices start working. With the TB16 and TB18DC, it would be several seconds before keyboard/mouse and network started working. With the WD19DC, everything is ready to go immediately. You can also use a dock-attached keyboard and mouse to navigate the BIOS setup and other pre-boot screens, which wasn't possible with the TB18DC (without enabling a BIOS option to auto-approve Thunderbolt devices, compromising security).

With the Precision 7530, graphics switching enabled, and discrete graphics output mode disabled, I tried attaching two 4K displays to the dock. The displays attached to the Intel GPU. They worked, but only at 30 Hz. To get 60 Hz working, I had to turn on the discrete graphics output mode option (in the BIOS setup). This means that the displays are attached to the NVIDIA GPU and not to the Intel GPU. This will not be an option if you do not have a dGPU in your system.

Also, I noticed that the color was off between my two 4K displays. Somehow one of them was set to "RBG" color output and the other was set to "YCbCr422". Setting both to RGB fixed the problem. This was in the NVIDIA control panel.

I've already had multiple occurrences of keyboard stuttering -- a key seeming to be held down even though it is not -- like we had with the TB18DC dock early on. That is disappointing. I'm going to try disabling "C states" in the BIOS and see if that fixes it (that's what worked before).

I've docked and undocked the system several times and it never failed to discover everything (a frequent problem with the TB18DC). One time, I was limited to 30 Hz external displays. I disconnected and reconnected the dock once more and they were back at 60 Hz.

More to come after I've used it for a while.

 

Thanks for the update about this. Keep us posted!

 

Seems like this is the dock to go with for latest gen Precision. I'm losing track of the various docks from Dell and their features... TB18, WD19TB, WD19DC

I wonder if Dell will consider adding about two more TB on next generation Precision so that you can still attach TB devices while using this dock. Otherwise if wanting to use another TB device you'd have to unplug one of the two USB-C dock cables. Its nice they made that an option to separate the two cables.

 

I'd hate to see them go MacBook at this point and replace the remaining "regular" USB ports with USB-C/Thunderbolt ports. Unfortunately there isn't really any room to add extra ports to this system, since the side exhaust ports take up a lot of room and the motherboard does not extend any further to the front past the front end of the keyboard (that space is mostly reserved for the battery). Maybe they could stick them on the back.

 

@Aaron44126 nice quick look at the new dock! It must be nice to always get the latest gadgets at work!

 

Today we tried connecting a 1080p display to the HDMI port on the dock, in addition to two 4K displays on the two DisplayPorts.
On the TB18DC, if I tried this, Windows would see all three displays but only activate two of them. If I tried to activate the third, another one would deactivate. You could only have two active at once.
On the WD19DC, it will run with all three displays in this configuration, but one of the 4K displays is locked to a 30 Hz cap. So, if you want 2x 4K displays at 60 Hz, there is no room to add another display. (You can still attach a third directly to the system via HDMI or mDP and it will work fine.)

 

Ah, that does make it seem like the nVidia dGPU is driving both with HBR3. There is a total of 8 high speed lanes across the two USB-C cables, and it seems they are maxing them out. 6 lanes are used for the 6 HBR3 links needed for 2x 4K60 displays, and another two are needed for USB 3 (bidirectional). That does leave nearly nothing for the last display.

To be specific, it leaves 3.76 * 2 Gbps of overhead, which isn't enough to drive a 1080p60 display without some decent logic (needs 4Gbps, and I don't believe it's capable of aggregating the two 3.76Gbps leftovers).

The Intel IGP would be incapable of driving more than one 4k display and the USB 3 controller, even with dual links. DP 1.2 vs 1.4 (specifically, HBR2 vs HBR3).

The Nvidia GPU should be capable of driving 4 displays simultaneously, implicitly with 16 HBR3 links (assuming the display logic hasn't regressed since Pascal).

 

I noticed that the Realtek USB gigabit Ethernet adapter is attached to a different USB controller internally than the other USB devices in the dock. I am supposing that, in two-cable operation mode, each port uses one lane for USB and three lanes for DisplayPort.

Also, I had audio/video stuttering while trying to watch videos on YouTube both yesterday and today, which never happened with the TB18DC dock. I resolved this today by turning Optimus off, so the NVIDIA GPU is driving all displays. (I think there are some sync issues with apps running on different displays driven by different GPUs which is something that I have run into in the past.) With the TB18DC dock I was able to run all three 4K displays (the internal + two external) off of the Intel GPU.

 

Each lane for USB 3.0 only goes in one direction, so both lanes are needed (up/down, basically). What I'm getting at is, given the technical limitations, there is only 1 USB3.0 bidirectional pair, from the lane allocations.


The Intel IGP is capable of driving three 4k60 displays (specifically, it is capable of driving 3 simultaneous displays), but has some limitations at the output logic w.r.t. bandwidth. However, if wired correctly, it can drive three 4k60 displays. Unlike almost anything else that Intel created, there is no public technical documentation for Thunderbolt (going all the way back to the Sony joint venture with Light Peak). From what I understand, a single TB3 controller can take 2 DP1.2(Alpine Ridge) / DP1.4(Titan Ridge) ports, basically 8 lanes, and aggregate them over the TB3 connection. For two 4k60 displays, that is 31.X Gbps needed. TB3 always prioritizes display data, so of the 40Gbps downlink, it will allocate that 31.X Gbps to display data. TB3 also has a 40Gbps uplink, but that is not relevant to display links (it's also how DisplayPort 2.0 can use TB3 PHY/Protocols to get 80Gbps with the same 4 lanes - it changes the two 20Gbps uplinks into two 20Gbps downlinks).


Going back to the USB controller thing, USB 2.0 and USB 3.0 are different protocols and use different wiring, even within USB-A and USB-C ports. The Realtek GbE is connected to the USB 3.0 (XHCI) on the TB3 chip (which serves as USB 3 Type-C host, when not operating in TB3 mode), but USB 2.0 is passed through the TB3 chip from the southbridge. So unless if you plug in a physical USB 3.0 device, the data will be transported using the separate USB 2.0 host (and different USB hub), since it is using different wires altogether. This is true of USB-A and USB-C.

(USB 3.0 flash drive connected to dock; SanDisk Ultra T C USB Device)



(USB 2.0 flash drive connected to dock, replacing the USB 3.0 flash drive; Corsair Voyager)


Further expanding (but very tangential), USB-C has 20 pins, basically. 8 are used for high speed data pairs (differential pairs). These 8 pairs allow for 4 high speed lanes. There is also a physical USB 2.0 link that takes another two wires (D+ and D-). Technically 4 wires, since it uses a simple "reversible connector" layout, but only two are used at a time. Ground, sensing, and power take up the rest. Remember VirtualLink? That connection is a standard DisplayPort Alt-Mode over USB-C setup, except it electrically upgrades the 4 (2 active, 2 inactive) USB 2.0 wires to a USB 3.0 connection (2 differential pairs, 4 wires), and needed upgraded wires as a result. Also VL added USB-C PD into the mix, which isn't always standard on USB-C ports.



I'm in a rush before lunch, so if anything is unclear, please let me know and I will try to reorganize it tonight. Otherwise, I'll assume my post smells nice and shines.

 

Oh, that makes sense. The gigabit Ethernet adapter is probably the only USB 3.0 device in the mix for me, which is why it showed up at a different location in the tree.