Drivers & Software

[garf]

I've had a horrendous struggle with Dell regarding my high spec laptop (Precision 7730 with WX7100 GPU) driving a WD19DC docking station through dual connected USB-C connections via two Display Ports to a BenQ PD3200U on each.  It used to work fine, with both monitors running at 4k native resolution and 60Hz with 8bpc.

This fits within the bandwidth available via the dual USB-C connectors, detail in the Dell manual for the WD19DC, and this configuration at this resolution is supported by both the Precision 7730 with WX7100 and the WD19DC docking station.

So ... given that the same cables and monitors can independently run a single monitor at 4k 60Hz 8bpc, it appears to be a driver issue.  Sometimes Windows 10 sees the second monitor but can't establish resolution or attributes, so it can't use it.  Reboot usually "fixes".  Hate that "fix".  Not really a "fix".  Meh.

Dell blessed driver version: 19.30.28.03

Windows 10 Pro 2004 (19041.572)

Can anyone suggest ...

a) How to debug this, when I change the bpc using AMD Radeon Pro Settings app?

b) How to debug this when I connect/disconnect a display port monitor on the WD19DC to see what the AMD driver is doing/assessing?

Right now, I am running one monitor at 30Hz so I can keep the colour space at 8bpc on both monitors.  Not great, given BenQ and Dell both agree there is nothing wrong or unsupported in my setup.

Thanks in advance!

[pokester]

fsadough‌ may be able to offer some advice on this. I seem to recall a discussion similar to this in the past. 

[fsadough]

The problem could be related to your docking station. Try to connect the BENQ monitors directly to your laptop via HDMI and mDP and see if you get 4K@60Hz or not. In any case you need to contact DELL for tech support.

[garf]

I spent 4 months speaking to Dell about this earlier this year.  Returned two docking stations (a TB18 and a WD19DC), spoke with BenQ, and so now I'm with AMD.

With three vendors involved it is always going to get difficult when a problem turns up that is hard.  I do get 4k@60 on both monitors when connected via mDP and HDMI to the laptop directly.  My issue is I need the WD19DC due to the other peripherals I have connected.  I researched in detail the specifications of both the docking station and the WX7100 GPU on the motherboard in order to make sure it worked how I needed it.  It worked, for a few months, then I hit the 60Hz sync problem which involved Dell replacing multiple docking stations (and some hilarity about replacing DP cables).  This didn't resolve it.  Eventually swapping the motherboard in my laptop (i.e. also a new GPU) did fix it, albeit through losing my TPM and having to materially rebuild my laptop crypto.  I am looking for a better understanding of the problem as there are plenty of other Dell Precision laptop owners out there with a similar problem.

Didn't have these issues with my last workstation laptop, with Nvidia GPU. I'd rather not go back to Nvidia.

[fsadough]

I have the WD19DC myself on my desk connected to 2.5K monitors and once in a while I see similar issues like you. If you have no issues connecting directly to the laptop, it rules out the failure on GPU side. I suggest you file a ticket with DELL, try to update the thunderbolt driver along with system BIOS

Guide to Dell Docking Stations | Dell US 

[garf]

Yeah, the Dell crew pointed me towards the Thunderbolt drivers, a specific version 40.1 IIRC, and firmware that wasn't provided via their support site.  Everything I have is at the absolute latest ersion provided by Dell.  Updating those made no difference.  As for direct connection ruling out GPU problems, I am not so sure.  Replacing my motherboard had the side effect of resolving the problem last time.  The GPU passthru over the dual USB-C Thunderbolt interfaces may have different electrical connections and timing which could conceivably "bother" the bit rate calculation, hence my question on how to find out what the GPU is "seeing" when I connect a DP monitor to the WD19DC.  I am prepared to put effort into establishing what the problem is, however with proprietary drivers and without assistance that is harder than I think it needs to be.

I am at the point of raising a support ticket with Dell and taking them straight to "new motherboard please" pointing to my previous ticket.  This is a huge bother for me, as my TPM is wiped.  Several TB of Bitlocked drive to decrypt before I can do that.  Appreciate the discourse here, and reassuring to know you have access to a WD19DC also.

Thanks.

[fsadough]

1. Get a USB-C to DP cable and connect one of your monitors to it and see how it behaves:
   https://www.amazon.com/DisplayPort-uni-Thunderbolt-Compatible-More-Gray/dp/B075V27G2R 
   

[garf]

Not sure how that will help.  WD19DC manual states that ONLY the Display Port outputs are capable of 4k @ 60Hz.  The USB-C and HDMI ports cannot be used.

Using either of the Thunderbolt ports on the laptop means I can't connect my docking station.  Not a configuration that is helpful to me.

[fsadough]

You were indicating:

The GPU passthru over the dual USB-C Thunderbolt interfaces may have different electrical connections and timing which could conceivably "bother" the bit rate calculation, hence my question on how to find out what the GPU is "seeing" when I connect a DP monitor to the WD19DC. 

Now to find out if you get a different timing from USB-C output =>

1. disconnect your laptop from docking station 
2. Connect 1st BENQ monitor via mDP-DP Cable (mDP output from your laptop)
3. Connect 2nd BENQ monitor via USBC-DP Cable (USB-C output from laptop)

If you don't see any issues, then you can be sure that problem is related to your docking station.