Hello, I am using a CAC-1567 to connect a Latitude 7420 to an LG 35wn65c-b with a CLUB 3D Displayport 1.4 cable. This only works intermittently, often not showing any video or a corrupted output (attached). I've updated all drivers and firmware, and tried different refresh rates with no success. I'm trying to run the monitor at 3440x1400 at 100hz, which works fine from my desktop and occasionally through the laptop and adapter. Appreciate any ideas on how to resolve this.
Are you able to test the adapter on a different laptop? This way you may be able to rule out if the adapter is defective or not. It does work correctly from PC with the CLub 3D cable, the cable is not at fault.
Do you have any other peripherals connected to the notebook? Try to test with out anything but the adapter.
Also have a look at the power savings settings on the USB ports.
Thanks for the advice. Unfortunately I don't have another USB-C device to test.
In order to get the display to work, I need to open and close the laptop a number of times (which re-detects the monitors). Eventually it displays properly and stabilizes. I've also tried another brand USB-C to DP cable (not adapter), that actually had slightly worse results and either took more tries to work right or was not stable.
I tried changing all the USB ports to not turn off to save power in device manager, no effect.
Any other ideas?
HDMI works, but then I cannot use my DP KVM and TB4 dock. Just a note, the issue happens if I go through the KVM/Dock or connect directly to the monitor.
I did discover that if I force the setting in the monitor to DP 1.2 mode, everything works normally. This is enough for 3440x1440 100hz, I just lose the ability to do HDR, which isn't critical at this time.
This makes me wonder if there is an issue with DP 1.4 implementation on either the monitor or the laptop. The laptop hardware is Iris Xe which should be ok. I've updated all drivers/firmware as well. The Laptop is running windows 10, not 11, but I don't think that would be the issue.
Sorry to confuse. The KVM works fine with HDR, it's a DP 1.4 KVM. The problem I described occurs with or without the KVM in the mix. The CAC-1557 is between the TB4 dock and the KVM, or for testing, between the Laptop and the monitor.
So even with the laptop connected directly to monitor, it will not reliably connect on DP 1.4. I have to plug/unplug or open and close the laptop to get it to redetect the monitor a number of times, eventually I get lucky and it works. If the monitor goes to sleep, I have to go through it all over again.
Now, if I force the monitor to DP 1.2, it all connects and works normally, just with the inherent limitations of DP 1.2.
Sounds like you are having the issue with or without the TB4 dock and also with or without the KVM. Basically, in all of these cases, you have a problem:
I guess the only thing you haven't tried is shorter cables or a different computer?
Is there someplace in Windows that indicates the DisplayPort link rate to the display? I believe GPU-Z shows the link rate for AMD or Nvidia GPUs in the Advanced tab. I'm not sure about Intel GPUs.
DP 1.2 uses HBR2 link rate. HBR2 link rate is sufficient for HDR (10bpc) with 3440x1440@100Hz but maybe the display doesn't indicate HDR support in the DP 1.2 EDID?
What if you force HBR2 link rate from the computer without switching the display to DP 1.2 mode? To do this, connect a DP 1.2 MST hub such as the CSV-6400.