External monitor not working with laptop via DP/USB C and limited to 40Hz on HDMI.

[btew87]

1. My external monitor is not working when using USB C to Display port. It is not recognised at all and remains black screen.

2. The monitor does work with the HDMI cable but is limited to 40Hz refresh rate. The max resolution of 3440x1440 was attainable only using the Intel Graphics Command Center by adding a custom setting. This was not possible to do via windows 10 settings.

Is there something I can try to get point 1. working?

I have tried:

• Uninstalling USB host controller and USB devices in windows device manager and rebooting.
• Using a different display port to usb c cable.
• Testing the display port/ usb c cable with a different 34" HP 3440x1440 monitor (laptop didn't recognise it either).
• Selecting DSP1 and DSP2 when the cable is plugged in via the monitor.
• Disconnecting all other peripheral devices and booting with just the cable and laptop charger plugged in.

For point 2. I have tried different HDMI cables but it seems limited to 40Hz. Ultimately getting the display port to USB C option is the what I'm trying to achieve. To get 40Hz+ I believe I need a HDMI to display port adaptor as per n_scott_pearson's post:

https://community.intel.com/t5/Graphics/How-to-get-3440x1440-60hz-on-Intel-HD-620-Graphics-Card/td-p/1211556

My specs are as follows:

OS: Windows 10 (up to date)

Monitor: AOC CU34G3S/BK (34", 3440x1440)

Laptop: ASUS X509FA

Laptop USB port used: USB 3.1 Gen1 Type-C

Cable used: uni USB C to DisplayPort Cable 1.8m(4K@60Hz, 2K@165Hz) Thunderbolt 3/4 to Display Port Cable, Aluminum 144Hz DP Cable.

Laptop graphics chip: Intel UHD 620

Graphics driver: igfx_win_101.1960 (latest)

[megan3000 · Accepted solution]

You may start installing the graphics driver from Asus. I can see you're using latest one from intel, which may make your laptop lose customizations... the asus one is on their website

https://www.asus.com/Laptops/For-Home/Everyday-use/ASUS-X509/HelpDesk_Download/?model2Name=ASUS-Laptop-15-X509FA

However, first thing to do is, are you sure your laptop's USB- C can output video? Some USB-C port are only design to provide data transfer and power for regular devices (and not for non-display devices)

Based on Asus website (I used the model you provided) it comes with the simplest USB-C port, which is a USB-C 3.1 allowing only 5Gbit/s transfer rate, which is not enough to provide the required bandwidth for common resolutions over displayport like WQHD/QHD@60Hz or 4K@30/60Hz... this would be very rare because 5Gbit/s will only allow, let's say... 1080p@60Hz... this "design decision" is not common for USB-C ports using DisplayPort Alt mode.

https://dlcdnets.asus.com/pub/ASUS/nb/X409FA/0409_E15108_X409_X509_A.pdf

I couldn't find any statement, indication, or clue that would make one think that this laptop for sure supports video output via USB-C

https://www.asus.com/Laptops/For-Home/Everyday-use/ASUS-X509/

https://www.asus.com/support/FAQ/1042843/

For issue # 2, what refresh rate are you trying to set? If you wish to set 3440x1440@60Hz let me tell you that your laptop is limited with an HDMI 1.4 port...

the digital bandwidth required for 3440x1440@60Hz is in the very very very edge or limit of what is (in theory) supported by HDMI 1.4 protocol... However, my experience has shown me that manufacturers may sometimes even limit more the "bandwidth capabilities" on HDMI ports... It doesn't matter if your monitor has DP1.4 and HDMI 2.0, or if you're using super-high-speed 4K cables... you may be just restricted by the HDMI port on your laptop...

[btew87]

Thanks for you informative reply, megan3000.

Accessing the ASUS links you provided, for my particular laptop and the USB 3 port is not capable of display output. I only have the "SS" symbol and the USB logo next to the port and not the "D" symbol which would imply display out. My HDMI version is 1.4 so again not compatible with 3440x1440 @60Hz as bandwidth is too low.

The modern USB naming conventions can be confusing as well with USB 3.1 Gen1 also being USB 3.2 Gen 1:

https://www.cnet.com/tech/mobile/usb-3-2-explained-making-sense-of-current-and-confusing-usb-standard/

I'm happy with the 3440x1440 @40Hz for the time being as it's a work machine although I'm surprised that the refresh rate of an extra 20Hz is not achievable yet the full res of 3440x1440 is (via HDMI 1.4). I'll have to upgrade my laptop for the extra display performance.

I have seen some sites state that 4K @60Hz is attainable via HDMI 1.4 but I think it involes understanding Chroma Subsampling and a few other things like the bandwidth limiting you mention which might be preventing mine from being able to do it. I don't know enough about these things and is probably outside the scope of what most people look for when it comes to buying a laptop.

[ZoranG]

ASUS ZenBook Pro problem connecting via USB C port to external monitor

Hello, I am using the ASUS ZenBook Pro for years without problems, using also external monitor via HDMI cable. Now I am trying to connect second external monitor with HDMI/RGB/DVI input via USB-C and I also bought a USBC to HDMI cable that says it is able to support up to 4k 60hz. However, when I connected using the USBC, the monitor is detected by WIN10 correctly as 2nd external monitor but monitor is mostly black with occasionally flickering with extended Windows background on it. Restarting Windows many times, detecting monitor, on/off monitor, update all Asus drivers... The same HDMI cable also work fine via nearby HDMI port to the 1st external monitor,

I tried using the USBC to HDMI cable on my mac which has a thunderbolt as it works and display works fine, so I don't think it is the cable's fault. Does the ASUS ZenBook Pro not support external display via USB C or something?