HP ProBook 450 g9 USB-C Dock stuck at 4k30

[waym77]

Hi,

I have a HP ProBook 450 G9 which I am trying to connect to my Targus DOCK423EU.

The key problem is I'm trying to connect 2x 4K60hz displays to this dock but both external monitors cannot go higher than 4K30hz.

The Targus websites specifically says it supports 2x 4K60 over its 2x HDMIs using DP alt mode

The HP website says this laptop supports DP alt mode over its SuperSpeed USB Type-C® 10Gbps signaling rate (USB Power Delivery, DisplayPort™ 1.4).

The cables were separately tested at 4K60hz and do work for that.

The dock is powered by a 100W USB-C adapter.

The Iris Xe drivers are up to date.

But I am only getting 4K30z in settings.

I did turn on High resolution while docked in the HP bios, no change.

Any help would be appreciated, thanks!

[banhien]

@waym77 

People keep buying cheap and un-supported  dockst. I would NOT buy third party products until HP (or Dell or Levono) has time to test all of them and confirm which ones are compatible.

HP is going to do that ? I don't think so. You have to ask Targus: Did they test their docks with HP machines - which ones work and which ones don't

Regards.

[Jupitero]

Hello.

Could you please include the monitor model numbers?

If you plug one monitor to the laptop internal HDMI port do you then get 4k on either / both screens?

[waym77]

Hi,

They are 2x Samsung 43QN90B TVs, they work fantastic with my other computing devices. These displays are capable of 4K 144hz but for this purpose they would run at 4K 60hz from the HDMI ports.

Plugging one monitor directly into the laptop's HDMI port gives me 4K60hz as required but in this case (one HDMI into the laptop, one in the dock), the dock is still outputting at 4K30hz.

If I try to connect only one display to the dock (leaving the other completely disconnected), I still only get 4K30hz (meaning I don't think DSC is the issue).

[Jupitero]

Hi,

I'm still thinking this could be a bandwidth issue. Can you try limiting the HDMI input in Samsung to 8-bit color mode? 10-bit or 12-bit color requires more bandwidth. Targus has a "Compatibility Application Note" page where HDR10 is mentioned to work with only one 4K display at a time.

The Intel Graphics Center can be used to limit color space to 8 bits, and also the chroma subsampling can be lowered from RGB/4:4:4 to 4:4:2 to 4:2:0.

If you have other laptops compatible with this Targus dock you should try them as well. It would be great to find at least one combination where a computer can drive 2x 4K displays @60hz!

Another thing - you mentioned enabling the "High Resolution mode when connected to a USB-C DP alt mode dock" setting, and it did nothing. Check that the setting is still enabled, and try the HP power reset procedure as well - just in case the setting didn't take. (a long shot this one)

You should be able to verify with a fast USB drive that something did happen if you can transfer data beyond USB 2.0 speeds. (the setting limits USB functionality to this level)

[waym77]

Hi,

Thanks for the detailed response, however I did find the solution.

It was within the display, for some reason when connecting HDMI via dock it kept the HDMI at standard instead of enhanced (it switches this automatically when connecting directly, which is why I didn't think of this).

Now I'm able to operate at 2x 4K60.

[Jupitero]

Hi,

That's great news!