XPS 9360 missing resolution

What dock, cable, and/or adapter(s) are you using in order to connect that display to your XPS 13 9360?  And how does that compare to how you connect that display to the other PCs you're testing with?  What GPU and driver version are those other PCs running?

cable HDMI 2 on all cases

for the Dell XPS13, the dock is USBc Targus ACA 921.

Dell XPS13 GPU Iris 640, driver: 22.20.16.4735

Through the same dock or directly the same HDMI cable.

Thanks

You didn't specify what GPU and driver version the OTHER laptops you were testing the display with are running. Or are you testing multiple identically configured XPS 13 9360s and only seeing this issue with one of them?

I'm betting this is a driver or firmware issue, perhaps one that only appears with this specific display, because from the system's perspective, its GPU is sending native DisplayPort from USB-C, and then your Targus adapter has a DisplayPort to HDMI active converter chip, which the XPS would not have any control over or even realize is there.  My guess is that this chip is somehow affecting the EDID data that the display is providing to the system, which is what tells the system about the display's specs, including what resolutions the display supports.

And on an unrelated note, I wasn't able to find the Targus ACA 921, only an ACA 929.  But just so you know, if your adapter has both display outputs AND a USB output, then its display bandwidth will be half of what's available from the USB-C port. This means you would be limited to 4K @ 30 Hz, whereas if you used an adapter that was only USB-C to HDMI, you could get 4K @ 60 Hz, assuming the P2715Q accepts that signal over HDMI.  I wrote a detailed post explaining the reason for this difference in adapter capabilities here if you're curious: en.community.dell.com/.../20017807

Hi,

I did not specify models, because this is the only one I have with Iris. All the others have some kind of Nvidia or AMD. I think one was with intel HD but not sure.

You are indeed correct that I can only have 4k@30Hz, but it runs smooth.

The issue I m having while on 4k is with the DPI scalling of the applications which is terrible on many applications, even Office2016 looks a bit off.

So, the 2560x1440 is the best solution for me at the moment, (unless Microsoft works miracles on DPI scaling ).

Since the custom resolution works , and technically the settings I want are not above the limits of the monitor/cable/GPU, I should be able to have that resolution.

Thanks for your interest on my issue.

I agree that you shouldn't have to have a custom resolution.  Again, my guess is that this is caused by some combination of your driver, that adapter, and your display.  That driver certainly shows 2560x1440 on other displays, which is why I think it's this specific combination of hardware and driver.

In terms of scaling, Windows does have challenges when multiple displays with very different pixel densities are used simultaneously -- and in fairness, so does Mac OS.  The reality is that it can only fully optimize for one pixel density at a time.  Scaling has been getting progressively better with newer versions of Windows 10 (especially the latest Creators Update), but it's still not perfect, and a big part of that is that even though Microsoft is providing new scaling mechanisms, applications have to actually support them, and if an application is still using legacy scaling mechanisms, it won't benefit as much or at all from OS-level improvements.  I'm surprised even Office 2016 is problematic though!

One experiment you can perform if you haven't already would be to set your 4K display (running at 4K resolution) as your primary display, and then log off and back onto Windows, since some scaling changes don't take effect until a logoff/logon cycle.