Did you read through this and test the MST Modes using both cables? What revision is this monitor?

I had read through the mentioned page.

My video card supports DP1.2 and MST is/was off in both cases.

This monitor is revision A03.

Before you get the monitor exchanged, I would test it on another computer to see if the issue follows the monitor. If the issue is not on the other computer, the monitor is not the culprit.

Hi Chris,

I am just back from vacation. Unfortunately I do not have another computer on which I could test that.

Since the cable seems to have an influence (i.e., Dell cable seems to allow 60Hz with black screen coming at intervals vs ability to only reach 30Hz with the other cable), would it be possible to perform another test with a Dell DP-to-DP cable (instead of the m-DP to DP cable that was included with the display)?

Best regards,

Christophe

Not sure. Does the video card have multiple DP out ports to test?

The video card has only one DP to test.

Now I just found an AMD "GUIDE TO 4K DISPLAY CONNECTIONS" where it is stated: "AMD recommends using DisplayPort 1.2 certified cables with a length of 2m (~6 ft) or less when driving 4K monitors.".  I wish I had read it before I ordered my StarTech 3m DP to DP cable. I would have ordered a 1 meter one instead.

I just got a 1 meter StarTech cable which is shorter than the Dell mDP to DP cable. Now with that cable I can select 4K @ 60 Hz. However when I do so the screen stays black.

The monitor goes black and the only way to go back to MST > Off is to use the plug the Dell mDP to DP cable and access use the OSD.

Note that now also with the Dell cable with MST > Off and 4K @ 60 Hz the monitor goes black.

Is there anything special with the Dell cable DP cable? Could I get a shorter Dell DP to DP cable?

What else do you suggest?

Nothing special about the cable, just a standard. No, we only have the 6'. Before getting a monitor exchanged, I would find another computer to test this monitor on.