4K monitor black screen during post over DP


Limp Gawd
Oct 28, 2014
I have had a issue with all 4K monitors that I owned and it's driving me a bit nuts so I wanted to see if somebody has a solution.

When I cold boot the PC the monitor shows picture during POST so I can enter the BIOS or see the boot menu.

But 99% of the time when I restart PC the monitor does not get any signal and goes in to sleep mode, what I must do is press ctrl alt del to restart again before it boots into Windows for the monitor to receive a signal and picture to show on screen.

This is a displayport issue as I tested with a HDMI cable and it does not happen but since the monitor is not HDMI 2.0 I only get 30Hz at 4K :/.

I was Googling about this issue and found something on a page named "Issues you may encounter using the UP2715k Dell UltraSharp 27 Ultra HD 5K Monitor"

Cannot see POST screen (Boot-up screen) when cold boot or restart computer. This is due to slow recovery and connection time of the monitor.

If accessing POST screen is critical, please connect to another monitor (non-4k, non-5k) and restart system.

While that is about 5K monitor I believe it's the same issue on 4K monitors,"slow recovery and connection time of the monitor".

Could a DP to HDMI adapter be a solution? Or maybe a better quality (more expensive) cable?
OMG, the solution solution is found and it's so simple, just setting DDC/CI to OFF. I had it in front of me all these years, :facepalm:.


Maybe this also solves the windows resizing problem in Windows when monitor is turned off and back on.

Edit: Forget what I wrote, it doesn't work. After setting the switch I rebooted several times and it did show picture every single time but after using Windows for 2 hours and testing again, now it goes to sleep again every time I restart :(

Edit 2: After reading this I ordered a Amazon Basics DP cable where pin 20 is not wired, I also ordered a Belkin VESA compliant cable to try.

But after I ordered these cables I tested if the issue happens when using iGP, so I connected DP cable to the motherboard and rebooted several times and the monitor did not lose the signal even once, so this is not a problem with the built in graphics. I remember having the issues on both AMD and Nvidia cards.
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It sounds like there's a chance the new cable will fix it. Which video card do you have?
Palit GTX 1070 JetStream, but the thing is that I experienced the same issue when I had a AMD card and I experienced the issue on all 4K monitors that I owned and that's 3 of them including this one. I have had different PCs during these years, with Z87 and Z107 chipset so it's also not anything specific to the current system I use.

I was hoping new cables might do it hence why I ordered two new with different lengths to try but since it does not seem to happen when monitor is connected to iGP I start to doubt that the cable could help but will find out in a few days.
I can happily report that the 3 feet AmazonBasics cable seems to have solved the issue, maybe a bit too early to celebrate but so far after a few restarts the monitor showed picture every time.
So maybe it is pin 20 on those non compliant cables creating issues. This cable is cheap and good, better then those overpriced Monster cables which probably are not VESA compliant.