Dell U2515H: Native resolution distorted

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Dell U2515H: Native resolution distorted

I recently purchased a Dell U2515H monitor. I want to use it with my MacBook Pro 13'' 2012, non-Retina, 2.5GHz. According to the tech specs, this MacBook can drive a single 2560x1600 pixel display (http://www.apple.com/macbook-pro/specs/).

However, for me, it fails.

I tried two different DisplayPort-cables, one came bundled with the screen. Running the display at 2048x1152 pixels (the second highest resolution) works fine. For the full resolution, OS X preselects 59,956Hz, I can't change that.

I tried under Bootcamp Windows 10 on the same machine, and the display works fine under 2560x1440.

Any idea what to do?

MacBook Pro (13-inch Mid 2012), OS X El Capitan (10.11.1), Samsung SSD 850 Evo

Posted on Nov 15, 2015 4:30 AM

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Answer 1

senthor Author

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Nov 15, 2015 6:56 AM in response to senthor

Okay, it get's really weird.

When I boot the Recovery Partition, the display works fine.

When I reinstall OS X, everything works fine while installing, but after the final reboot the screen get's distorted again.

Seems like a really weird software issue. Will try a clean install on external drive next.

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Answer 2

Nov 15, 2015 7:12 AM in response to senthor

This sounds like a known OSX issue when connecting to some external monitors, so reinstalling might not solve the problem. This link contains a script (at the top) you can modify to your monitor, but you might need a few tries: http://embdev.net/topic/284710

Good luck!

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Answer 3

senthor Author

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Nov 15, 2015 8:57 AM in response to Nordic Pioneer

Hi,

I read about this, and tried it, but it doesn't help. The issue is not the image being a YPbPr stream.

I took some screenshots of the visible area and found one thing: The visible area has the dimensions of 256*720 pixels, being 1/10 of the width and 1/2 of the height. I also found out, that these 20 pieces if the images are stacked on top of another. So it seems like there are synchronization issues or problems with the DisplayPort stream.

Help! 😐

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Answer 4

Nov 15, 2015 9:37 AM in response to senthor

Ok, I understand it much clearer now. But you write the image on the monitor is correct when selecting a lower resolution and booting from the limited OS-support provided from both the recovery partition and the installer. These observations shows it's not a hardware issue, but most likely related to when OSX activates the files containing the parameters controlling the built-in video adapter.

The link I posted showed that the actual video stream from the adapter to the monitor can send less than optimal signals. Have you considered using a HDMI High Speed cable instead of DisplayPort?

BTW: Which version of OSX are you running?

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Answer 5

senthor Author

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Nov 16, 2015 1:37 AM in response to Nordic Pioneer

First things first: Thanks for your help 🙂

I'm running El Cap (10.11.1). I can give the HDMI solution a try, but I will have to buy a cable first. Is there anything special I should be looking for? I can't find a Mini-DP to HDMI High Speed cable.

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Answer 6

Nov 17, 2015 9:47 AM in response to senthor

So your Macbook Pro doesn't have HDMI output, only Mini-DisplayPort? I only suggested it since on my MBP Retina 2012 with HDMI I had to use HDMI output and correct the linked EDID-file to get a proper connection from OSX.

When your hardware connects properly in Windows 10 it's more than likely the solution you want will be found in the configuration/modification of the EDID support. Combining the information from the embdev.net site with the correct code your monitor will probably manage to show a correct and undistorted image from OSX. I'm sorry but there were no easy solution available when I searched for it as of today.

Good luck anyway! 🙂

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Answer 7

senthor Author

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Nov 23, 2015 7:29 AM in response to Nordic Pioneer

Ok, so what I found out, the connection parameters are different when running the machine under Windows. I tried using SwitchResX to get the same value as under Windows, but the values are not accepted... The scan rate is always changed while saving the settings, it should be 88,786 kHz / 59,95 Hz, however it get's changed to 88,787 kHz / 59,94 Hz. The image does look different when saving this, but not good. So now I want to try to manually create an EDID override, any idea how to achieve this?

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Answer 8

Nov 24, 2015 6:47 AM in response to senthor

You now need the link I posted on Nov 15: http://embdev.net/topic/284710

It contains the workaround for monitors the OS interprets incorrectly, and tells you how to create the manual override in question (however buried in the thread). The only difference between the instructions in that link and your actual need is the parameters you need to tweak.

But I think there is a slight chance of a second option, and that is a physical EDID emulator. But I'm not sure if these are made for DisplayPort at all.

I'm sorry I can't point you directly to an easy solution, but this is a roundup of the options left (unless I've overlooked some signinficant info during the thread).

Please notify us if you can get closer to a solution with the URL posted at the top. Good luck! 🙂

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Answer 9

Nov 28, 2015 3:58 AM in response to senthor

Oh ****. I have a macbook pro mid 2012 15" and I was planning on buying this monitor.

I dont know if I should go ahead now...

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Answer 10

senthor Author

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Aug 3, 2016 4:37 AM in response to senthor

Oh, I forgot to resolve the thread.

I reinstalled OS X and migrated from a Time Machine backup, now everything works fine.

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