Dell monitor 'blinks', HD 6870 (video inside)

[noambbv]

Hey,
I have a Dell U2515H 1440p that doesn't get along with my pc. (although the monitor itself isn't faulty)
My Graphics card is Radeon HD6870 (2xmDP,2xDVI,1xHDMI). Dell is connected to mDP, and my other monitor is connected to DVI 1080p.
The problem is that the monitor becomes black for ~2sec, then returns, and after some various time, it blinks again.
It began the very minute I plugged the new Dell monitor to my pc. The 1440p monitor just blinks randomly.
Sometimes it blinks once in a few minutes, other times twice a day, and often it blinks so much that it's completely unusable.

I uploaded 2 demonstration videos of the issue, because I had no idea how else to describe it.
The other 1080p monitor has never suffered from this issue ever, only the new Dell from day 1.

In the other video I jumped into the menus to show you guys that I'm running the monitor under DP1.2 (default was 1.1), and suddenly it blinked, and then blinked again.

The monitor and cable are fine, for I don't have any issues with the monitor under Windows 10. Only OS X makes the monitor blink. I tried connecting the Dell through HDMI, and same result. (although as I recall, I had no option for 1440p when connected via HDMI).
In 'About This Mac' it doesn't fully recognize the video card ("AMD Radeon 6xxx Series"), but I can play the Chess app, so framebuffer shouldn't be the issue (?).

After much research, I read about a few others who had had similar issues, but nobody had a solution.

Any help would be appreciated, Thanks!

 

[VioletDragon]

Hey,
I have a Dell U2515H 1440p that doesn't get along with my pc. (although the monitor itself isn't faulty)
My Graphics card is Radeon HD6870 (2xmDP,2xDVI,1xHDMI). Dell is connected to mDP, and my other monitor is connected to DVI 1080p.
The problem is that the monitor becomes black for ~2sec, then returns, and after some various time, it blinks again.
It began the very minute I plugged the new Dell monitor to my pc. The 1440p monitor just blinks randomly.
Sometimes it blinks once in a few minutes, other times twice a day, and often it blinks so much that it's completely unusable.

I uploaded 2 demonstration videos of the issue, because I had no idea how else to describe it.
The other 1080p monitor has never suffered from this issue ever, only the new Dell from day 1.

In the other video I jumped into the menus to show you guys that I'm running the monitor under DP1.2 (default was 1.1), and suddenly it blinked, and then blinked again.

The monitor and cable are fine, for I don't have any issues with the monitor under Windows 10. Only OS X makes the monitor blink. I tried connecting the Dell through HDMI, and same result. (although as I recall, I had no option for 1440p when connected via HDMI).
In 'About This Mac' it doesn't fully recognize the video card ("AMD Radeon 6xxx Series"), but I can play the Chess app, so framebuffer shouldn't be the issue (?).

After much research, I read about a few others who had had similar issues, but nobody had a solution.

Any help would be appreciated, Thanks!

Are you using any Adaptors that are active adaptors not passive adaptors. Be sure that the Cable is not damaged in anyway. How are you (Injecting ATI)?

 

[Fl0r!an]

Try to inject the "Duckweed" framebuffer and report back. It should match 4 out of 5 ports (2nd DVI will be dead).

 

[noambbv]

Are you using any Adaptors that are active adaptors not passive adaptors. Be sure that the Cable is not damaged in anyway. How are you (Injecting ATI)?

I'm using the mDP to DP provided by Dell. No way it's damaged, I've been running Windows 10 for months with no issues whatsoever. And I also tried HDMI to HDMI and the same result.

Try to inject the "Duckweed" framebuffer and report back. It should match 4 out of 5 ports (2nd DVI will be dead).

First, I only added 'Duckweed' and there was no change (6xxx in about this mac, and blinking)
Then, I checked the V on 'Inject ATI', and now the card is recognised as 6870, but there's still blinking... I tried switching the [mDp to Dp] cable to [HDMI to HDMI], 1440p wasn't showing up, and there were blinking as well.

(The blinking is only on the Dell monitor)

I uploaded a screenshot of About This Mac after ticking Inject ATI and writing Duckweed.

Thank you sooooo much for helping

 

[Fl0r!an]

Strange. I'm using the same display on my Hack, and I've used it with numerous GPUs in the past, and neither of them exhibited this behavior.

Does anything change if you unplug your 2nd display?

 

[noambbv]

Strange. I'm using the same display on my Hack, and I've used it with numerous GPUs in the past, and neither of them exhibited this behavior.

Does anything change if you unplug your 2nd display?

EDIT: 30 seconds after posting this while I was thinking my Dell is functional, it started blinking again...
I'll try disconnecting my other monitor, but I already tried that before. Im hopeless (

EDIT 2: unplugged 2nd display, and still experienced blinks.

 

[VioletDragon]

I'm using the mDP to DP provided by Dell. No way it's damaged, I've been running Windows 10 for months with no issues whatsoever. And I also tried HDMI to HDMI and the same result.


First, I only added 'Duckweed' and there was no change (6xxx in about this mac, and blinking)
Then, I checked the V on 'Inject ATI', and now the card is recognised as 6870, but there's still blinking... I tried switching the [mDp to Dp] cable to [HDMI to HDMI], 1440p wasn't showing up, and there were blinking as well.

(The blinking is only on the Dell monitor)

I uploaded a screenshot of About This Mac after ticking Inject ATI and writing Duckweed.

Thank you sooooo much for helping

You have this problem in Windows as well as OS X?

 

[noambbv]

You have this problem in Windows as well as OS X?

Never in Windows, only OS X

 

[VioletDragon]

Never in Windows, only OS X

Strange. Im using a 6870 in OS X with 3 monitors. Are you injecting via a DSDT? or just using Clover to inject?

 

[noambbv]

Strange. Im using a 6870 in OS X with 3 monitors. Are you injecting via a DSDT? or just using Clover to inject?

Just clover, but I think I built a DSDT to make audio work though.