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

[VioletDragon]

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

Attach config and DSDT. Ill have a look for you.

 

[noambbv]

Attach config and DSDT. Ill have a look for you.

Hey, Thank you so much for helping out!
Sorry for the delay, I changed the config.plist SMBIOS from iMac to Mac Pro,thinking it would help, but I was wrong, and then I changed it back again to iMac so you could have a look
As it seems, I actually don't have a dsdt but rather have the FixHDA flag on, and this is what fixes my audio. So I only uploaded the config.plist

Thank youuuu

 

[VioletDragon]

Hey, Thank you so much for helping out!
Sorry for the delay, I changed the config.plist SMBIOS from iMac to Mac Pro,thinking it would help, but I was wrong, and then I changed it back again to iMac so you could have a look
As it seems, I actually don't have a dsdt but rather have the FixHDA flag on, and this is what fixes my audio. So I only uploaded the config.plist

Thank youuuu

Try this config with a DSDT. FYI there is a DSDT for you're motherboard in DSDT Database make sure that you select the correct DSDT for your BIOS version. DSDT goes in EFI/Clover/ACPI/patched/DSDT. Report back if any issues.

 

[noambbv]

Try this config with a DSDT. FYI there is a DSDT for you're motherboard in DSDT Database make sure that you select the correct DSDT for your BIOS version. DSDT goes in EFI/Clover/ACPI/patched/DSDT. Report back if any issues.

Ok, my Bios version was FB so I updated it to FK, then changed my bios settings to as they were before the update.
Then I downloaded the dsdt, changed its name to DSDT.aml and moved it to where you told me.
I also ticked off all the V in 'fixes' such as FixHDA, because they wouldn't be necessary since I have a dsdt now.

The thing is, now my USB ports are not working after Clover, so I'm stuck at the login screen. This is a weird issue, Ive never had a no usb problem before.. maybe its caused by the dsdt ? My mouse and keyboars work great in the clover menus.
I also rebooted into a Yosemite backup, and ticked 'Fix Usb' for my ElCap, to no avail

And the blinking problem is still here :/

 

[VioletDragon]

Ok, my Bios version was FB so I updated it to FK, then changed my bios settings to as they were before the update.
Then I downloaded the dsdt, changed its name to DSDT.aml and moved it to where you told me.
I also ticked off all the V in 'fixes' such as FixHDA, because they wouldn't be necessary since I have a dsdt now.

The thing is, now my USB ports are not working after Clover, so I'm stuck at the login screen. This is a weird issue, Ive never had a no usb problem before.. maybe its caused by the dsdt ? My mouse and keyboars work great in the clover menus.
I also rebooted into a Yosemite backup, and ticked 'Fix Usb' for my ElCap, to no avail

And the blinking problem is still here :/

Did you Drop OEM_DSM in Config.plist? Im really not sure what that blinking problem could be.

 

[noambbv]

Did you Drop OEM_DSM in Config.plist? Im really not sure what that blinking problem could be.

Tried both and no USB + goes black sometimes..
I'm not alone in this - Googling "U2515H blinking" / goes black yields a noticeable amount of people with a similar issue, yet nearly not as many solutions.

Could it be that my graphics card driver needs some sort of a tweak, supplied by the Windows version, which the Mac version lacks? Have a look:
http://en.community.dell.com/support-forums/peripherals/f/3529/t/19626679

Especially a reply that caught my attention:

I did the exact same you did. Ordered 2 new DP cables and threw away the mDP cables that came with the monitors. I connected the first cable from my ATI Radeon HD6870's DP port to the DP "In" port of the first monitor and with the second cable I connected the DP "out" port of the first monitor to the second monitor on DP "in". Alas, that didn't work neither.

By the way, I'm using two Dell U2715H monitors, both Rev. A00.

I've tried for weeks to get the MST working and finally things are looking good. It seems to be working fine now using the standard mDP to DP cables too. The first monitor has DP 1.2 enabled, the second doesn't.

What I did:

I was thinking of trying to download and test some older Catalyst drivers from the manufacturer's website.

I'd downloaded all versions there were available, back to 2011.

Before each new installment of the Catalyst drivers I used the driver cleaning tool from AMD. That one is called: "amd_cleanup_util_1.2.1.0.exe".

Eventually I'd installed Catalyst driver V. 14.1 (13.251.0.0 WHQL) for Windows 7 64-bit. That version seems to work fine now. No black screen for a moment or whatsoever.

I did the installation using only one monitor connected and had DP 1.2 disabled.

An Important notice is that when the Catalyst installation program was complete and it asked for a reboot I clicked no and closed down Windows myself. I then daisy-chained to the second monitor and enabled DP 1.2 only on the first monitor. Then I did the reboot.

It's working prefectly fine now as I'm writing this, I only hope it will stay this way. And that will be about time too because I bought these screens in January and it this is the very first time they are working without any trouble.

Sigh..... I hope this helps for all you with the same problems. Good luck!

Maybe the current driver fixes it in Windows, and that's why I'm not experiencing this in Windows.. at least that's my theory. :/

Do you have any other idea?

 

[VioletDragon]

Tried both and no USB + goes black sometimes..
I'm not alone in this - Googling "U2515H blinking" / goes black yields a noticeable amount of people with a similar issue, yet nearly not as many solutions.

Could it be that my graphics card driver needs some sort of a tweak, supplied by the Windows version, which the Mac version lacks? Have a look:
http://en.community.dell.com/support-forums/peripherals/f/3529/t/19626679

Especially a reply that caught my attention:


Maybe the current driver fixes it in Windows, and that's why I'm not experiencing this in Windows.. at least that's my theory. :/

Do you have any other idea?

It maybe a Frame Buffer issue. Which 6870 do you have? Try not injecting and boot into OS X but make sure you boot without cache. Do you have another monitor to test?

 

[noambbv]

It maybe a Frame Buffer issue. Which 6870 do you have? Try not injecting and boot into OS X but make sure you boot without cache. Do you have another monitor to test?

My HD 6870 is Gigabyte's
I discovered something very interesting.
mDP/HDMI -> Dell monitor has 3 constant blinks, at the same locations, at POST. I didn't notice those until now because they were well placed.
I have a DVI to HDMI cable which I started playing with: DVI connected instead of my 2nd monitor. The cable itself becomes HDMI, which I connected to my Dell monitor. Then I didn't have any blink during boot time (at POST). It was really smooth.
For some reason I can't output 1440p with this cable though. But I think this is a lead to the solution.
I can upload a comparison video if you'd like.

Anyway, I restored my ElCapitan to before the dsdt which disabled my USB ports, and booted without cache, and no blinks so far, but it's been running only for a couple of minutes so I can't be sure.
EDIT: Rebooted again with no cache and it started blinking again But we do have a lead, so that's something

 

[VioletDragon]

My HD 6870 is Gigabyte's
I discovered something very interesting.
mDP/HDMI -> Dell monitor has 3 constant blinks, at the same locations, at POST. I didn't notice those until now because they were well placed.
I have a DVI to HDMI cable which I started playing with: DVI connected instead of my 2nd monitor. The cable itself becomes HDMI, which I connected to my Dell monitor. Then I didn't have any blink during boot time (at POST). It was really smooth.
For some reason I can't output 1440p with this cable though. But I think this is a lead to the solution.
I can upload a comparison video if you'd like.

Anyway, I restored my ElCapitan to before the dsdt which disabled my USB ports, and booted without cache, and no blinks so far, but it's been running only for a couple of minutes so I can't be sure.
EDIT: Rebooted again with no cache and it started blinking again But we do have a lead, so that's something

Try just using HDMI to HDMI on the Dell monitor you have leave the second monitor disconnected and see what the outcome is. Ive used DVI to HDMI and never played very well with OS X. But in Windows it was a very different story.

 

[noambbv]

Try just using HDMI to HDMI on the Dell monitor you have leave the second monitor disconnected and see what the outcome is. Ive used DVI to HDMI and never played very well with OS X. But in Windows it was a very different story.

I used now HDMI to HDMI to boot without cache, from past experience it should blink (unless 'without cache' will make a difference. Ill put that to the test). it definitely blinked during POST, just like Dell's mDP to DP.
Here's a comparison between the blinks at POST, and the DVI to HDMI which has none: