Dual monitors problem with GTX 970 DP/HMDI: both connector-types 00080000 (WORKAROUND)

[robbsen]

Hello,

I try to get my two screens to work. I use a MSI GTX 970 4G (2x DVI, 1x HDMI, 1x DP). My primary screen is a LG 34UC98-W connected via DP, as a secondary screen I want to use a LG 29UM65-W connected to HDMI.

I installed 10.13.6 using my LG34 and already connected to DP during the installation, CSM is disabled, I use 14.2 SMBios. After installing the web driver the monitor works fine. If I connect the LG29 and try to boot I got the "signal lost" issue, even if the monitor is turned off. It works if I hot swap the LG29 but of cause it would be nice to get it work properly. When hot swapping there is no new entry created in system report.

I another thread I found a possible solution in Clover but I didn't work. I entered the following in the graphics section:

- Dual link = 1
- VRAM = 4095
- Video ports = 4
- Boot display = tried values 0 to 4 which make no difference

I just finished this installation. Before that I installed OSX using the LG34 connected via HDMI port. When I switched the cables to DP I had the "signal lost" issue too and couldn't boot via DP at all (only booting in safe mode). Interestingly with the LG29 I could boot via HDMI, after reaching the desktop I regularly turned on the LG34 connected via DP and could set it as my main display in OSX system preferences/monitors. But then I got flashing glitches every few seconds and decided to try a new installation using DP from scratch. I also tried to change settings in graphics section in this scenario as described above but it could not fix the issues. In system report both monitors were listed but unfortunately LG29/HDMI as primary connection.

Hopefully someone know how to fix this.

Thanks

EDIT

I checked ioregistryexplorer. C@2 is the LG29, D@3 is the LG34 monitor. I have seen that the connector-type for C@2 is set to 00080000, which stands for HDMI. C@3 is also set to 00080000 but shouldn't it set to 00040000 which stands for Displayport (see pictures). Please can somebody confirm this?

 

[beep]

Are you using Whatevegreen?
https://github.com/acidanthera/WhateverGreen

Did you try with CMS enabled?

 

[robbsen]

Hello,

yes, WEG is included in Clover kext folder.

I also tried with CMS enabled using the previous installation but it only changed the resolution to the bad side.

 

[BreBo]

Hopefully someone know how to fix this.

Check if your card has the latest BIOS update.
For my Asus STRIX GTX 970 there was a BIOS update to Fix DP display issues with certain monitors.
I currently use triple monitors (2x DVI, 1x HDMI) without any issues.

 

[robbsen]

Check if your card has the latest BIOS update.
For my Asus STRIX GTX 970 there was a BIOS update to Fix DP display issues with certain monitors.
I currently use triple monitors (2x DVI, 1x HDMI) without any issues.

I will have a look. First search indicates there should be an update. Thanks

 

[robbsen]

Check if your card has the latest BIOS update.
For my Asus STRIX GTX 970 there was a BIOS update to Fix DP display issues with certain monitors.
I currently use triple monitors (2x DVI, 1x HDMI) without any issues.

I flashed the vbios to the latest one but the problem persists. Black screen when booting with both monitors enabled.

 

[beep]

Did you try another Smbios like 18.3?

 

[robbsen]

No, because I run Skylake. Why do you think this could work?

 

[robbsen]

After some more painful testing I gave up with this.

As a workaround I could manage to run the GTX along with the iGPU. OS X boots using the HD530 over HDMI to run the LG 29 monitor. Shortly before it reaches the login screen I get some graphic glitches (red and green boxes around the apple logo and distortions), then OS X switches to the LG34, connected to the GTX`s Displayport. When on desktop everything is running smooth. The connector type for the GTX is still 00080000 but anyway, for now I can live with that.