Have to Unplug Monitor During Boot or Graphics Card Won't Work

[rocco_77]

Finally got El Capitan working... no sleep wake, but I just keep my comp running, so I live with that.

I have one issue with graphics card however that is strange.

When I turn on my computer or restart, I have to unplug my monitor(s) until the boot reaches the clover screen or the sign in screen. (I guess at when to plug my monitors back in)

If I do this, all is well. If I leave monitors plugged in, it boots, but I get a flashing square on my monitor of white and the top corner of the sign in screen in the top left quadrant of the monitor. ??

It seems during post to clover screen, my graphics card isn't initializing properly or something, I don't know.

Can anyone help?

My build is below, and I'm using 2 20" Apple Cinema Displays for monitors.
Main monitor in one of the DVI ports and one in a Lightning Port.

By the way, it doesn't matter if I use one monitor or have both plugged in at boot up or restart, same issue.

Mobo: GIGABYTE GA-Z68MX-UD2H-B3
CPU: Intel Core i7-2600K
GPU: GIGABYTE ATI Radeon HD6870 1GB DDR5 2DVI/HDMI/2x
RAM: Corsair Vengeance Blue 16 GB DDR3 SDRAM Dual Channel Memory Kit CMZ16GX3M4A1600?C9B
HD0 (for OS and Apps): OCZ Technology 120 GB Vertex Series SATA II Solid State Drive
HD1 (file storage, Adobe scratch disk): Samsung 1 TB Spinpoint 7200 RPM 32MB Cache SATA
BURNER: LG CD/DVD Burner Model GH22NS50
CPU COOLER: Corsair Cooling Hydro Series H50 All in One High-performance CPU Cooler CWCH50-1
P/S: Antec CP-850 850 Watt CPX Power Supply Unit
CASE: Antec Performance One P183 V3 Case

 

[rocco_77]

I found a workaround either here or on another forum.

In BIOS... Legacy F10 is mine. I set the Init Display First to Onboard.

Since I don't have a monitor plugged into the onboard port, I don't see anything from post until the El Capitan sign in screen.

This allows me to boot without unplugging and replugging monitors during boot.

The only caveat is now in my Settings > Display I have a smaller third monitor. I have dual 20" cinema displays running off the graphics card.

There has to be a way to not have to have this workaround... right?
Can anybody be offer another solution? Thanks!

 

[baryw]

Having a similar problem with a HD 6850. I am going to try some of your tricks and see if I can figure anything out.

 

[baryw]

I changed my BIOS to Onboard and now I don't see the flashing square. I do have a black screen though.

Something different...

I am going to keep testing...

 

[baryw]

Hi - I have found this issue to be related to the display I was using. I was using an older Apple Cinema display. Once I switched to a newer ViewSonic, the problem went away and things worked normally.

Try to find a different monitor if you are having this problem.