I have three monitors connected, but one remains black.

[nothintoulouse]

Alright I have a radeon HD6900, which comes with one HDMI, two mini display, one DVI-I and one DVI-D port. I wanted to connect 3 Displays to it.
I can't connect any screens to the motherboard, because they wont get detected.

Now I have one display in the HDMI port and one in the DVI-I port and they work fine and I can arrange them the way I want.

But as soon as I plug the third monitor into the mini display port (the only port I have left), suddenly, only the screen in the HDMI port works and the others don't.
They get detected and I can still move my mouse into them, but they stay black and in windows, the third monitor shows up smaller than the other two, and I can't move that one around.

Thanks for help in advance!

 

[Armageus]

What monitors do you have / what connections have they got?

You may be able to get away with 2 connected via DVI, and the other connected via HDMI, as long as at least 2 of the monitors are identical.

Also what motherboard/processor do you have? As on most intel boards/chips, you can still use the motherboard outputs in addition to your graphics card.

 

[nothintoulouse]

What monitors do you have / what connections have they got?

You may be able to get away with 2 connected via DVI, and the other connected via HDMI, as long as at least 2 of the monitors are identical.

Also what motherboard/processor do you have? As on most intel boards/chips, you can still use the motherboard outputs in addition to your graphics card.

It is complicated: The one connected via HDMI is a large TV and I have two identical BenQ GW2270 monitors, one on either side of the TV.

I have an AMD processor and usually, you have to go into the BIOS and activate 'surroundview' ,which allows you to have displays connected to the GPU and the motherboard, but somehow, activating this hasn't changed a thing. I have got two HDMI cables and one VGA cable. The vga cable is plugged into the DVI via an adapter, and the HDMI cable for the third monitor has an hdmi to mini display port adapter.

So: One TV, two identical monitors; all connected to different ports.
TV in HDMI
Monitor in DVI-I via VGA cable with adapter
monitor in Mini display port via HDMI cable with adpter.

 

[Armageus]

So: One TV, two identical monitors; all connected to different ports.
TV in HDMI
Monitor in DVI-I via VGA cable with adapter
monitor in Mini display port via HDMI cable with adpter.

By running them in this way, I think what is happening is the card only has two physical clock generators (used by DVI/HDMI/VGA/and passive display port adapters, but NOT for native display port), when you need 3 due to how they are connected.

In theory if you changed them as follows you should be ok (can't say for definite, as only really see it mention on the newer 200 series cards).

TV - leave in HDMI
Monitor 1 - DVI cable
Monitor 2 - DVI cable

In theory, this should allow the card to detect both monitors are the same (and run at same res/refresh rate), and share one of the clock generators.



If that doesn't work, then you will need an Active (mini) displayport to DVI or adapter to connect at least one of the monitors.