# Radeon HD 6870 with multiple monitors

## Proksima

Hi,

I'm trying to make 3 22'' monitors on my Radeon HD 6870 plugged into a 2.0 PCI-Express port. My system is amd64, I have an AMD-fx8150 processor and my system should support that setup just well. (Actually my final goal is to have 4 screens connected)

The problem is that, even though 2 screens work flawlessly, 3 screens just don't want to.

When trying to set it up in amdcccle, I get the following:

The current settings cannot be applied. Possible issues may include:

     -Display(s) cannot be enabled.

     -Setting(s) cannot be applied due to insufficient video memory.

I am using ati-drivers 12.2 with xorg.server-1.11.2-r2 and gentoo-sources-3.2.12.

When I brought this video card, they advertised 6 monitors, so I really think the problem comes from linux. Can anyone point me in the right direction to solve my problem.

Thank you all for your time,

Proksima

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## gorkypl

How are the monitors connected? With more than two monitors, at least one must be connected via DisplayPort - or, in another words, you can have a maximum of 2 non-DP monitors connected.

I am running three monitors on a HD5750 without problems, using open drivers (x11-drivers/xf86-video-ati) - if you do not need 3D acceleration open drivers are usually a better choice and I think 6870 is supported already.

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## Proksima

Yeah, after some more research, I learned I needed an ACTIVE Displayport to DVI adaptor. I was using passive ones so that's why it did not work.

I would like using the open-source drivers, but I'm starting to program using the GLSL shading language, so I just can't...

For those who have the same problem, the reason an active adaptor is needed instead of a passive one is that DVI and HDMI requires a clock, but my graphic cards (and most graphic cards) have only two.

Displayport does not need such clock so we use an active adaptor to convert the signal from Displayport to DVI.

In comparison, a passive adaptor just matches the pins between Displayport and DVI, thus the graphic card understand it is dealing with DVI monitor and still uses a clock for that monitor, even if it is plugged into a Displayport.

Hope this will help other people.

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