Weird triple-screen issue 2560x1440 + 2x 1920x1200

[KingFatty]

Three monitors, 2560x1440, 1920x1200, and 1920x1200.

When I connect my 2560x1440 monitor using the video card's displayport, I can run an extended desktop of three monitors (the 1920x1200 monitors connected either by DVI, HDMI, or displayport).

But when I connect the 2560x1440 monitor using the video card's only dual-link DVI (beefy cable that came with the display), I can only connect one more display, regardless whether I use displayport or HDMI. I even tried putting both of the 1920x1200 displays on the mini displayports, but still no triple support extended desktop.

The video card has one dual-link DVI, one HDMI, and two mini displayports.
The 1920x1200 displays, if connected via displayport, are using an active single-link converter to convert the video card output to DVI.

I've never encountered this before I got the 2560x1440 display - triple screen would work regardless of which connection was used. But for now it seems I cannot enable triple screen display if the 2560x1440 uses the DVI connector. When I try to, Windows provides a message along the lines of "cannot enable additional screen," and AMD control panel says "To enable that screen, you must disable an existing screen."

I'm not sure if this is a driver issue or a hardware limitation of the video card, so can anyone test this out?

Specifically, I'm running crossfire 7950 video cards (Powerecolor PCS+). The same issue happens on either card, whether crossfire is enabled or disabled.

And this happens in windows. Regardless of whether I use Windows native resolution properties on the desktop, or the AMD control panel. It's got me stumped, but I'll try the new AMD beta drivers tonight.

 

[Plimogz]

I use 3 monitors (1 2560x1440 & 2 1920x1080) with the 2560x1440 connected by DVI and the others running off mini-displayports (the screens have native displayport, unlike yours, however). And everything is plugged into one 7950. This is running Win7.

Extended desktop works fine for me in this configuration.

 

[BonzaiDuck]

Somebody enlighten me.

I had for a time used Lucid-Virtu which had come with my mobo -- teaming my iGPU with the dGPU. But it was in dGPU mode. I was running two monitors (HDTV and desktop) off the dGPU. In process of troubleshooting something else, and given the lackluster assessments of Lucid, I uninstalled the Lucid package and did what I could to disable the iGPU.

During this exploration, I investigated SLI configurations -- discovering for one thing that you can't integrate iGPU and SLI. I came across some pages at the NVidia web-site pertaining to SLI.

I can't remember if one was able to connect monitor(s) to both SLI enabled graphics cards.

So I'm wondering if this might offer an option or solution avenue to the OP's Crossfire configuration.

I can connect up to three monitors to my GTX 780 card, but earlier and less powerful cards only allowed for two monitors before running into trouble.

Does anyone remember the possible monitor connection options with SLI or Crossfire-enabled multi-GPU setups?

 

[KingFatty]

I'm going to try physically pulling out one of the video cards to see if the issue is resolved.

I also will try out a 1600x1200 display as the 3rd screen, instead of the 1920x1200, to see if the lower total pixel count might resolve the issue.