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Background

Recently, I ordered an Alienware Aurora, Windows 7 Professional, with Double AMD Radeon™ HD 6950 CrossfireX™ at 2 GB each. So, it's got a total of 4 slots.

Along side with that order, I also bought 2 x Dell U2312HM DVI. The cables connected from the monitors to the computer are standard DVI.

What's happened

At first startup, both screens were lit and connected to each graphics card (1st slot and 3rd slot, assuming the 3rd slot is the 2nd graphics card). At first time boot, windows started initializing the desktop and adding the alienware theme. Both screens got a real cool alien background, but once it logged in (after it was done with the initialization), the second monitor (connected to the 3rd slot) stopped displaying anything at all. It was on, but the computer wasn't sending any information.

What I can take from this, is that the setup works, but something was changed at desktop initialization. I have since then, done a restart, and nothing changed. I can't figure out what's wrong, or how to fix the settings to display both monitors.

How to proceed?

Attempts

  • I have tested each screen separately in the 1st slot, both screens work just fine
  • I have tried to discover new monitors in both Windows Screen Resolution and in the Catalyst Control Center, but it keeps displaying "No other monitor has been identified/found"
  • I have triple-checked the input source on both monitors. Tested specifying DVI and just letting it be auto
  • I have tried using dvi-vga converters, but to no avail. I wasn't expecting it to work either, but I've run out of ideas here...
  • Update Connecting the 2nd monitor to the 2nd slot (1st graphics card) also works fine.

Update

After connecting the 2nd monitor to the 2nd slot (assuming it is the 1st graphics card), both screens are operational. I still don't know if they are being rendered on separate GPUs. When identifying GPUs in Catalyst Control Center, it says 1 on the first monitor and 2 respectively. Am I to assume they are using separate GPUs and are being rendered optimally?

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2 Answers 2

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When CrossFireX is enabled then the video ports above 2 will be turned off so that performance of the two cards can be combined and delivered on those primary and secondary ports (only).

From AMD/ATI:

Multiple Monitors with ATI CrossFireX™ Configuration

◦ When ATI CrossFireX™ is active other display devices other than the primary and secondary monitor connected to the Digital Video Interface (DVI) or Video Graphics Array (VGA) are rendered inactive.

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    I tried turning it off, and sure enough, 3rd and 4th slot were kickin'! I think I'll just use CrossFire and slots 1 and 2, so I'll get the most out of it though. That also explains why it turned off after first boot (probably turned it on). Thanks for the info!
    – ShadowScripter
    Commented Jan 10, 2012 at 3:19
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In your checklist you forgot to update or re-install the video driver and maybe even re-install Windows 7. Maybe Ati Tray Tools can help you to find the problem and check if crossfire is enabled. It's also good to read the manual.

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  • The video driver is up-to-date, I installed the one from the Drivers and Documentation cd. Re-installing windows seem a bit unnecessary. Crossfire is enabled. When I identify the GPUs (monitor 1 and 2 connected to slot 1 and 2), I get 1 and 2. Does that mean slot 1 and 2 on the first graphics card or graphics card 1 and 2, or GPU 1 and 2 out of 4? There's no comprehensive manual on this subject along with the documentation.
    – ShadowScripter
    Commented Jan 10, 2012 at 0:35
  • @ShadowScripter: I don't know but maybe ATT or GPU-Z can help.
    – Cybercartel
    Commented Jan 10, 2012 at 0:41
  • Updating the drivers is usually a good idea but in this case the problem is obvious. Crossfire (as well as SLI) will use both GPU to render, but only the outputs from the primary card.
    – Hennes
    Commented Aug 24, 2014 at 20:29

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