Dual Monitor on Dual Graphic Cards, doesn't detect 2nd monitor

Posted on 2012-08-26
Last Modified: 2012-08-28
I've a friend who got 2 Graphic Cards linked together (SLI), and for some reason Windows 7 doesn't detect his 2nd monitor.

Each graphic cards got 2 DVI, 1 HDMI, 1 DisplayPort.
There's a VGA port onboard but it's disabled.

Both monitor he got are quite old and got only VGA so he is using a VGA->DVI converter.

I've tried both monitor, alone, and they both work and their converter too.  

But the only port that is showing up in Windows is DVI PORT #1 ON VIDEO CARD #1.

Anyone can help with this problem?  Is there any setting in Catalyst that i should do to let Windows 7 detect both monitors?

I've tried all theses combinations, but none seems to allow Windows 7 to detect his 2nd monitor:
Mon1 on Card1.DVI1 + Mon2 on Card1.DVI2
Mon1 on Card1.DVI1 + Mon2 on Card2.DVI1
Mon1 on Card1.DVI1 + Mon2 on Card2.DVI2

Thanks for your help
Question by:cdebel
    LVL 15

    Expert Comment

    There seems to be some confusion here - you say that your friend's computer has two graphics card linked with SLI, which is nVidia, and then you refer to the use of Catalyst, which is Radeon (formerly ATI, now AMD). It can't be both, so which vendor's products are being used?
    LVL 70

    Accepted Solution

    Turn off SLI (or Crossfire, it these are Radeon cards).

    With SLI enabled the cards are linked to provide higher performance -- but only ONE of each of the different ports will then be active (i.e. one DVI, one HDMI, and one DisplayPort).

    To use two displays in SLI, you need to use two different port types - i.e. if you replace one of the monitors with one that uses HDMI it will work fine.   (A DVI monitor would work fine as well, as you could use a simple HDMI -> DVI adapter or cable).
    LVL 10

    Author Comment

    @Perarduaasomething: I don't know the correct term for that, but he got Catalyst on his computer, that's for sure.  I said SLI because i thought it was named like this.  Both cards are linked together by a thin cable between them.  The connector is on top of each card.  It's approx 1 inch long.

    @garycase: thanks a lot for those info.
    LVL 69

    Assisted Solution

    What are the cards that he has?  AMD uses Catalyst software for their Crossfire linked cards, while nVidia uses nView software for their SLI linked cards.  Crossfire allows two different Radeon model cards to be linked, while nVidia requires two of the same models.  You can't use Catalyst with nVidia cards, and vice versa.

    You can run two monitors in SLI mode:
    LVL 10

    Author Closing Comment

    I've just tested it (deactivated CrossFireX) and it successfuly detected the 2nd monitor.

    I've advised him about that little particularity of having 1 monitor per port type if he want to reactivate it.

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