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Thread: State of multi-head with multiple radeon graphics cards?

  1. #1
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    Default State of multi-head with multiple radeon graphics cards?

    Hello,

    At work I've got a Radeon X1300 and I'm thinking of borrowing another to get three monitors attached to my computer.

    I saw that most >2 monitor setups are done with xinerama, which unfortunately means that 3d acceleration goes out the window.

    Since most posts about setups like these are a bit old, now that we've got PRIME and gpu offloading and DRI2 and whatnot, is there a better way to do triple head without loosing 3d? Obviously with a X1300 it's not for gaming, but I would like to still be able to run compiz and unity.

  2. #2
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    At the moment, your best bet for more than two displays is to get a radeon card that supports more than 2 displays (evergreen or newer). If you want to use multiple cards, you'll still have to use zaphod mode and xinerama. The xserver prime stuff paves the way for improved multi-card, but it's not implemented yet.

  3. #3
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    Quote Originally Posted by agd5f View Post
    At the moment, your best bet for more than two displays is to get a radeon card that supports more than 2 displays (evergreen or newer). If you want to use multiple cards, you'll still have to use zaphod mode and xinerama. The xserver prime stuff paves the way for improved multi-card, but it's not implemented yet.
    Thanks for the consise answer, and hopefully this will be improved in the future

  4. #4
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    Just to make sure you don't fall into that trap: If you have one card where you want to attach 3 or more monitors only 2 of them can be VGA, DVI or HDMI. Every additional monitor has to be a real DP monitor (native or active DP adapter).

  5. #5
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    Quote Originally Posted by droste View Post
    Just to make sure you don't fall into that trap: If you have one card where you want to attach 3 or more monitors only 2 of them can be VGA, DVI or HDMI. Every additional monitor has to be a real DP monitor (native or active DP adapter).
    The limitation is the number of display clocks (there are only 2 for non-DP monitors). As of kernel 3.7, you can actually have more than 2 non-DP monitors as long as they at least two of them have the exact same pixel clock. If you want more than two monitors with independent timings, you'll need to use DP monitors for that additional monitors.

  6. #6
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    What about cards like Sapphire Flex, which claim to support three normal (=non-DP) outputs? Are those supported?

    I have no idea what kind of hack they do to get that, if it's adding some real components or not.

  7. #7
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    I think they include a dp-to-DVI/HDMI converter on board, rather than having to have similar circuitry in an external dongle. Seems like a pretty slick idea in terms of convenience. IIRC the board I looked at supported 2 DVI plus 1 HDMI, and included an HDMI-to-DVI dongle to support a third DVI.

    If that's the case, then I think the drivers should support 3 displays just fine. If agd5f disagrees though, listen to him

  8. #8
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    Quote Originally Posted by bridgman View Post
    I think they include a dp-to-DVI/HDMI converter on board, rather than having to have similar circuitry in an external dongle. Seems like a pretty slick idea in terms of convenience. IIRC the board I looked at supported 2 DVI plus 1 HDMI, and included an HDMI-to-DVI dongle to support a third DVI.

    If that's the case, then I think the drivers should support 3 displays just fine. If agd5f disagrees though, listen to him
    OFF TOPIC: Hi bridgeman, good to see you around. I dont know if you can answer this, but here goes.... What is the state of AMD's linux commitment these days? It's been a long time since 2007 when AMD recommitted themselves to linux development. Is it still going as well in house?

  9. #9
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    Quote Originally Posted by bridgman View Post
    I think they include a dp-to-DVI/HDMI converter on board, rather than having to have similar circuitry in an external dongle. Seems like a pretty slick idea in terms of convenience. IIRC the board I looked at supported 2 DVI plus 1 HDMI, and included an HDMI-to-DVI dongle to support a third DVI.

    If that's the case, then I think the drivers should support 3 displays just fine. If agd5f disagrees though, listen to him
    Yes, that's exactly what they do and it should work fine with the open source driver. From the driver's perspective one of the DVI/HDMI ports looks like a DP port with an active DP to DVI convertor.

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