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Thread: 4850 driver - ati vs radeonhd

  1. #1
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    Default 4850 driver - ati vs radeonhd

    Hi all, anyone had experience with the 4850 card and recent versions of the open source drivers? I'd just like to know which way to go.

    Also, I'll be installing Kubuntu 8.10 - is changing drivers as simple as editing xorg.conf and restarting X?

    Thanks for any tips!

  2. #2
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    I got an 4870. At first I tried the radeonhd driver. But it seems the card gets too hot. The fan is spinning up and down all the time. Then I tried the radeon driver. The noise stopped.

    Both drivers don't seem to support 3D/direct rendering. The radeon drivers seems a bit faster.

    I wonder what the radeonhd driver is good for. It's a total fail right now.

  3. #3
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    Could you try running radeonhd but using atombios for initialization and modesetting, to see if that changes the fan behaviour ? I think you enable it by adding the following to the Device section :

    Option "UseAtomBIOS" "True"
    Last edited by bridgman; 09-08-2008 at 06:46 PM.

  4. #4
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    Mesa (the open source 3d stack) doesn't support 3d acceleration for your card at present, but support should (hopefully) be coming soon.

    The radeonhd and radeon drivers are actually fairly similar, but differ in how they do modesetting. Radeonhd does modesetting using the card's native registers (when possible, it also has support for atombios), which has the advantage of being fast and "open," but the disadvantage of being harder to program. Radeon uses atombios exclusively, which makes the driver easier to write, but depends on the (sometimes buggy) atombios interpreter of the card to function, which is also a bit slower (for modesetting.)
    Last edited by TechMage89; 09-08-2008 at 09:21 PM.

  5. #5
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    Thanks for all the info guys.

    So what about video? I know that fglrx currently has issues with Xv scaling/tearing. Are the open source drivers better in this regard? Is one better than the other?

  6. #6
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    No, Xv is tearing no matter which driver you use. The only way to have tearless video is to use Gl instead of Xv and enable vsync, and this requires fglrx since neither radeon nor radeonhd support direct rendering on the 4xxx cards.

    @bridgman:
    On the 4xxx cards, radeonhd defaults to AtomBIOS (as seem in X's startup log).

  7. #7
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    At present, if you want any kind of acceleration, your only choice is fglrx.

    Acceleration with the open-source drivers should be arriving in a few months.

    Xv tearing for cards with textured video (on the open source driver) *can* be fixed with the patch found here: http://www.botchco.com/agd5f/?p=30

    Note that this patch works by stalling rendering until the scanning line is passed, meaning it's sort of a hack and might cause jittery video performance for lower-end cards. The ideal way to vsync is to double-buffer, but that's a lot harder to implement.

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