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Thread: Open source drivers force vsync for everything 3D - why?

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  1. #1

    Default Open source drivers force vsync for everything 3D - why?

    Why is vsync on for everything and can it be disabled for games?

    Using ubuntu 11.04

  2. #2
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    These are the two toggles, disable both for the best speed.

    vblank_mode (vsync)
    swapbufferswait (anti-tearing)

  3. #3

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    Where and how do I "toggle" them?

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    Quote Originally Posted by curaga View Post
    These are the two toggles, disable both for the best speed.

    vblank_mode (vsync)
    swapbufferswait (anti-tearing)
    Hmm, what happens if vblank_mode is disabled and swapbufferswait is enabled? And what's the difference between the two?

  5. #5
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    @Not so pretty now

    "man radeon", "man xorg.conf" for the latter, driconf for the former.

    @RealNC

    Last I tested that combo, it synced at twice the refresh rate (120fps cap). I don't know the internals, but I think that -wait is a lighter form that only avoids the blank, while vsync has a max cap of refresh rate.


    Me <3 editing

  6. #6

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    Quote Originally Posted by curaga View Post
    "man radeon", "man xorg.conf" for the latter, driconf for the former.
    Couldn't you just tell the commands? What is the point of me reading through xorg.conf man page if I only need one concrete thing. I see nothing that could be helpful:
    Code:
    man radeon | grep sync
                  XV_VSYNC is used to control whether textured adapter synchronizes the screen update to  the
                  XV_CRTC is used to control which display controller (crtc) the  textured  adapter  synchro‐
                  nizes  the screen update with when XV_VSYNC is enabled.  The default, 'auto'(-1), will sync
                  things  like clone mode where the user can best decide which display should be synced.  The
    man xorg.conf | grep sync
                  This option controls whether the log is flushed and/or synced to disk after  each  message.
                  Possible values are flush or sync.  Unset by default.
           HorizSync  horizsync-range
                  gives   the   range(s)   of   horizontal   sync   frequencies  supported  by  the  monitor.
                  horizsync-range may be a comma separated list of either discrete values or ranges  of  val‐
                  HTimings  hdisp hsyncstart hsyncend htotal
                  VTimings  vdisp vsyncstart vsyncend vtotal
                      of  the  VSync  signal.   "Composite" can be used to specify composite sync on hardware
                      used to select the composite sync polarity.
                  tal  timings.   These  numbers are the hdisp, hsyncstart, hsyncend, and htotal values.  The
                  the  vdisp,  vsyncstart, vsyncend, and vtotal values.  The final section is a list of flags
                  select  the  polarity of the VSync signal.  Composite can be used to specify composite sync
                  be used to select the composite sync polarity.  The HSkew and VScan options mentioned above
                  This option controls whether the video card should drive the sync signal on the green color


    You can set sync_vblank on a per-application basis.
    How?

  7. #7
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    Code:
    Option "SwapbuffersWait" "boolean"
    You can set sync_vblank on a per-application basis.
    Use driconf and look under performance tab.
    Last edited by DanL; 05-29-2011 at 12:14 PM.

  8. #8
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    Heh, that's a Linux user for you .
    With r300g I have to change both swapbufferswait and sync_vblank for vsync to be turned completely off. For swapbufferswait just add the option to your xorg.conf and set it to off. For sync_vblank use either driconf, although I then had to configure the .drirc file it creates in my home directory and change the "driver" entry to dri2 instead of the r300 it uses (but amusingly enough that doesn't seem to work with Narwhal ).

  9. #9
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    Quote Originally Posted by Not so pretty now View Post
    How?
    http://dri.freedesktop.org/wiki/Conf...Infrastructure

  10. #10
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    With swapbufferswait Off sync_vblank doesn't matter anymore and vsync is OFF.
    With swapbufferswait On and sync_vblank set to 0 vsync is OFF.
    With swapbufferswait On and sync_vblank set to 3 vsync is ON.
    You can set sync_vblank on a per-application basis.

    At least with Intel.

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