Bug#532926: xserver-xorg-video-ati: XRandR multi-monitor: slowness on one screen, acceleration on the other

Alex Deucher alexdeucher at gmail.com
Mon Jun 15 17:03:44 PDT 2009

On Sun, Jun 14, 2009 at 9:07 PM, Arno Schuring<aelschuring at hotmail.com> wrote:
> Alex Deucher wrote:
>> Rotation uses the 3D engine so the largest desktop size that can be
>> rotated with hardware is limited to the max texture size: 2048x2048
>> for your card.  For desktops larger than that, software is used for
>> rotation.  1280 + 1920 > 2048.
> Ah, I see. That does explain the speed difference between the monitors.
> I take it that xv does not use the 3D engine then.

Xv uses the 3D engine for the textured video adapter.  The overlay
adapter does not. The max texture size is 2k, while the max render
target size is closer to 4k, so Xv isn't a problem as long as the Xv
source data is > 2k.

> I'll have to go hunting for a new (AGP) videocard, then. And fall back
> to using one monitor in the meantime.
>> Due current architectural limitations,
>> the max size is per-desktop rather than per monitor.
> Since I'm thinking about testing the whole kms-thing anyway as soon as
> it's in the mainline kernel, is there any chance that the radeon-rewrite
> driver does not have this limit?

The solution will be implemented xserver and driver side via EXA
changes.  This is being addressed in the shatter work being done right
now as a GSOC project.


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