3D MergedFB radeon support for screens > 2048x2048 ?

[Alex Deucher]

On 9/13/06, Mitch <Mitch at hasbox.com> wrote:
> Thanks Alex that does answer it. Yes i think the manpage does need
> updating especially the bit that says
>
>         The maximum framebuffer size that the 2D acceleration engine can
>         handle  is  8192x8192.  The maximum framebuffer size that the 3D
>         engine can handle is 2048x2048.
>
> this is why i was assuming that 3D was disabled on my radeon 9200pro
> with mergedfb at 2560x1024.
>
> I was also hoping it would explain the ridiculous performance i'm seeing
> with the xorg radeon driver. Xgl or even xcompmgr is out of the
> question. I have found another thread saying that EXA is essentially
> broken with radeon (rv280) driver. I'm still digging.. I will be trying
> the proprietrary ati driver next to see if it's any better.

EXA Composite acceleration won't work if your desktop is larger than
2048 in either direction since it uses the 3D engine.

Alex

>
> M
>
> -------- Original Message --------
> Subject: Re: 3D MergedFB radeon support for screens > 2048x2048 ?
> Date: Wed, 13 Sep 2006 09:42:24 -0400
> From: Alex Deucher <alexdeucher at gmail.com>
> To: Mitch <Mitch at hasbox.com>
> CC: xorg at lists.freedesktop.org
> References: <4507B052.6020501 at HasBox.COM>
>
> On 9/13/06, Mitch <Mitch at hasbox.com> wrote:
> > Hi,
> >
> > Screen resolutions of 1280x1024 are pretty much standard these days and
> > i note from the radeon man page that 3D is disabled for Mergedfb when
> > using two screens with a combined resolution of more than 2048x2048.
>
> the coordinate limits (and tiled surface surface limits) are 2048 on
> r100 and r200 based radeons.  It's 4096x4096 theoretically on r300 and
> above. Also, 3D isn't disabled, it just does not work on surfaces
> wider or tall than 2048 pixels from the start of the visual
> framebuffer.  I suppose the man page should be updated to refect the
> limits of r100/r200 vis r300 and above.
>
> >
> > So what's the solution if you want to use dual screens (bringing the
> > resolution upto 2560x2048) with 3D support ? I'm assuming there is a
> > technical reason why it's not supported at this res ? Is the limitation
> > not there in the propiterary ATI drivers (before i start downloading 56M
> > of driver) ? What about using Xinerama ? Any other ideas apart from
> > forcing my resolution to 1024x1024 for each screen ?
>
> AFAIK, the ATI driver has the same limitations.  Those are hardware
> limits.  If you have an r300 chip or above you should be ok.
> Theoretically, if you had a single 3D context that was larger than
> 2048 in either dimension, you could split it up into tiles and iterate
> across them, but it's a lot of work and no one has stepped up to do
> it.  Another alternative would be if you didn't need any 3D conects to
> be wider/taller than 2048, but you wanted working 3D at offsets
> greater than 2048 pixels into the framebuffer would be to update the
> 3d engine's base address to match the start of the 3D surface rather
> than setting it to the framebuffer base as it is now.
>
> I hope that helps,
>
> Alex
>
> >
> > Thanks
> > M
> > _______________________________________________
> > xorg mailing list
> > xorg at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/xorg
> >
> _______________________________________________
> xorg mailing list
> xorg at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/xorg
> _______________________________________________
> xorg mailing list
> xorg at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/xorg
>