ATI dropping support for <R600 - wtf!?

[bridgman]

So, glxgears actually doesn't fully utilize GPU?

Right. The glxgears program uses only fixed-function graphics (no shaders), and draws shaded triangles with no textures. Between shaders and textures that's maybe between 80% of a modern GPU sitting idle. Vertex shaders get used to emulate the fixed-function transform and lighting, but that's about it. The only block that works hard is the ROP/RBE, ie the part that handles depth compare (Z-buffer) and writes pixels into video memory.

Even worse, since older chips used relatively more of their silicon area for ROP/RBE than new chips, it's not unusual for an old GPU to outperform a new GPU on glxgears.

OK, now I understand: latest open source drivers are actually in good shape regarding performance, but those latest bits of code still aren't included in most of distributions (what users actually see). So, could we see good open source 3D performance and power management by the end of this year (I mean in Ubuntu 9.10/Fedora 12)?

I think so. The end-of-year distros are probably the first ones which will be able to ship with all this new stuff, but it should be available for download & build sooner.

Power management is the only part that hasn't really been implemented yet (everything else has been implemented but not integrated), but for 5xx and below I *think* it should come together fairly quickly once the invasive drm changes start to settle down.

[RealNC]

DX10 cards even have those "unified shaders" anyway, where the distinction between geometry, vertex and pixel processors becomes fuzzy. I think glxgears doesn't have any access to this feature, so it uses the small (fixed) percentage of shaders that are assigned to it by the driver. I think ATI cards give about 30% of their processors to vertex/geomerty. The other 70% is dedicated to pixel shading and is not accessible to glxgears at all. So in other words, glxgears only uses 30% of a modern GPU.

I think this 30%/70% ratio started with the X1900.

(I hope I got the above right :P)

[Mr_Ed]

Right now the current fglrx driver gives me much better performance (2d and 3d) on my 9600 XT/TV (rv350) card then the open source driver does.

But from reading this thread I understand that fglrx will not support my 9600 card anymore and I am forced to switch to the open source driver?

Is that correct?

[RealNC]

Yes. Though I preferred the open driver on my X1950XT anyway. Catalyst was faster, but bugged like hell. With the open driver, everything was working correctly, even though 3D was slower.

[BlackStar]

(I hope I got the above right :P)

You are not far off the mark. The unified architecture was introduced with R600 (the 2000 series). R500 is still old-style vertex & fragment shaders, which is why it can be accelerated using the same code as R300/R400.

Other than that, unified shaders means that the drivers and/or hardware can dynamically balance resources according to the utilization. In other words, if your program is 90% vertex shader and 10% fragment shader computation, a unified architecture will be able to allocate the hardware resources to match that. An old-style architecture, like R500, would leave the fragment processing hardware underutilized, in this 90/10 scenario.

But from reading this thread I understand that fglrx will not support my 9600 card anymore and I am forced to switch to the open source driver?

Is that correct?

Yes. You'll be able to use fglrx with the 2.6.28 kernel and XServer 1.5 (and maybe 1.6), but you'll have to change to radeon/radeonhd once new versions arrive.

[bridgman]

Right now the current fglrx driver gives me much better performance (2d and 3d) on my 9600 XT/TV (rv350) card then the open source driver does.

I agree that 3d performance is better on fglrx than on the open source drivers, but most users seem to be reporting better 2d performance with the open source drivers.

Are you using XAA or EXA acceleration with the open source drivers ? I think the default is still XAA, but EXA often gives better performance these days.

[Mr_Ed]

Conclusion: I will not ever going to be able to use the fancy stuff like desktop effects (compiz, AWN, screenlets, blurred window borders, etc.) since this is slow like hell when using the open source driver. Google earth doesn't even work with it.

While I have been waiting for a few years for the fglrx driver to solve all this for me, I feel pretty much screwed now by ATI.

Bummer!

[Mr_Ed]

Yeah, I tried the open source driver with EXA, it doesnt work well.

[Saist]

Conclusion: I will not ever going to be able to use the fancy stuff like desktop effects (compiz, AWN, screenlets, blurred window borders, etc.) since this is slow like hell when using the open source driver. Google earth doesn't even work with it.

interesting... I was able to use Beryl on a Radeon 8500 using the X.org ATi driver off of Mepis 6.5 with no problem, and I seriously doubt you can get much slower than that when it comes to 3d rendering on the open source X.org ATi driver.

[bridgman]

Yeah, something is wrong here, maybe drm not initializing properly (it won't start up unless you fully uninstall fglrx and reboot before starting with the open driver. That would explain both 2d and 3d running slow (but it's only a guess).