PCIE video cards and DRI

[Gain Paolo Mureddu]

Jack Howarth wrote:

>    Does anyone know if DRI is fully enabled under the latest
>Nvidia and ATI closed source drivers when used with PCI-Express
>cards. I have set up a number of Linux boxes with Nvidia and ATI
>AGP cards and DRI has always accelerated nicely. However I can
>find little information on the web concerning how well DRI and
>PCIE play together. In particular, are there any limitations to
>DRI support of PCI-E currently that would severely degrade the
>performance of opengl. For example, the ATI fglrx drivers on
>a Radeon 9600-XT improve in glxgears frame rate from 200 to 2000 fps
>upon loading the fglrx kernel module. Will a similiar performance
>improvements be possible with DRI on PCI-E cards? Thanks in 
>advance for any advice since I don't want to get stuck with
>horrible graphics performance under Linux just because DRI is
>AGP-centric.
>             Jack
>
>  
>
That would depend on what do you mean by DRI. If you mean only the 
Direct Rendering Infrastructure approac of rendering 3D graphics, the 
answer is yes. Both closed source drivers from ATi and nVidia recently 
support their PCI-E products for Linux. If by DRI you mean the DRI 
project, then I could not say... I don't know if there's any board 
supported by the project in PCI-E "format" out on the market yet.

As for performance... As of yet, the improvement of PCI-E over AGP 8X is 
not very noticeable (it is arguable how much of an improvement in 
performance if percieved), general concensus say that it is not big an 
improvement over 8X AGP with the currently available products. However 
as PCI-E products hit the market and popularize, it is most likely that 
16X and higher boards will be seen and then the difference should be 
enormous. For the time being though, PCI-E is more a testing ground and 
a glimpse of what the future interface for grphics and high bandwidth 
PCI applications will be.

I don't have much experience with PCI-E due to the lack of availability 
down here in Mexico, though in Linux for the time being, and as ATi 
irons down their drivers, I think your best bet would be to get an 
nVidia card. Right now from self experience I can tell you that ATi 
drivers are getting there, though they're not quite there yet (I'd 
estimate a year or so before we see the amount of performance equivalent 
products from nVidia offer in Linux from ATi solutions). The main focus 
has never been speed, but compatibility, stability and precision (again 
from self experience I can atest to the higher image quality of the 
Radeon cards on Linux with the fglrx drivers, though nVidia drivers are 
much faster). So in the end, the decision is yours alone.

Good luck.