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Old 07-22-10, 06:31 AM   #1
Ulukai
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Join Date: Jul 2010
Posts: 45
Default Geforce GTX SLI under Linux

I'm thinking of getting a pair of GTX 470's to SLI under Linux, so I was reading some information and found this in the readme of the latest Linux driver. As it says, it would be only temporary, but I coudln't help noticing it's in the readme a very long time already: driver 180+ and even older.

Why is Doom 3 slower when SLI or Multi-GPU is enabled?


The NVIDIA Accelerated Linux Graphics Driver does not automatically detect the optimal SLI or Multi-GPU settings for games such as Doom 3 and Quake 4. To work around this issue, the environment variable __GL_DOOM3 can be set to tell OpenGL that Doom 3's optimal settings should be used. In Bash, this can be done in the same command that launches Doom 3 so the environment variable does not remain set for other OpenGL applications started in the same session:

% __GL_DOOM3=1 doom3

Doom 3's startup script can also be modified to set this environment variable:

#!/bin/sh
# Needed to make symlinks/shortcuts work.
# the binaries must run with correct working directory
cd "/usr/local/games/doom3/"
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:.
export __GL_DOOM3=1
exec ./doom.x86 "$@"

This environment variable is temporary and will be removed in the future.


So a couple of questions about this:

- Does it really still apply or did someone forget to remove it from the readme?
- To fix this for Quake 4 (and maybe Prey too?), do we have to use the same variable with the same name (__GL_DOOM3) or is it called different?
- When I enable SLI in xorg.conf, should I have 2 sections "device" for both cards?

Thanks for your help,

Ulukai.

Last edited by Ulukai; 07-26-10 at 03:06 AM.
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