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Old 07-26-11, 01:48 PM   #1
Wadlax
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Default OpenGL performance - 2 cards Geforce GTX 470 , 4 Monitors, slow xinerama

Hello.

MB ASUS M4N98TD EVO ( NVIDIA nForce 980a SLI )
AMD Phenom(tm) II X6 1090T Processor
2 x Geforce GTX 470 (not SLI-connected) from MSI
4 x 1920x1080 monitors
16 gb ram
Nvidia drivers 275.19
Xorg server 1.10.2
Gentoo Linux x86_64 , KDE ,


OpenGL performance with some xorg setups

Code:
xorg.conf set with nvidia-settings

full xinerama -- 4 screens with xinerama
xinerama twinview -- xinerama connects 2 screens with twinview on 2 monitors
no xinerama twinview -- 2 separate screens with twinview on 2 monitors
no xinerama 38-42 fps -- 4 separate screens


Code:
  EVE-Online
  (wine-1.3.24 , i used same ingame scenes to benchmark)
full xinerama      __ 13-14 fps
xinerama, twinview    __ 27-30 fps
no xinerama, twinview __ 38-42 fps
no xinerama    __ 38-42 fps


  MegaGlassCube
  ( GLScene benchmark - rotates 5000 semi transparent cubes )
full xinerama     __ 20-22 fps
xinerama, twinview    __  27-28 fps
no xinerama, twinview  __ 32-33 fps
no xinerama     __ 31-32 fps


  GLXgears
  (small window, not resized = high fps)
full xinerama     __ 15400 fps
xinerama, twinview   __  17000 fps
no xinerama, twinview   __  18400 fps
no xinerama    __ 18400 fps

Questions :

Main - 1. Did i missed some hand-made settings? I used nvidia-settings to setup my xorg.conf file.
( maybe --enable-fast-xinerama )
Is there any chance to get full performance and Xinerama?


2. nvidia-settings: If i change "Digital Vibrance" on all monitors -- after reboot it is set to zero on monitors 1-3. Monitor 0 value is remembered.


nvidia-bug-report.log.gz -- sent to _linux-bugs at nvidia_com_ with link to current thread

Last edited by Wadlax; 07-26-11 at 01:53 PM. Reason: nvidia-bug-report.log
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Old 07-27-11, 07:09 AM   #2
JaXXoN
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Join Date: Jul 2005
Location: Munich
Posts: 910
Default Re: OpenGL performance - 2 cards Geforce GTX 470 , 4 Monitors, slow xinerama

Xinerama splits up the OpenGL command stream for the two
cards. That causes quite some friction.

With one card + two video splitters you get about 30% more
performance (compared to two cards + xinerama at the same
resolution). In case you have DVI, you would need two
TripleHead2Go boxes (DualHead2Go DVI is not recommendable
because it has a VGA input, only). If you have DP, then DH2Gs
would be sufficient in your case.

Unfortunately, those Matrox video splitters are not exactly cheap.
However, after running into tons of issues with mutli-GPU setups,
I decided to purchase those devices a couple of years ago and
they easily payed off because its much simple to handle a single
GPU (most importantly driver wise, but also having less issues
with casing, cooling and PSU, etc).

regards

Bernhard
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