From: Axel Kohlmeyer (akohlmey_at_gmail.com)
Date: Thu Jan 27 2011 - 08:17:19 CST

On Thu, 2011-01-27 at 14:24 +0100, Ramon Crehuet wrote:
> Dear vmd experts!

dear ramon,

> I am running VMD 1.8.7 in two dell Workstations Precision T1500. Both run Ubunto
> 10.04. (Maybe some of the installed or updates packages are different) The
> graphics card, detected by VMD is:
>
> Info) Detected 1 available CUDA accelerator:
> Info) [0] Quadro FX 580 4 SM_1.1 @ 1.12 GHz, 511MB RAM, KTO, OIO
> Info) Creating CUDA device pool and initializing hardware...
> Warning) Detected X11 'Composite' extension: if incorrect display occurs
> Warning) try disabling this optional X server feature.
> Info) OpenGL renderer: Quadro FX 580/PCI/SSE2
> Info) Features: STENCIL MSAA(16) MDE CVA MTX NPOT PP PS GLSL(OVF)
> Info) Full GLSL rendering mode is available.
> Info) Textures: 2-D (8192x8192), 3-D (2048x2048x2048), Multitexture (4)

do you get the _identical_ output for both machines??

> One of the workstations has 1 monitor, the other has 2 monitors. Displaying the
> same proteins, in the frist case I get around 100 FPS and in the second 10 FPS.
> Is that normal?

the FPS rate depends on many things, e.g. the dimensions of the
VMD OpenGL window, what other applications are running at the same
time, and whether they use OpenGL as well or not. dual screen operation
certainly does impact the FPS rate. but so does resolution and
colordepth, antialiasing and many other details.

> Is there a way to change the settings of NVIDIA driver to increase performance?

first of all you should try and see, if both machines have been
configured the same way and give the same performance under
identical settings.

then you have to check how the multi-screen display is configured.
there are two options for nvidia gpus, xinerama and TwinView.

finally, your GPU is not exactly a high-end GPU (to say the least),
it is very unlikely, but possible that the dual screen setup is
just overloading it beyond its capability.

in short, there is no way to recommend some "magic setting"
that will make the GPU perform lightning fast. first you have
to understand what feature/flag/setting it is that is responsible
for the difference.

cheers,
    axel.

> Thanks in advance,
>
> Ramon
>

-- 
Dr. Axel Kohlmeyer
akohlmey_at_gmail.com http://goo.gl/1wk0
Institute for Computational Molecular Science
Temple University, Philadelphia PA, USA.