From: Axel Kohlmeyer (
Date: Wed Aug 31 2011 - 10:17:39 CDT

dear pawel,

2011/8/31 Paweł Kędzierski <>:
> Dear VMD users,
> I have recently bought a laptop with Nvidia card GT540M in order to make use
> of CUDA software. This is a DELL XPS 502 with i7 SandyBridge, which means
> "Optimus technology". The system is Windows 7 64bit Home Premium.
> VMD 1.9 reports this:
> Info) Multithreading available, 8 CPUs detected.
> Info) Free system memory: 4095MB (100%)
> Info) Creating CUDA device pool and initializing hardware...
> Info) Detected 1 available CUDA accelerator:
> Info)   [0] GeForce GT 540M     2 SM_2.1 @ 1.34 GHz, 2014MB RAM, KTO, OIO,
> Info) OpenGL renderer: GeForce GT 540M/PCI/SSE2
> Info)   Full GLSL rendering mode is available.
> Info)   Textures: 2-D (16384x16384), 3-D (2048x2048x2048), Multitexture (4)
> The driver is the original one which came with the system. As reported by
> GPU-Z (dxdiag never shows nvidia info, only intel IGP, whatever I try) it
> is:
> nvlddmkm (ForceWare 265.94)
> Now the questions:
> the line with [0] reports "2 SM_2.1 @ 1.34 GHz" - does it mean, that it uses
> only 2 out of 96 shaders (!!)?

no. it means 2 multiprocessors, i don't know this GPU,
but each multi processor probably has 48 cores.

> if yes, what can I do to make use of more "cores" of this card for CUDA?
> is it possible - with two graphic cards at hand - to make VMD use the Intel
> IGP for display and NVidia for CUDA calculations?

fi you configure your display to only use the intel chip
for (OpenGL) graphics, then that is what VMD will use.

> Actually right now VMD seem to be the only program which is able to run this
> Nvidia chip on this system. Settings in both Win7 and NVIDIA Control Panel
> does not seem to affect other programs. Even if I max out the performance
> settings and set the system to use the GPU for everything, it does not seem
> to work.
> Therefore I am not even sure if VMD does use the GPU or only pretends to.
> For example, I am getting about 30-34FPS in fullscreen (FullHD) when
> rotating a 1RBX pdb structure in Licorice with Sphere and Bond resolutions
> bumped up to 25. Does this kind of performance sound about correct or does
> it rather indicate I am running on the integrated graphics?

you have to separate CUDA and OpenGL.
both are two separate APIs and VMD will use both.
CUDA for certain computing tasks and OpenGL
for graphics. the nvidia driver will do the "multiplexing".

the OpenGL renderer line says that VMD uses
the nvidia GPU for graphics. unless your driver
does something crazy and "lies" about who and
what it is, that is what i would assume is being used.


> Thanks in advance,
> Pawel Kedzierski

Dr. Axel Kohlmeyer
Institute for Computational Molecular Science
Temple University, Philadelphia PA, USA.