From: John Stone (
Date: Wed Aug 31 2011 - 10:19:39 CDT

  The "SM" count reported by VMD is the number of
"streaming multiprocessors" on the device. Each SM contains multiple
smaller processing units, which on the graphics side are called "shaders".
This is why you see 2 listed rather than 96. VMD will automatically use
the GPU for calculation of electrostatics, display of molecular orbitals,
calculation of radial distribution functions, and a few other things.
The next version of VMD will use the GPU to accelerate much more.
If you're curious how fast your GPU runs, you can run this command:
  vmdbench cudamadd 0

Regarding VMD's use of the GPUs:
  VMD will always use CUDA whenever it can, irrespective of the
display settings on the Intel IGP.

On the graphics side, it does sound to me like you're using the
NVIDIA GPU and not the Intel GPU based on the performance numbers
you gave. Also, you can see that VMD identifies the attached OpenGL
context as being connected to the NVIDIA GPU, and not the Intel IGP:
   Info) OpenGL renderer: GeForce GT 540M/PCI/SSE2

Let us know if you have more questions.

  John Stone

On Wed, Aug 31, 2011 at 04:02:09PM +0200, Pawe? K?dzierski wrote:
> 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, ZCP
> 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 (!!)?
> * if yes, what can I do to make use of more "cores" of this card for
> * is it possible - with two graphic cards at hand - to make VMD use the
> Intel IGP for display and NVidia for CUDA calculations?
> 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?
> Thanks in advance,
> Pawel Kedzierski

NIH Resource for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801           Phone: 217-244-3349       Fax: 217-244-6078