From: Paweł Kędzierski (
Date: Wed Aug 31 2011 - 09:02:09 CDT

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 CUDA?
  * 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