Re: Three GPU cards on shared-mem motherboard

From: Aron Broom (
Date: Wed May 30 2012 - 09:14:17 CDT

I haven't seen GTX600 series benchmarks for NAMD, those would be very
nice. These new consumer 600 series cards have substantially less double
precision computational power than the 500 series, but a lot more single
precision. From my understanding, NAMD and OpenMM/GROMACS do all single
precision on the GPU, so you might see a tremendous speedup on 600 series,
but that is quite speculative.

OpenCL is ~equivalent, or even faster than CUDA for OpenMM/GROMACS. OpenCL
used to be much slower, but there have been a lot of improvements. That
being said, I don't know that Radeon cards are necessarily faster than
nVidia cards for OpenMM/GROMACS.

Two points I would make, maybe they aren't relevant to your particular
situation, but in case others find this thread:

1) If you are going to get the 600 series GTX cards, and you want to use
NAMD, you should really get a motherboard that supports PCI-E 3.0 rather
than 2.0. This is because the new GTX680 actually has only 256-bit
bandwidth compared to 384-bit for the GTX580, but PCI-E 3.0 allows double
the transfer rate compared with 2.0, so you actually come out ahead. For
AMBER or OpenMM/GROMACS I'm not sure this is that critical, but for NAMD,
because the tasks are split between the CPU and GPU, you need communication
every step, and so that bandwidth is likely the limiting performance factor--00163662e5ea10dc0b04c14191d5--

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