Re: PCIexpress 3.0 for MD with NAMD on GPUs

From: Thomas Albers (
Date: Sat Nov 16 2013 - 09:58:22 CST


> Which version of the nvidia driver is needed to activate PCIexpress 3.0
> between the GPUs and RAM for MD with NAMD2.9 or NAMD2.10? As far as I can
> remember, nvidia deactivated PCIe 3.0 for linux from version 295.xx until
> at least 310.xx. Is that correct?

I am using an i5-Ivy Bridge CPU and a GTX 660 GPU with Nvidia driver
304.43 and can confirm that PCI-e 3.0 works. (I have not done
benchmarking to see if there is any speedup compared to PCI-e 2.0.)

# cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 58
model name : Intel(R) Core(TM) i5-3570 CPU @ 3.40GHz

# cat /proc/driver/nvidia/version
NVRM version: NVIDIA UNIX x86_64 Kernel Module 304.43 Sun Aug 19
20:14:03 PDT 2012
GCC version: gcc version 4.5.4 (Gentoo 4.5.4 p1.0, pie-0.4.7)

# lspci -vvvv
01:00.0 VGA compatible controller: nVidia Corporation Device 11c0 (rev
a1) (prog-if 00 [VGA controller])
        Subsystem: ZOTAC International (MCO) Ltd. Device 1281
        LnkSta: Speed 8GT/s, Width x16, TrErr- Train- SlotClk+
DLActive- BWMgmt- ABWMgmt-

What the driver does is fall back to PCi-e 2.0 when not under load, so
one has to check while crunching numbers on the GPU. If the GPU is
idle it reports a 5 GT/s transfer rate. I do not know if this
behaviour is peculiar to Nvidia or part of the PCI-e standard.

Hope that helps,

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