[gmx-users] info about gpus

[Moir, Michael (MMoir)]

Sorry, that's 32 GB of RAM.  I'm old, a MB used to be a lot of memory!

Mike

-----Original Message-----
From: gromacs.org_gmx-users-bounces at maillist.sys.kth.se <gromacs.org_gmx-users-bounces at maillist.sys.kth.se> On Behalf Of Moir, Michael (MMoir)
Sent: Thursday, January 31, 2019 6:29 PM
To: 'gmx-users at gromacs.org' <gmx-users at gromacs.org>
Subject: [**EXTERNAL**] Re: [gmx-users] info about gpus

Stephano,

With a motherboard that doesn't split the PCI-E bandwidth, I get a 20% improvement in computation speed with 2 GPUs.  Whether or not you think this is worth the extra $, I leave that up to you!  My system is:  i9-9900K, ASUS WS Z390 Pro motherboard, 2x 1070ti GPUs, 32 MB 3200 MHz RAM.  With my modest system of about 100,000 atoms, I go from 30 ns/day with 1 GPU, to 36 ns/day with 2 GPUs.  -ntmpi 4 -npme 1 -pme gpu -nb gpu, all other combinations of -ntmpi give inferior results with 2 GPUs compared to 1 GPU.  I am using Gromacs-2019.  It is also important to use the fastest memory you want to afford.  The amount of memory is not important but the speed is.

Mike

-----Original Message-----
From: Moir, Michael (MMoir) 
Sent: Thursday, January 31, 2019 9:44 AM
To: gmx-users at gromacs.org
Subject: RE: [**EXTERNAL**] [gmx-users] info about gpus

Stefano,
I'm investigating that myself.  If your motherboard splits the bandwidth between your PCI-E slots then there is no advantage to having 2 GPUs for a GPU like the 1080.  I have just upgraded to a better motherboard that does not split the  bandwidth but I am not finished my testing.  Going to the 2080 offers a 40% increase in speed over the 1080 in terms of raw computing power but it is unclear that it is worth the extra $.
Mike

-----Original Message-----
From: gromacs.org_gmx-users-bounces at maillist.sys.kth.se <gromacs.org_gmx-users-bounces at maillist.sys.kth.se> On Behalf Of Stefano Guglielmo
Sent: Thursday, January 31, 2019 9:14 AM
To: gromacs.org_gmx-users at maillist.sys.kth.se
Subject: [**EXTERNAL**] [gmx-users] info about gpus

 Dear all,
I am tryin to set a new workstation and I would like to know if there is a
significant improvement in performance with two gpus (gtx 1080 ti or rtx
2080) rather than just one, and eventually with which cpu/ram requisite.

Thanks in advance for any advice and suggestions
Stefano

-- 
Stefano GUGLIELMO PhD
Assistant Professor of Medicinal Chemistry
Department of Drug Science and Technology
Via P. Giuria 9
10125 Turin, ITALY
ph. +39 (0)11 6707178


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