Re: Three GPU cards on shared-mem motherboard

From: Axel Kohlmeyer (
Date: Wed May 30 2012 - 20:02:31 CDT

On Wed, May 30, 2012 at 8:50 PM, Aron Broom <> wrote:
> I'm not aware of any motherboards that have 3 PCI-E 3.0 slots yet, there
> appear to be some with 2.  I haven't looked very hard, I imagine in a year
> or so it will be more common.
> To reiterate something someone else mentioned, I believe the 690, much like
> the 590, is just two 680 cards together.  It also, therefore, needs two
> PCI-E slots for the one card.  In the case of the 500 series cards, I found

this is incorrect. both the GTX 690 and the GTX 590
(as well as the GTX 290) only need a single PCI-e slot
(double though). the two GPUs are placed behind a
PCI-e bridge and thus have to share the available
bandwidth when used both. so this sense they are
similar to (server) mainboards that offer a lot (i've seen
them with up to 8) of "full" 16-lane PCIe slots.


> the 570 performed at about 85% of the 580 on a 6-cpu-core system with a
> 100k atom system being simulated in NAMD, but the price was ~66%.  I'm not
> sure if this will be true for the 670.
> As a final note, there has been some attention on the fact that the latency
> (which particular latency I'm not sure) on the 600 series is higher, but
> that for games that is more than counterbalanced by the additional cores.
> It's not clear to me that this would be the case necessarily for MD, so I
> would really urge trying to find some avid gamer with a 670 or 680 and
> getting them to do a quick benchmark before investing in those cards.
> ~Aron
> On Wed, May 30, 2012 at 1:33 PM, Francesco Pietra <>wrote:
>> Forgot the list previously. Sorry
>> f.
>> ---------- Forwarded message ----------
>> From: Francesco Pietra <>
>> Date: Wed, May 30, 2012 at 7:28 PM
>> Subject: Re: namd-l: Three GPU cards on shared-mem motherboard
>> To: Vincent Leroux <>
>> On Wed, May 30, 2012 at 6:14 PM, Vincent Leroux <>
>> wrote:
>> > Hi,
>> >
>> > A GTX690 basically is two GTX680 chips on a single board. No surprise,
>> this
>> > is twice as expensive. You may have a hard time finding one on the
>> market.
>> > In addition, I am not sure you can put more than two on a single
>> > motherboard, this may be technically impossible. And if you have two you
>> > have to make sure the motherboard design leaves enough space between the
>> two
>> > cards, if they are too close the top one will probably die very quickly

Dr. Axel Kohlmeyer
College of Science and Technology
Temple University, Philadelphia PA, USA.

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