[gmx-users] GPU and aux power supply

Szilárd Páll pall.szilard at gmail.com
Thu Jul 2 02:09:03 CEST 2015 

Hmmm, 8x sounds rather high, are you sure you are comparing to CPU-only
runs that use proper SIMD optimized kernels?

Because of the way offload-based acceleration works, the CPU and GPU will
inherently be executing concurrently only part of the runtime and as a
consequence the GPU is idle part of the run-time (during
integration+constraints). You can make use of this idle time by running
multiple independent simulations concurrently. This can yield serious
improvements in terms of _aggregate_ simulation performance especially with
small inputs and many cores (see slide 51 https://goo.gl/7DnSri)/

--
Szilárd

On Wed, Jul 1, 2015 at 4:16 AM, Alex <nedomacho at gmail.com> wrote:

>  I am happy to say that I am getting an 8-fold increase in simulation
> speeds for $200.
>
>
> An additional question: normally, how many simulations (separate mdruns on
> separate CPU cores) can be performed simultaneously on a single GPU? Say,
> for 20-40K particle sized simulations.
>
> The coolers are not even spinning during a single test (mdrun -ntomp 4),
> and I get massive acceleration. They aren't broken, the card is just cool
> (small system, ~3K particles).
>
>
> Thanks,
>
>
> Alex
>
>
>
>   >
>
>
>
>
>   >
>
> Ah, ok, so you can get a 6-pin from the PSU and another from a converted
> molex connector. That should be just fine, especially as the card should
> will not pull more than ~155W (under heavy graphics load) based on the
> Tomshardware review* and you are providing 225W max.
>
>
>
> *
> http://www.tomshardware.com/reviews/evga-super-super-clocked-gtx-960,4063-3.html
>
>
>
>
> --
>
> Szilárd
>
>
>
> On Tue, Jun 30, 2015 at 7:31 PM, Alex <nedomacho at gmail.com> wrote:
>
>
> Well, I don't have one like this. What I have instead is this:
>
>
> 1. A single 6-pin directly from the PSU.
>
> 2. A single molex to 6-pin (my PSU does provide one molex).
>
> 3. Two 6-pins to a single 8-pin converter going to the card.
>
>
> In other words, I can populate both 6-pins on the 6-8 converter, just not
> sure about the pinouts in this case.
>
>
> Not good?
>
>
> Alex
>
>
>
>   >
>
> What I meant is this: http://goo.gl/8o1B5P
>
>
> That is 2x molex -> 8pin PCI-E. A single molex may not be enouhg.
>
>
>
> --
>
> Szilárd
>
>
>
> On Tue, Jun 30, 2015 at 7:10 PM, Alex <nedomacho at gmail.com> wrote:
>
>
> It is a 4-core CPU, single GPU box, so I doubt I will be running more
>
> than one at a time. We will very likely get a different PSU, unless...
>
> I do have a molex to 6 pin concerter sitting on this very desk. Do you
>
> think it will satisfy the card? I just don't know how much a single
>
> molex line delivers. If you feel this should work, off to installing
>
> everything I go.
>
>
> Thanks a bunch,
>
> Alex
>
>
> SP> First of all, unless you run multiple independent simulations on the
> same
>
> SP> GPU, GROMACS runs alone will never get anywhere near the peak power
>
> SP> consumption of the GPU.
>
>
> SP> The good news is that NVIDIA has gained some sanity and stopped
> blocking
>
> SP> GeForce GPU info in nvidia-smi - although only for newer cars, but it
> does
>
> SP> work with the 960 if you use a 352.xx driver:
>
> SP> +------------------------------------------------------+
>
>
> SP> | NVIDIA-SMI 352.21     Driver Version: 352.21         |
>
>
> SP>
> |-------------------------------+----------------------+----------------------+
>
> SP> | GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile
> Uncorr.
>
> SP> ECC |
>
> SP> | Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util
> Compute
>
> SP> M. |
>
> SP>
> |===============================+======================+======================|
>
> SP> |   0  GeForce GTX 960     Off  | 0000:01:00.0      On |
>
> SP>  N/A |
>
> SP> |  8%   45C    P5    15W / 130W |   1168MiB /  2044MiB |     31%
>
> SP>  Default |
>
> SP>
> +-------------------------------+----------------------+----------------------+
>
>
>
> SP> A single 6-pin can deliver 75W, an 8-pin 150W, so in your case, the
> hard
>
> SP> limits of what your card can pull is 75W from the PCI-E slow + 150W
> from
>
> SP> the cable = 225 W. With a single 6-pin cable you'll only get ~150W max.
>
> SP> That can be OK if your card does not pull more power (e.g. the above
>
> SP> non-overclocked card would be just fine), but as your card is
> overclocked,
>
> SP> I'm not sure it won't peak above 150W.
>
>
> SP> You can try to get a molex -> PCI-E power cable converter.
>
>
>
> SP> --
>
> SP> Szilárd
>
>
>
> SP> On Mon, Jun 29, 2015 at 9:56 PM, Alex <nedomacho at gmail.com> wrote:
>
>
> >> Hi all,
>
> >>
>
> >> I have a bit of a gromacs-unrelated question here, but I think this is a
>
> >> better place to ask it than, say, a gaming forum. The Nvidia GTX 960
> card
>
> >> we got here came with an 8-pin AUX connector on the card side, which
>
> >> interfaces _two_ 6-pin connectors to the PSU. It is a factory
> superclocked
>
> >> card. My 525W PSU can only populate _one_ of those 6-pin connectors. The
>
> >> EVGA website states that I need at least 400W PSU, while I have 525.
>
> >>
>
> >> At the same time, I have a dedicated high-power PCI-e slot, which on the
>
> >> motherboard says "75W PCI-e". Do I need a different PSU to populate the
> AUX
>
> >> power connector completely? Are these runs equivalent to drawing max
> power
>
> >> during gaming?
>
> >>
>
> >> Thanks!
>
> >>
>
> >> Alex
>
> >> --
>
> >> Gromacs Users mailing list
>
> >>
>
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>
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>
> >> posting!
>
> >>
>
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>
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>
> >>
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>
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>
>
> --
>
> Best regards,
>
>  Alex                            mailto:nedomacho at gmail.com
> <nedomacho at gmail.com>
>
>
>
>
>
> --
>
> Best regards,
>
>  Alex                            mailto:nedomacho at gmail.com
> <nedomacho at gmail.com>
>
>
>
>
>
> --
>
> Best regards,
>
>  Alex                            mailto:nedomacho at gmail.com
> <nedomacho at gmail.com>
>
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