Nvidia limiting gtx680 compute speed?

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Dade
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Re: Nvidia limiting gtx680 compute speed?

Postby Dade » Tue Mar 27, 2012 12:42 pm

spectral wrote:About OpenCL performance,

Have you introduce a bug in the partners.nvidia.com web site ? I'm sure that if you introduce an issue and an example (SLG...) they will give you some feedback and improve it !


It isn't a bug or a SLG specific problem, it is one of their latest driver release to have cut the performance of most OpenCL applications. Their OpenCL forum has multiple threads reporting this problem.

Dade
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Re: Nvidia limiting gtx680 compute speed?

Postby Dade » Tue Mar 27, 2012 7:31 pm

Blender/Cycles (i.e. CUDA path tracer) users report that the 580GTX is faster than the 680GTX too.

It is just worser at running that kind of tasks; probably by design. Merax's post (with the link provided) has the best explanation I have seen up to now.

dsavi
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Re: Nvidia limiting gtx680 compute speed?

Postby dsavi » Thu Mar 29, 2012 8:31 am

Merax wrote:I don't think it's a conspiracy, just changing design goals that resulted in less bandwidth per compute unit.

When you see benchmark results like those, it makes you wonder...

I guess I'll be switching to AMD on my new build.

toxie
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Re: Nvidia limiting gtx680 compute speed?

Postby toxie » Thu Mar 29, 2012 3:36 pm

Rest assured that there will be something worth the wait on http://code.google.com/p/understanding- ... l-on-gpus/ (as usual) soon.. As i said earlier, 680 was mainly designed for more perf/watt, especially in games, but it doesn't mean that ray tracing is slow in general..
Better you leave here with your head still full of kitty cats and puppy dogs.

toxie
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Re: Nvidia limiting gtx680 compute speed?

Postby toxie » Thu Mar 29, 2012 4:54 pm

Okay, seems i was wrong with the addy, for now it's only available from here: http://www.tml.tkk.fi/~timo/HPG2009/index.html :)
(and actually the results are quite amazing, too, at least for this kind of pure, raw ray tracing performance!)
Better you leave here with your head still full of kitty cats and puppy dogs.

Vilem Otte
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Re: Nvidia limiting gtx680 compute speed?

Postby Vilem Otte » Fri Mar 30, 2012 1:13 am

Wonder how they actually get that high numbers (noticed they've got code, yummy ... gotta walk through it during the weekend). On GPU I still get "just" some 10 MRays/s (for primary) in naive (meaning like no packets or stuff) implementation of KDtree ray tracer on Radeon HD 6770 (not the best card, but I think I should get some 5 - 10 times more, still I know that my code is heavily unoptimized) ... ofc I'm just getting into OpenCL (but I smell some sorcery in my code).

toxie
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Re: Nvidia limiting gtx680 compute speed?

Postby toxie » Fri Mar 30, 2012 10:38 am

Its the small details that they have (you really should read the paperand comments on the page), plus i think they have the benefit of the BVH on Kepler.. But i'll have to run some tests myself to judge if othe stuff (kD/BIH) can profit, too.. Plus CUDA, which usually is the better choice on NVIDIA hardware..
Better you leave here with your head still full of kitty cats and puppy dogs.

spectral
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Re: Nvidia limiting gtx680 compute speed?

Postby spectral » Fri Mar 30, 2012 2:50 pm

Interesting,

Does someone test the performance of the Kepler_kernel... on fermi.

And compared the performance of kepler_speculative_while_while.cu vs fermi_speculative_while_while.cu, to check if fermi also benefit of some changes (It seems that they also do some other changes, but not sure they are related for Kepler) ?
Spectral
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toxie
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Re: Nvidia limiting gtx680 compute speed?

Postby toxie » Fri Mar 30, 2012 4:26 pm

the other changes are minimal, its mainly changing the amount of tris processed per pass from one to two, and replacing some fminf's with integer variants..
Better you leave here with your head still full of kitty cats and puppy dogs.

madd
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Re: Nvidia limiting gtx680 compute speed?

Postby madd » Fri Mar 30, 2012 8:19 pm

What's the best performance that can be achieved for the fastest Intel CPUs for AO rays in conference room?


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