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Message boards : Graphics cards (GPUs) : SLI speeds for two cards? x16 vs 2@x8

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Message 27327 - Posted: 17 Nov 2012 | 21:28:40 UTC

I was considering adding a second GTX260 to my system but ran across what might be an issue with my MOBO. I see the PCIe 2.0 x16 has either one slot at x16 or two at x8. I didn't consider a board with two x16 at the time so short of buying a new MOBO could I add a second GTX 260 and have appreciable WU output improvement with two running at x8? I'm not entirely sure what the x16 and x8 signify so I was unsure how substantial their impact is on WU completion. Will both cards run at half speed with x8 slots? Thanks!

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Message 27331 - Posted: 18 Nov 2012 | 10:20:20 UTC - in response to Message 27327.

Yes, you could add a second and crunch on both. The loss from dropping to PCIE2.0 x8 would be minimal on your fist GPU. On newer high end cards it would be more noticeable.
You don't seem to use the first much to crunch with. So why another?

I suggest you look to the GF600 range for a replacement card, rather than adding another GTX260. Getting a good GTX260 was always difficult and running two in the same system would have it's own problems; heat, noise, power consumption (bigger electric bill and might require a new PSU).


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Message 27334 - Posted: 18 Nov 2012 | 11:23:03 UTC

Totally agree with SK: don't get another GTX260 now, compared to current cards it's practically ancient. It's consuming quite some power (=running costs) in idle and under load.

Even a GTX650Ti significantly outperforms a GTX260, while drawing around half the power. GTX660Ti is faster by another 75%, but also ~75% more power hungry, of course. Both are excellent value for crunchers. And will remain useful for much longer than an older card (support of newer features etc.).

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Message 27338 - Posted: 18 Nov 2012 | 22:48:16 UTC

Those are both great points. After looking up some benchmarks it's painfully clear how outdated this 260 is. It feels like I just bought it; it's amazing what two years does in technological improvement. My RAC is so low because I had to reallocate the GPU to a project with lower requirements as WU's from GPUGRID were taking just too long (typically 3-4 days). That should have been my first hint it was time to update.

As far as upgrading goes what would make the 660 Ti a better purchase than say a GTX 580 or GTX 670 with comparable benchmark scores and within the same price range? Will I have any problems utilizing these boards with a two year old MOBO? I am currently running a P7P55D-E motherboard with first gen i-5 CPU although I plan on upgrading those as well in the near future.

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Message 27341 - Posted: 19 Nov 2012 | 8:21:52 UTC - in response to Message 27338.
Last modified: 19 Nov 2012 | 8:24:49 UTC

gtx 580 will have a much higher power usage. GTX 670 will have practically the same output in GPUGrid but at a slightly higher purchase price.

they work fine in the first-gen i-series motherboards, but upgrade to sandy/ivy bridge ASAP as the power usage and heat output is so much lower! i would say make sure there is a minimum of pci-e 2.0 x8 slot available though. if pci-e 1.0 only, then need to have x16 slot IMO
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Message 27351 - Posted: 19 Nov 2012 | 15:25:01 UTC

Great information everyone, thanks. Looks like ill be picking up my new card this weekend. Cant wait to get crunching again.

Out of curiosity, you mentioned that all of the three GPU's would perform similarly for GPUGRID. Does this performance comparison between cards vary for different BOINC projects? I never quite found a way for measuring benchmark performance for GPU/CPU's against projects.

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Message 27362 - Posted: 19 Nov 2012 | 22:03:56 UTC

That performance question is tricky and a general answer is difficult. It always boils down to "it depends on the code you run", hence is difficult (or downright impossible) to capture in a single benchmark.

However, some things are clear: GTX660Ti has got exactly the same raw horse power as a GTX670. The difference is a reduction to 3/4 th the memory bandwidth on the small card. this hurts gaming performance enough to warrant the price difference, but doesn't affect most BOINC crunching. Actually not a single project I know of. Weird move of nVidia.. but good for us :)

Comparing to the GTX580 is more difficult, as the architecture has been changed significantly. In short: the GTX580 has less raw horse power, but can use more of it - which ends up with an approximate tie in performance in most projects. It pays for this with a conceptually higher power consumption, as well as the older process technology.

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Message 27387 - Posted: 23 Nov 2012 | 18:24:14 UTC

Sorry for my English, I'm from Russia.
I HAS GTI 660 TI from Gigabyte, and has test it on some projects on my Intel Z68 motherboard with two 16x8 PCIE slots. I bring in one GTX 560TI Gig, fnd one GTX 660 Gig. In GPUGRID, E@H and Milkiway@H GTH560TI was faster, then apponent.
Because GTX6XX's processors works at lower frequecy. I have tested it at gamer's banchmarks - its fine, but not for computing. I take it back, add small cash, and bye HD7900...

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Message 27388 - Posted: 23 Nov 2012 | 18:40:06 UTC - in response to Message 27387.

Hello: Milkiway is a Double Precision task, is the only think that at this time there in Boinc.

The GTX600 series are not good in DP in this case are better GTX500 and AMD / ATI. Greetings.

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Message 27389 - Posted: 23 Nov 2012 | 18:54:22 UTC - in response to Message 27388.

ATi HD7950 does it (MW@H) for 58 secs. 560 TI - about 5-6 minutes, Number of processors... But in Einshteih@H GTX560 works faster, that HD7900.

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Message 27396 - Posted: 24 Nov 2012 | 0:52:36 UTC - in response to Message 27389.
Last modified: 24 Nov 2012 | 1:05:30 UTC

GPUGrid doesn't use AMD/ATI cards.
The GTX660Ti is faster than a GTX560Ti here and probably at Poem.
You can get a RAC of ~315K here from one GTX660Ti and a RAC of ~215K from a GTX560Ti.
At Einstein and Albert the GeForce cards are generally better than the AMD/ATI cards.
At MW the AMD cards are best, but some are much better than others (dp/FP64).
At Poem the AMD 5800 cards slightly outperform their GeForce 400 counterparts, some of the GF500 cards are roughly on par, and even fair reasonably against the best 6000's. I think the AMD 7000's and GF600's are roughly on par.
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