Hello everyone,

So I am considering buying a 2nd GTX 970 to help with my average; I was going to run them in SLI.

I was researching if there would be any problems in crunching SETI tasks in SLI, and it appears that there were issues, but the most recent topic I could find was from 2009.

Is this something that is now possible? Or should I avoid SLI for crunching?

Thanks!

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It makes not one whit of difference. Whether you mount your GPUs in SLI or not, SETI/BOINC will treat them as two separate, independent, GPUs.

The only problem is that SLI will tie their speeds together. If one GPU gets warmer than the other, and needs to throttle back, the cool one will be throttled back too.

Thank you for the quick response and information :)

So, it does sound like I would get a decent boost with a 2nd 970, but it wouldn't exactly be 2x as much as I'm getting with 1 970 because of diminishing returns (as they will both be tied to the same speed)?

Sounds like it might still be worth it then. I'll probably be doing it either way to be ready for VR in 2016, so any improvement to my RAC will just be a bonus. I basically just wanted to make sure that I would be getting some sort of gain.

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Experience says that running a pair of identical GTX970 wit SLI resulted in a <10% hit over running the same two, in the same PC, without SLI.
Adding a second (identical) GPU to a PC running both CPU and GPU will not double the RAC of the machine, but will almost double the GPU contribution on the proviso that you free-up double the number of CPU cores.
Don't forget that the CPU is only contributing about 1k per core in use, while each GTX970 will be doing 20k-25k


(take a look at the figures for this PC of mine: http://setiathome.berkeley.edu/show_host_detail.php?hostid=7619589 - it is currently doing about 59k, compared to ~58k from a dual GTX980 PC whose GPUs cost twice as much!)

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Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

This is good information, thanks to everyone. I am planning to get a couple of GTX 970s for my new rig. Would there be any difference in using the mini ITX version compared to the regular ones?

...the ability to cool them might restrict how hard you can push them, but otherwise there should be no limitations.
Personally I would not try to overclock these cards, and may even consider down clocking.

ITX cases are very restricted on their airflow capacity hence their cooling ability, so don't try to overclock the cards, and do make sure the PSU is up to the task - again a known limitation on these physically smaller cases.

(I had a "full size" and "reduced size" 460 in the same PC a few years back and the reduced size card ran hotter regardless of which pair of slots were in use and in which order the two cards were inserted.)

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Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

Experience says that running a pair of identical GTX970 wit SLI resulted in a <10% hit over running the same two, in the same PC, without SLI.
Adding a second (identical) GPU to a PC running both CPU and GPU will not double the RAC of the machine, but will almost double the GPU contribution on the proviso that you free-up double the number of CPU cores.
Don't forget that the CPU is only contributing about 1k per core in use, while each GTX970 will be doing 20k-25k


(take a look at the figures for this PC of mine: http://setiathome.berkeley.edu/show_host_detail.php?hostid=7619589 - it is currently doing about 59k, compared to ~58k from a dual GTX980 PC whose GPUs cost twice as much!)

Your dual 980's should be hitting at least 70k. something must be astray with your configurations.

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The dual 980 rig does a lot of other work, like earning money processing large cfd models for hours on end....

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Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?