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SLI x2; x3 and x4

Post Date: 2014-10-22

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Dax Doomslayer View Drop Down
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  Quote Dax Doomslayer Quote  Post ReplyReply bullet Topic: SLI x2; x3 and x4
    Posted: 22 Oct 2014 at 6:55am
Hi Folks,
I was wondering if the illuminati of this board can enlighten me.  Everything I've been reading is that x2 SLI is really the sweet spot.  Anything beyond that has rapidly diminishing returns to the point where x4 basically contributes next to nothing.  Would it be wiser to do something as x2 and then use one of the cards as a PhysX card?  I'm curious as to what people think about this and really what they'd feel is a wise investment.  Sorry for the dumb question.  Thanks!!

PS:  Bprat, I'm sure you'll show up in this thread - congrats on 10K posts!!
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  Quote bprat22 Quote  Post ReplyReply bullet Posted: 22 Oct 2014 at 9:15am
Hey Dax.... Thanks,   Appreciate it.  Big%20Smile

Scaling of video cards definitley favors less cards.    A general rule, at least a couple of years ago, was the 2nd card gave you about 80% more, the 3rd card about another 30-40% and the 4th little or nothing.    I think 4K even scales with a little less than that.

But, this is all so game dependant, with some games doing better.  

If you mean a tri sli vs 2x sli + PhysX, I'd go tri-sli.   Physx from my limited research is a strange animal.  It helps with some games and actually hurts fps in others.  PhysX, to me, would be a sli setup and an older card just laying around and used for PhysX .  Usually can't hurt.

Just me since I can't link any proof.  Big%20Smile


Nav has posted under Video cards some setups that compare and they run somewhat to what i said.  Here's one to check out.   

http://www.digitalstormonline.com/unlocked/nvidia-geforce-gtx-780ti-2x-3x-4x-sli-overclocking-benchmarks-idnum117/

He has a couple of other here. 






Edited by bprat22 - 22 Oct 2014 at 9:20am
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Dax Doomslayer View Drop Down
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  Quote Dax Doomslayer Quote  Post ReplyReply bullet Posted: 22 Oct 2014 at 10:28am
Thanks for the link.  I was asking if it was x2+PhysX vs. x3 SLI was a better set up. So x3 sounds like the way to go then.  There's minimal gain with x4 considering the cost.  I wonder how the 980s scale - I would think probably in a similar manner.  Would the x99 platform make a difference due to the better bandwidth on the higher end MBs?
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  Quote bprat22 Quote  Post ReplyReply bullet Posted: 22 Oct 2014 at 11:00am
The X99 uses the same 40 lanes from the cpu as the X79.   I don't think that has changed.  With the 5820k cpu on X99 you'd get 24 lanes of Pcie at x8x8x8 lanes and the 5930k you get 40 lanes at x16x16x8, but I have never seen any benches that show a x16 3rd gen performs any better than a x8 3rd gen, maybe a frame or two difference.   I'm sure that day will come but not yet, from my checking.  Big%20Smile
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  Quote Dax Doomslayer Quote  Post ReplyReply bullet Posted: 22 Oct 2014 at 1:04pm
From what I've read, I agree with you.  The x16 doesn't seem to provide gains which is odd.  Would that be a hardware thing or a driver thing?
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  Quote bprat22 Quote  Post ReplyReply bullet Posted: 22 Oct 2014 at 1:08pm
Hardware. Today's cards just aren't saturating the x8 bandwidth.
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  Quote Meller Quote  Post ReplyReply bullet Posted: 22 Oct 2014 at 1:18pm
Keep in mind that newer cards offer better scaling when it comes to sli. I'm assuming we're only talking about nvidia here. AMD actually has offered much better scaling in terms of multi gpu set ups for a good while now.

In my opinion, the 3 gpu set up is the sweet spot for max performance vs price ratio (when we're talking about 1,2,3 & 4 card set ups.

But the new GTX 980 actually overs some great scaling all the way up to 4 cards. But, as per my previous statement, the 3 card GPU is really the sweet spot. It's the last spot you see some good jumps.

Now Bprat is right. You're going to be getting like 80% with a second card and about 50% with a third. I say third is the sweet spot because 50% is a big jump compared to say 10-20% for a 3rd to 4th.

As far as PCI lanes go. We don't have any cards in todays consumer marker that use up 40 lanes. Hell, the difference between a x16 and x8 is like 1-2 fps usually.

Basically it depends on the card on how many you'll want. a GTX 760 is a great card and two of them are amazing. But I wouldn't buy three. While a GTX 780 is an amazing card all the way up to three, but I wouldn't buy a 4th. A GTX 980... I'd buy at very least 3... and come better drivers possibly a 4th just because scaling is getting so good finally.

*This is under the assumption that the game profiles nicely with sli set ups*
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  Quote Dax Doomslayer Quote  Post ReplyReply bullet Posted: 23 Oct 2014 at 6:56am
Wow - I didn't realize the 3rd card gave that big of a jump.  When I was reading, it didn't seem that much.  I'll probably be going x3 980s is what I'm thinking unless something else comes out prior to around Thanksgiving.  Thanks for the input folks.  It is greatly appreciated.
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  Quote Meller Quote  Post ReplyReply bullet Posted: Today at 6:21am
It didn't at first. At the very start of the GTX 980 release, it was just barely beating the GTX 780, with the GTX Titan Black and GTX 780 Ti out performing it. Now, in a single card set up, the GTX 980 wins at 1080p, 1440p, and just barely at 4k over all the cards.

And drivers are just starting to mature, so it's definitely getting better and better with scaling. Keep that in mind. Performance continue to only get better. Especially with DSR support, which I personally have tested, and it works amazingly.
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  Quote Dax Doomslayer Quote  Post ReplyReply bullet Posted: Today at 8:03am
Thanks Meller.  That's what I was seeing too thus why I was surprised at what you indicated with x3 SLI.  Nothing I saw (albeit this was early on) indicated that x3 really had significant gains.  I appreciate the update and drivers maturing is one thing that I didn't consider.
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  Quote Meller Quote  Post ReplyReply bullet Posted: Today at 8:52am
Oh yea. 3 is the cap right now in terms of sweet spot. Now in just general terms of performance jumps, yes two in sli wins. But in terms of getting noticeable performance jumps... 3 is where it really stops. Three is, in my opinion, the current sweet spot for performance gains.
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