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Nvidia SLI - wonderings about fps increases and reliability

TheBigCheese

TheBigCheese

TheBigCheese

Soldato
Joined
6 Sep 2005
Posts
3,781
Hi everyone

I've just had a little splurge recently and am now typing this looking at a 40" 4K display and a new 970GTX to run it.

It's a speedy card no question, but I am finding (as expected) that it does need more umph to get decent frame rates.

Playing Far Cry 3 at ultra settings on full 4K I am getting frame rates around 20-25fps, not bad for what it has to do but it's chugging (surprisingly dropping the detail settings makes no difference, except for AA, that kills it!).

Dropping the resolution down a couple of notches pushes it beyond 70fps on ultra which I think is quite stunning.

So...full 4K at full quality...can I expect a second 970 to double, or closely double the frame rates, or doesn't it work quite that way?

Btw, I'm not an extreme overclocker or bencher, 60fps is all I'm looking for.

I'm also wondering about video rendering which can take advantage of CUDA processes, will that benefit from SLI?

Do all games benefit from it or do they have to be specifically coded to take advantage of SLI?

I haven't looked at this for years so I'm completely out of the loop with it!

Looking forward to your replies!
 
I think the term your looking for is scaling, if it was to double your FPS then that means that game or for now we will call it Farcry 3 would have 100% SLI scaling on two cards. No one can say for sure if it will double your FPS sometimes games are not optimised very well which results in no SLI compatibility or poor scaling. Depends from game to game mate. As im not sure of farcry 3's scaling capabilities i cannot comment sorry.
 
There's also the issue of VRAM. At 4K with high levels of AA you may be running out of VRAM. It seems you have found this the hard way! A second card won't help you there - the only solution is to reduce the levels of AA. Texture mods can also eat VRAM.
 
As mentioned some games have better scaling than others. Tomb Raider for example has excellent scaling. There are also some games that have 0 scaling such as id tech 5 titles like Wolfenstein.

If you can get 70%+ scaling then you are doing well imo :)

I gave FC3 a try on Ultra at 4K with 2xMSAA and was getting 40-55fps wandering around on the err house at top of the hill with the green house etc. VRAM usage was only around 2700MB.
 
Thanks for the replies chaps, that's really helpful!

Scaling sounds exactly right r7slayer, I can find a lot more information on the net now I know the proper term for it! :D

I certainly have found that Quartz, as I read before I moved to 4K, AA isn't really needed or make much of a difference due the the amount of pixels in the image, I certainly haven't noticed much of a difference except for the stuttering, it didn't look any less jagged with the AA on.

Thanks stooeh, that's really helpful as well. Is there any comprehensive chart anywhere showing the gains with SLI in games / applications? I'm surprised that the ID tech 5 engine doesn't make use of SLI at all, they were always as the forefront of driving graphics forward. That's doubly a shame about Wolfenstein, it's one of my favourite games!

That sounds good, especially as you're running SLI 970's! Now I've moved to a bigger screen I'm really noticing the jumpy movement at 30fps so I think I really need to be getting 60fps to remove that, it certainly seems smooth at 70fps!

In my system currently I'm running:

i7 3770K (stock)
Gigabyte Z77-D3H
32GB RAM
970GTX
BR Burner
x2 SSD
x5 HDDs
Various fans

All on an Enermax 620W PSU. I've read that for SLI I would need to go higher, the EVGA PSUs seem to have very good reviews, I was looking at an 850W, would that be enough with the efficiency of these cards? I was looking at a Youtube video that tested x4 SLI 980GTX on a 1.5KW PSU and it was only drawing around 650W! :eek:

Finally...the SLI bridge that comes with the motherboard...is that a necessary component or can they just run through the PCI lanes? I can't find the bridge anywhere! :(
 
TheBigCheese said:
All on an Enermax 620W PSU. I've read that for SLI I would need to go higher, the EVGA PSUs seem to have very good reviews, I was looking at an 850W, would that be enough with the efficiency of these cards? I was looking at a Youtube video that tested x4 SLI 980GTX on a 1.5KW PSU and it was only drawing around 650W! :eek:
Click to expand...

The 9x0 cards use much less power than prior generations. You should be okay on your 620W PSU.

Finally...the SLI bridge that comes with the motherboard...is that a necessary component or can they just run through the PCI lanes? I can't find the bridge anywhere! :(
Click to expand...

Yes, SLI bridges are still necessary - it's Crossfire that doesn't use them any more - but I've read that you need a v2 SLI bridge for 4K, so your old one may not work anyway.
 
Yeah I read that GTX 970 SLI is about 500w max. Just got myself GTX 970 SLI and I am finding it fab so far. My benchmarks in like 3DMark have gone up by about 50%. Games are more fluid than when I had the single gtx 980. I played Operation Flashpoint Red River yesterday and had everything on max and just turned off AA for 4k it was very smooth. Although I do have gsync helping. Be interesting when I get round to more newer titles I need to play, eg Borderlands Prequel, CODAW and Shadow of Morder.
 
Thanks for the replies guys, that's really useful.

A v2 SLI bridge? Ah hell...that's not good, I'm having a look up about that now, see if I can find anything about it...there doesn't seem to be bridges generally available that don't come with motherboards. :(
 
Hmmm, I can't seem to find anything about a new bridge or compatible 4K bridge. All I can see is that Evga is making a 'Pro' range of bridges that seem to light up when connected to Titans and cost an arm and a leg...nothing mentioning what else they actually do though.
 
I've never heard of a V2 bridge...

All the SLI bridge does it connect the pins of the SLI connectors. There is no active processing going on.
 
Thanks for the replies guys, that's really helpful!

I think with the amount of HDDs I run and disc burning the 620W may be pushing it, I'll see how it goes.

Ah, glad it's not just me not hearing about an SLI bridge, I'll cross my fingers on that front I think!


Disco_P said:
Might also want to look into overclocking that CPU. It's super easy to do and couldn't hurt.
Click to expand...

I would actually really like to do that, it has a stonking great heatsink and fan on it for that purpose but I've never actually done it...I haven't a clue how to be honest and it seems a bit complicated with setting RAM etc.

Know any idiot resistant guides? :D
 
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