SLI Setup and Testing Configuration
We got our hands on a set of GTX 980 reference cards to run through paces in 3-Way and 4-Way SLI.
The idea of multi-GPU gaming is pretty simple on the surface. By adding another GPU into your gaming PC, the game and the driver are able to divide the workload of the game engine and send half of the work to one GPU and half to another, then combining that work on to your screen in the form of successive frames. This should make the average frame rate much higher, improve smoothness and just basically make the gaming experience better. However, implementation of multi-GPU technologies like NVIDIA SLI and AMD CrossFire are much more difficult than the simply explanation above. We have traveled many steps in this journey and while things have improved in several key areas, there is still plenty of work to be done in others.
As it turns out, support for GPUs beyond two seems to be one of those areas ready for improvement.
When the new NVIDIA GeForce GTX 980 launched last month my initial review of the product included performance results for GTX 980 cards running in a 2-Way SLI configuration, by far the most common derivative. As it happens though, another set of reference GeForce GTX 980 cards found there way to our office and of course we needed to explore the world of 3-Way and 4-Way SLI support and performance on the new Maxwell GPU.
The dirty secret for 3-Way and 4-Way SLI (and CrossFire for that matter) is that it just doesn't work as well or as smoothly as 2-Way configurations. Much more work is put into standard SLI setups as those are by far the most common and it doesn't help that optimizing for 3-4 GPUs is more complex. Some games will scale well, others will scale poorly; hell some even scale the other direction.
Let's see what the current state of high GPU count SLI is with the GeForce GTX 980 and whether or not you should consider purchasing more than one of these new flagship parts.
SLI Setup and Configuration
Running more than two graphics cards in your system requires a bit more planning than just running SLI. First, if you are targeting 4-Way configurations, and have the standard dual-slot graphics cards, you are going to be limited to a handful of motherboard and platforms that support it. There are Z97 motherboard available today that can run 4-Way SLI but they integrated a third-part PCI Express bridge chip to turn the x16 lanes of PCIe provided by Haswell and allow it to feed four different graphics cards at x8 bandwidth. Kind of like black magic.
By far the more popular platform for 3-Way and 4-Way GPU users is the Intel E-series of processors. Sandy Bridge-E, Ivy Bridge-E and now Haswell-E. These use the X79 or X99 (HSW-E) chipset and supply much more PCIe bandwidth from the processor, allowing native support for x8 PCI Express 3.0 in most cases. Our testing setup uses an Intel Core i7-3960X along with an ASUS X79 motherboard to support 4-Way SLI, both electrically and physically.
From a software point of view, setting up SLI is really easy, even for lots of GPUs. Once you plug in all the cards are you going to run, and then install the right driver (344.16 in our case), enabling SLI is as simple as selecting a radio button.
As long as you have the right SLI bridge connecting all of your cards (supplied with your SLI-ready motherboard) you are ready to go.
Testing Setup
If you have been following the graphics card and GPU reviews at PC Perspective for any length of time, you likely realize that we do our reviews quite differently. Rather than relying exclusively on something like FRAPs and an average or average + minimum frame rate, our testing process is quite a bit more complex. We capture the actual game footage coming out of the system and run some post-processing on the recording to measure frame rates as well as frame times. This allows us to measure real-world gaming experiences as well as show smoothness and frame time consistency in a far superior way as compared to other software based solutions.
Rather than paste in our entire process here, instead I will link you to our initial GeForce GTX 980 article and it's page that details the PC Perspective Frame Rating process. Give it a read if you are new to the site; it will make the coming pages make a lot more sense.
Test System Setup | |
CPU | Intel Core i7-3960X Sandy Bridge-E |
Motherboard | ASUS Rampage IV Extreme |
Memory | Corsair Dominator DDR3-1600 16GB |
Hard Drive | OCZ Agility 4 256GB SSD |
Sound Card | On-board |
Graphics Card | NVIDIA GeForce GTX 980 4GB |
Graphics Drivers | NVIDIA: 344.16 |
Power Supply | Corsair AX1200i |
Operating System | Windows 8 Pro x64 |
Our test system remains the same for this 3-Way and 4-Way SLI testing and because of the power efficiency of the GM204 GPU, we didn't have to worry about upgrading our 1200 watt power supply to a 1500 watt unit. In fact, as you'll see on the last page, we barely were able to hit over 800 watts in testing!
Some Thoughts On Scaling Measurement
An astute commenter on this story helped me realize that I had not explained the scaling measurements of the multiple GPUs and how the "optimal" scaling rates would look. In the following pages you'll see discussion of our performance results that mention specific scaling percentages. What is important to realize is that as you add GPUs to your system, the maximum (or optimal) scaling rate changes. For example, going from 1 card to 2 cards, your theoretical maximum performance scaling is 100%. When you go from 2 to the 3 cards though, that maximum is 50%.
Here is an example of how scaling would work in 4-Way SLI if everything worked perfectly. You are seeing performance of 14.7 FPS (Crysis 3 at 4K) with a single card, 29.4 FPS for two cards, etc.
When looked at from a step-by-step perspective, this how the optimal result looks. With a pair of GTX 980 cards you would love to see 100% scaling over a single card. The move to 3-Way SLI should result in 50% more performance when compared to the 2-Way SLI result. Finally, the move to 4-Way SLI should result in 33% additional performance.
On the following pages, when you see a scaling rate of 20% at the 4-Way SLI level, then you know that is actually decent scaling considering the maximum theoretical level.
It would be awesome to see
It would be awesome to see this run again with water blocks and see what the difference might be.
Overclocking the gpus is not
Overclocking the gpus is not going to change the scaling factor.
Maybe you didn’t get full
Maybe you didn’t get full utilization out of 4-way due to Maxwell asking for more power, there for limiting itself.
http://www.tomshardware.com/reviews/nvidia-geforce-gtx-980-970-maxwell,3941-11.html
If each card is capable of asking for 290watts then a 1200watt PSU will not be enough.
http://media.bestofmicro.com/J/E/454298/gallery/00-Power-Consumption-1-Millisecond_w_600.png
Should have tested with a 1500watt+ PSU see if that shows any performance increase.
I had a power supply runnig
I had a power supply runnig at 1200 watts, so I am sure this isn't a problem of power delivery.
But good link!
92% efficiency on a Corsair
92% efficiency on a Corsair AX1200i is 1104watts. If the GTX 980 are asking for 290watts x 4 a total of 1160watts. That leaves 40watts for the rest of the system.
I don’t think 40watts can be enough for the rest of the system when the i7 3690X idles at 99watts and during load uses 216watts ? That puts the system 1380watts just by CPU+GPUx4 alone well over 1200watts.
Power supplies do not work
Power supplies do not work that way. They’re rated for DC output wattage.
Firstly, 1200W is what the
Firstly, 1200W is what the PSU supplies to the system. Efficiency doesn’t affect the output wattage, it affects what the PSU draws from the wall.
eg. if it’s supplying 700W, the AX1200i has an efficiency of ~92% so it draws 700/0.92 = 760W from the wall.
eg2. if it’s supplying 1200W, the AX1200i has an efficiency of ~88% so it draws 1200/0.88 = 1360W from the wall.
Secondly, the 980 don’t run at a continuous 290W draw, it has occasional current spikes. If the average system draw is less than 700W, a 1200W power supply should have been perfectly fine to cover that sort of thing.
Just because the average is
Just because the average is low doesn’t mean the GPUs aren’t asking for more power.
If the load is held constant, then the lower power consumption measurements vanish immediately. There’s nothing for GPU Boost to adjust, since the highest possible voltage is needed continuously. Nvidia’s stated TDP becomes a distant dream. In fact, if you compare the GeForce GTX 980’s power consumption to an overclocked GeForce GTX Titan Black, there really aren’t any differences between them. This is further evidence supporting our assertion that the new graphics card’s increased efficiency is largely attributable to better load adjustment and matching.
Easy to see if you look through the graphs that its not on occasion its a constant dips and spikes which make up the misleading average. Maxwell just does it better (faster) then Kepler and AMDs PowerTune.
http://www.tomshardware.com/reviews/nvidia-geforce-gtx-980-970-maxwell,3941-12.html
Shut up, man. If you’re gonna
Shut up, man. If you’re gonna so anal, let me be a bit anal too: a 1200W PSU is capable of giving more than 1200W of PSU. Quite a bit more.
A 400W PSU can for example easily power a system that demands 500W, as the 400W is only what is advertised and sold on the product. It can actually go higher.
Shut up, man. If you’re gonna
Shut up, man. If you’re gonna so anal, let me be a bit anal too: a 1200W PSU is capable of giving more than 1200W of PSU. Quite a bit more.
A 400W PSU can for example easily power a system that demands 500W, as the 400W is only what is advertised and sold on the product. It can actually go higher.
They are right the figures
They are right the figures listed for power supplies are nominal figures.
Between 1990 and 1994 I was stationed in Germany. My barracks room was almost considered a day room for my floor. I had a dual NTSC/PAL 38″ TV (CRT type, flat screens came later), a Pioneer laser disk player, 4 VHS systems (1 Pal to NTSC, 1 Super VHS NTSC, 1 Pal/Secam/Mesecam), a super Beta, Fisher AM/FM/turntable/cassette stereo System, and two DBX boxs to route signals between equipment and the television. I also had an Amiga 500 computer. Because of the power cords only the television and the PAL/Secam/Mesecam VCR could be plugged directly into the wall. The rest used NEMA 5-R15 plugs. ALL the rest were plugged into power strips that finally ended up going into a 75W transformer. Almost 24×7 the computer was running, in the evenings friends would be watching television, which meant using at least 2 dbx and 1 or more video recorders. Friday evenings I would always record the German TV shows (soft porn) on the PAL VHS and then while watching something else I rented, I would be converting the German shows from PAL to NTSC format for friends to watch. I would easily be drawing 300-400W through that 75W transformer but it never blew a fuse.
Across the hall a friend would let me iron my uniforms. The irons would be plugged into a 1000W transformer. Check how much power draw for pressing cotton. It is close to 2000W. No problem with the transformer blowing.
While a power supply for a computer might not be as sturdy as those transformers, they are not fragile. They can usually 10-20% more power with no ill effects. Good ones are can take even more especially for short periods of time.
I have 4 of these monsters
I have 4 of these monsters and a 5960X plus two 6tb drives and 64Gb of ram, my Rosewill Hercules 1600W power supply works great. No bottle necks at full load when rendering 4K video.
That is ENTIRE SYSTEM power
That is ENTIRE SYSTEM power draw. GTX 980’s can only draw up to 125% of its 165w TDP which is 205w (unless you modify the video bios.
The GTX 980 is damn efficient and when overclocked to the highest aircooling OC (~1500mhz core, ~4000mhz mem) its as fast as 2 stock clocked GTX 770’s or 4 stock clocked GTX 480’s.
My 1 overclocked GTX 980 uses 120% TDP (198w) in furmark at 1505mhz core and 3985mhz memory. If you only game with 4 of these, you could use a minimum of an 800w PSU.
While gaming at this OC, I only reach about 173w/105% TDP and 4 way sli is hard to achieve 100% load like 1 or 2 cards can
If you had insufficient power
If you had insufficient power supply, wouldn’t the system crash rather than throttle?
Likely yes, though this isn’t
Likely yes, though this isn’t necessarily the case. It is just likely that the computer isn’t engineered in a way to prevent crashing on insufficient power.
Lets clear things up the
Lets clear things up the cards that were using 250watts were gigabyte windforce cards, those are not reference cards. Gigabyte is known to loosen up power constrains of the card. the ref card was well under 200watts.
Gigabyte windforce cards come with 2x8pin power connectors were as ref is 2x6pin.
Anything more then 2way SLI
Anything more then 2way SLI is a total waste for games.
SLI/crossfire in general blows.
Well I agree with first
Well I agree with first comment…
From what I have heard &
From what I have heard & read,Crossfire is still too choppy ,but my experience with 2-way SLI,have been incredible.I agree that 3& 4 way SLI for gaming ,though is not worth the price-performance gains .Strictly for e-peen status.
CF and SLI are about the same
CF and SLI are about the same in terms of microstutter and game compatability.
They’re both a very mixed bag and you shouldn’t bother with them unless you really want to game at 4K resolutions, have lots of extra cash lying around, and are willing to put up with a fair amount of driver oddness.
Actualy, 290-290X CFX is
Actualy, 290-290X CFX is better than the 7xx series SLI, at least in frame variance.
Wonder if there is a chance
Wonder if there is a chance for OpenCL/CUDA benchmarks? Like LuxMark/LuxBench, or Blender, or other CUDA/OpenCL?
Just curious if having 4 of these would be useful for this type of workload or if there is some bottleneck for these tasks also?
It depends on your code, but
It depends on your code, but most compute task are independent enough that you should see near linear scaling unless there is a communication limitation (not enough pci-e bandwidth between cpu and gpus).
Apparently it works quite
Apparently it works quite well:
http://cdn.eteknix.com/wp-content/uploads/2014/09/nvidia_gtx980_SLI_graphs_luxmark.png
Source: http://www.eteknix.com/testing-nvidias-geforce-gtx-980-4gb-graphics-cards-sli/13/
I’ve always wondered about
I’ve always wondered about why reviewers calculate the scaling percentage of multi-GPU set-ups the way they do.
I noticed that when calculating the scaling for 3-way and 4-way, those values are calculated against the previous value i.e. 3-way results compared to 2-way and 4-way results compared to 3-way. Isn’t that basically like saying 3-way performance must double that of 2-way or 4-way performance must double that of 3-way, when adding an additional GPU would just add the performance of a single GPU? It’s like asking for magic.
Think about it. 2-way’s performance is just the sum total of performance of 2 GPUs minus some driver and/or game code overhead. Wouldn’t mean that 3-way and 4-way’s performances are the sum total of 3 and 4 GPUs respectively?
Let’s use the Crysis 3 test as an example, a single GTX 980 has an average fps of 14.7 at 4K while on 2-way, that is bumped up by 13.5 fps for a total of 28.2 fps with a scaling of 92%. Now, going 3-way gets us up 39.4 fps which means we gained 11.2 fps from adding one more GPU. That 11.2 fps is 76% of the 14.7 fps we got from running a single GPU. Since we only added one GPU going from 2-way to 3-way, wouldn’t that mean the scaling of 3-way in this game be 76% instead of 40%? Using the same method to calculate, 4-way is 80% scaling which is even a better result than that of the 3-way one.
This is an interesting
This is an interesting idea…let me think on it for a bit.
No need to think, that way is
No need to think, that way is just a better way of calculating the fps gain!
We’re whipping up some charts
We're whipping up some charts to add to the piece – showing ideal vs. measured.
Yeah, I agree with tabuburn –
Yeah, I agree with tabuburn – it looks almost perfectly linear as you add cards in Crysis 3.
Why would we calculate it any
Why would we calculate it any differently !
Each GPU added would simply increase the number of Cores available, with the ‘inefficiency’ of them being located on different Cards.
Thus, in a perfect world of scaling, 2 GPUs would be twice as fast as 1 GPU, and 3 GPUs would be 3 times as fast as 1 GPU (etc.).
Why would we think that 3 GPUs should be 2 times as fast as 2 GPUs (etc.), that makes no sense; you would need 4 GPUs to calculate 2 times as fast as 2 GPUs.
This is why Benchmarks that scale well (like LuxMark, FAH etc.) are better than a Game that clearly does not scale well (and thus, it is apparent, that the Programmer was more concerned with simply getting the Code to run on one GPU than having the Code ‘behave nicely’ with multiple GPUs).
That always confused me as
That always confused me as well and you explained it well, thanks!
As a response to this
As a response to this comment, I have added a couple of sections to the review on the first and last pages, with some additional graphs to try and demonstrate what is being discussed.
Let me know what you think!
This has nothing to do with
This has nothing to do with the article but Nvidia is going to have a hard time dealing with newer games that are on xbox1/ps4 when they launch given the fact that Nvidia will not have optimized drivers for them.
AMD will have a advantage since the hardware in consoles is X86 arch and is under gcn so this gives AMD a natural optimization over Intel/Nvidia hardware.
Only way Nvidia will have a advantage for now on if it games are true Nvidia The way it’s meant to be played games. Shadow of mordor is not a true Nvidia game. It’s just published by WB and WB has a partnership with Nvidia so Nvidia got it’s name on it just for that reason. The next drivers for SOM, A I and Ryse SoR will be very very interesting and I think you should do a followup article on SOM when the new drivers hit to show performance of green team vs red team again.
Giving the performance as a
Giving the performance as a multiple seems like an easy way to understand how good the scaling is. Obviously, a 4-gpu set-up should have a maximum of 4x the performance. Getting ~3.5x is relatively good scaling at the moment. It still doesn’t seem to be worth it at all since most games have playable frame rates at 2-way SLI unless you are playing with a ridiculous display set-up.
Giving the performance as a
Giving the performance as a multiple seems like an easy way to understand how good the scaling is. Obviously, a 4-gpu set-up should have a maximum of 4x the performance. Getting ~3.5x is relatively good scaling at the moment. It still doesn’t seem to be worth it at all since most games have playable frame rates at 2-way SLI unless you are playing with a ridiculous display set-up.
This is what I came here to
This is what I came here to say. But tabuburn beat me to it.
The FPS of the first GPU is the 100%. So let’s suppose you have a perfect scaling scenario in an ideal world:
1 GPU = 30 FPS
2 GPU = 60 FPS
3 GPU = 90 FPS
4 GPU = 120 FPS
In this ideal scenario, each of these additional GPUs have 100% scaling because perfect scaling = 100% when counted relative to the FPS of the single GPU.
If you want to count perfect scaling relative to the previous SLI/Crossfire setup, then perfect scaling for 3-way is 50% (3 GPUs / 2 GPUs = 150%) and perfect scaling for 4-way is 33.3% (4/3 = 133.3%).
So for example, when you said Crysis 3 3-way SLI scaling is “only” 39%, it is important to note that if you’re calculating it the way you were, the perfect scaling would be 50%, not 100%. So 39% is actually pretty good as far as 3-way SLI scaling goes.
When you say 3-way scaling is “only 39%” and, apparently, thinking that the ideal 3-way scaling under that method of calculation is 100%, then you’re expecting the third GPU to have the performance of two GPUs put together, and the fourth GPU to have the performance of three GPUs put together, which doesn’t make sense:
1 GPU = 30 FPS
2 GPU = 60 FPS
3 GPU = 120 FPS
4 GPU = 240 FPS
nod nod
nod nod
Check that update referenced
Check that update referenced above. Should be clearly now; you are correct.
Sweet, thanks.
Also, please
Sweet, thanks.
Also, please note that I think the first method of calculation is more sound, and it gives better graphs with the data points from multiple game benchmarks more clearly displayed as the vertical spread for 3-way and 4-way is also 100% of the graph. That way the data points are spread out over a bigger vertical length and are overlapped less.
Additionally, and perhaps more importantly, it gives an easier and visual way of comparing scaling for a single game between 2-way and 3-way and 4-way setups.
The graph as it is now, we can easily visually compare scaling between two games. But if I want to quickly compare ~visually~ at a glance 2-way and 3-way scaling for a single game, say Crysis 3, then I can’t do that.
I was just thinking the same
I was just thinking the same thing when I read it, that I really don’t like the method of measuring scale between each step. It’s easier to understand benefit/cost of buying the cards by using basic multipliers. For example, Crysis 3 4K:
1 GPU = 100% = 1x
2 GPU = 192% = 1.9x
3 GPU = 268% = 2.7x
4 GPU = 348% = 3.5x faster for 4X the cost. Benefit/cost ratio of 0.88 overall (1.0 being perfect) doesn’t sound so bad, does it?
Again, Sniper 3 4K:
1 GPU = 100% = 1x
2 GPU = 187% = 1.9x
3 GPU = 280% = 2.8x
4 GPU = 360% = 3.6x faster for 4X the cost. Benefit/cost ratio of 0.90 overall (1.0 being perfect). Again, not bad at all!
If anything, using those examples, this tells me that 4-way SLI is worth it.
For those 2 games yes but not
For those 2 games yes but not for the 5 other games.
Battlefield 4
Bioshock Infinite
GRID
Metro: Last Light
Skyrim
“If anything, using those
“If anything, using those examples, this tells me that 4-way SLI is worth it.”
Why are you restating the obvious?
When doing cost/benefit you
When doing cost/benefit you have to consider everything and not just cherry pick the most favorable examples. Especially since in the real world PC gamer crowd most no one just plays those 2 games.
Seeing a lot of dropped
Seeing a lot of dropped frames there on the frame times plot, why aren’t they reflected in the observed fps chart which should be different to the fraps fps? What am I missing here?
Where exactly do you see
Where exactly do you see dropped frames? You are seeing a lot of frame time variance, but no DROPS that I can see.
Maybe I’m reading it wrong,
Maybe I’m reading it wrong, but when you look at say the bioshock frame times plot when the line goes down to zero multiple times, aren’t those dropped frames or runts?Aren’t those frames being counted even though they don’t show on screen at all?
My mistake, on closer
My mistake, on closer inspection there are slight differences in the observed fps vs fraps fps, I was expecting the difference to be a little more pronounced.plz ignore.
“Where exactly do you see
“Where exactly do you see dropped frames” statement is proof enough that you, Mr. Shrout, have an inability to understand graphs. You’ve probably got somebody doing these graphs and interpreting them for you, but he’s probably to busy kissing your a$$ then to actually tell you where the frames are dropping. You should fire him.
Second thing I would like to point out. I can’t believe there’s no Mathematician or Cal Tech Professor in the fields of Engineering, here to tell you that the concept of Percentile versus Frame Variance and Minimum Extreme FPS is a nice idea, but it’s wrong. You’re basically stating that Percentile is an Input to the function of that curve, and it produces an output in both “Min FPS” or “Frame Variance” graphs. This is why the Chinese are beating the Americans in Math, and you are showing proof of that. This is like building a 5 inch thick metal door that’s being displaced by pistons. You’re saying that the doors position in the X is independent to it’s position in the y, and this ideology is incorrect. Both X and Y in my example here is dependent on Time, and they teach this shit in Dynamics. I’m not sure if you got the idea to do this from FPS being inverted to Frame Time Variance, and said “shet son, lets run with it and see what people think” or you were told this was correct. If you want to be taken seriously, fix this because you won’t learn much from it, and it’s not correct. I would suggest inverting it. Make Min FPS and Frame Variance the Independent or the input of the graph, and make the Y or Output the Percentile. This way, you are stating that the percentile is dependent on the Frame Variance Data and Minimum FPS. Frame Variance and Min FPS are independent because it’s data that you collected from other results at some interval of time. Turn it into a bar graph and not a curve. Say at Domain Intervals (0,1.0FPS;mSxF^-1), we have Y1 amount of percentage. So at 0.0 to 0.1 mSxF^-1, the card appears to either drop frames or produces frames even faster by 0.8%. At 15 FPS in Game “Battlefield 4,” this frame rate occurs only 3% of the time while playing this PC Game.
mSxF^-1 = Time (mS) per Frame.
Failz
Failz
Why don’t you normalise the
Why don’t you normalise the scaling factors by multiplying the percentage you have calculated by the number of additional cards being used? This would give you a performance scaling as a percentage of the theoretical maximum, a much more useful metric.
For example if you had a linear performance increase and your calculated performance percentages for 2-way, 3-way and 4-way were 80%, 40% and 26.7% respectively then a layman may well believe that the going 3- or 4-way was not worth it, but the graph would show otherwise, normalising as I suggested would yield 80%, 80% and 80% resulting in the benefit being clear to all.
2 GTX 980’s $1100
3 GTX 970’s
2 GTX 980’s $1100
3 GTX 970’s $990
It sounds like you’d recommend 2 980’s even though drivers may improve over time.
I’m wondering what there is
I’m wondering what there is to recommend. The 970 looks like it uses even more power than the 980- and for what? ANY of these games will run fine on ONE board and you only have a widely accepted scaling benefit with two. Then you have to wonder if the human factors trade off with the power bill.
This is only for a very small percentage of people that have as much ego as money.
Less cards in SLI/CF
Less cards in SLI/CF eliminates any issues, As you get 3x SLI/CF the return gets less and less. As can see in some graph’s games tend not to be optimized for 3way+ SLI/CF completely. They can do stuff in drivers but better results can be done in game.
Some of your tests are not
Some of your tests are not good for good multi GPUs “scaling” test.
You should really check GPU usage.
metro redux, for example, which does work great for SLI (over non-redux version which was total crap) – it is hard locked at Tri-SLI. I will not use the 4th card at all.
Strange about the bf4. I have Quad gtx 980s (coming from quad titans).BF4 will max out all GPUs. 4 is faster than 3 for me. That said, single player can be wacky sometimes with GPU usage. Might i suggest the practice range (or multiplayer match by yourself).
Without me using Quad i’d not be after to play with ultra and high AA settings (at 4k). BF4 will totally break with some OSD, even to LCDs – but lucky have fancy frame capture stuff 🙂
(i’m playing a 32″ 4k titled screen).
4 cards might not be needed for most.. but min 3 is needed for 4k gaming. It isn’t about max fps or even avg.. it is about never dropping below 60. 🙂
yes, price/scaling for less that 4k is a bit wasteful (haha.. unless compared to people that ran multi Titans 🙂 )
These cards run cool.. use low power and hella OC well. 🙂
but if you are going 3-4 gtx 980 – go water. 🙂 The noise otherwise is painful.
(without SLI AND 4 cards one would not be able to play Shadow of Mordor maxed at 4k- SLI. The hacked in support isn’t great.. but that gets it to 70-80fps. 1-2 card is unplayabe at 4k.
crysis 3 isn’t that demanding 🙂 (2-3 cards at 4k is enough)
Don’t confuse SLI scaling and how well a game support SLI.
If a game can’t max out % usage that is the games problem not a function of SLI scaling. That said, if the game’s support for SLI is bad then an investment a multi GPUs isn’t a good one.
But monitoring GPU usage % is almost as important as the FPS if you want to talk about SLI scaling.
This test is worthless
This test is worthless without positing the CPU speed. A highly overclocked CPU is extremely important for 3-4 way SLI setups.
Stock 3960X processor.
Stock 3960X processor. Overclocking won’t make much difference, sorry.
Yup. Especially at high
Yup. Especially at high resolutions like 4K where you’re massively GPU bottlenecked.
Completely incorrect
Completely incorrect assumption. Did you even enable PCI-E 3.0 on the RIVE? 689 watts for a 4-way SLI system, barely 200 watts of power use more over 2-way SLI by adding two more cards.
Test methodology was in error. As for someone who has built and tested some of the fastest 4-Way SLI and crossfire setups in the world, your numbers don’t add up.
Completely incorrect
Completely incorrect assumption. Did you even enable PCI-E 3.0 on the RIVE? 689 watts for a 4-way SLI system, barely 200 watts of power use more over 2-way SLI by adding two more cards.
Test methodology was in error. As for someone who has built and tested some of the fastest 4-Way SLI and crossfire setups in the world, your numbers don’t add up.
PCI 3.0 doesn’t change the
PCI 3.0 doesn’t change the results (maybe 5fps). You won’t even notice it if it isn’t enabled.
PCI 3.0 doesn’t change the
PCI 3.0 doesn’t change the results (maybe 5fps). You won’t even notice it if it isn’t enabled.
Completely incorrect
Completely incorrect assumption. Did you even enable PCI-E 3.0 on the RIVE? 689 watts for a 4-way SLI system, barely 200 watts of power use more over 2-way SLI by adding two more cards.
Test methodology was in error. As for someone who has built and tested some of the fastest 4-Way SLI and crossfire setups in the world, your numbers don’t add up.
Nothing new, i have seen a
Nothing new, i have seen a guy use 4 wat sli plus a 5th identical card for physx black titans on evga forums, lmfao. Fyi it works.
Sounds like the PC gamer
Sounds like the PC gamer equivalent of one of those sound system audiophiles who spend $500 on a wooden knob or power cords from the wall to their receiver.
I’m curious how the ASUS
I’m curious how the ASUS P9X79 Deluxe can support 4-way SLI ?
If you check ASUS website it clearly states 3-way SLI
http://www.asus.com/us/Motherboards/P9X79_DELUXE/overview/
•3-Way SLI and Quad-GPU CrossFireX Support!
If you download the manual. On page 36 (2-14). It says the 3rd PCI-E is disabled if the 4th is occupied.
We use the Rampage IV
We use the Rampage IV Extreme.
Isn’t this logical scaling?
1
Isn’t this logical scaling?
1 to 2 card scales at 100% because you are doubling the card
2 to 3 cards doesn’t mean it will scale an additional 100%, it will be halved to 50% more on an ideal setup. because you’re referencing it from a 2nd setup
3 to 4 cards will far scale less because you’re comparing it with a 3-card setup. so expect the scaling to go down further 25% on an ideal scenario
maybe
2 to 4 cards will scale between 50% to 100% because you’re doubling the performance
Ryan
the GTX 980 tri-sli
Ryan
the GTX 980 tri-sli and quad-sli should have been compared with the competition. Tri-fire Radeon R9 295X2 with R9 290X and Quad fire Dual R9 295 X2. Anyway from your previous review its clear that Quad Fire is a beast at 4k when its well supported like in Crysis 3, BF4 and Tombraider. The problem is that game support is not consistent and that is the problem with CF and SLI. Still R9 295X2 with XDMA CF is a fantastic solution for 4K gaming.
https://pcper.com/reviews/Graphics-Cards/Radeon-R9-295X2-CrossFire-4K-Quad-Hawaii-GPU-Powerhouse/Battlefield-4
A big thanks to the readers
A big thanks to the readers and also to ryan and allyn for updating the article almost in “real time”. It clearly shows the cards are doing a decent job at scaling when properly used. Now the burden is on the game engines to actually handle scaling properly and as we can see from the graphs some of them are not ready yet. I wonder if crossfire behave exactly the same now.
Now, that you’ve done the fun
Now, that you’ve done the fun useless comparison, how about some useful ones:
2 x 970 vs 1 x 980
or
3 x 970 vs 2 x 980
What is the fps/$ in those cases?
now that you have made a
now that you have made a uselessly condescending comment, we can make a simple supposition.
they are both the same generation nvidia GPU’s so scaling should be the same
google: sli gtx 970
boom
techpowerup article, time to compare crysis 3. yep scaling is the same. 11.2 fps goes to 22 fps
http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_970_SLI/9.html
http://imgur.com/gallery/C5envvd
Your comment is the only
Your comment is the only condescending one.
Get off the Internet and go get laid.
The whole point of visiting sites like this one is so I won’t need to assume anything and just see relevant benchmark results.
No need to start getting
No need to start getting personal here. I think he just misunderstood the ‘fun “useless” comparison’ part. He took it as if you were negatively critizing the author in a troll-way.
Had to read it twice myself.
I think the scalling is
I think the scalling is affected by the CPU bottleneck due to stock clocks of the CPU. i would like to see this kind of multi GPU review
performed on overclocked system with good clocks on the CPU and memory.
I have to love that you guys
I have to love that you guys blame the SLI profile immediately when you’re clearly CPU bottlenecked.
Here you have admited it;
“Our power testing was taken from Crysis 3; we obviously had to pick a game that had good scaling up through the 4-Way SLI results in order to make sure each GPU was being utilized as much as possible.”
Wait, GPU loads weren’t maximized in any other game, lets take Bioshock where was no advantage at all from a 3rd/4th card? That’s a CPU bottleneck, end of it. What were the GPU loads? I assume in single mode the GPU was at 99%, since theres a double gain so again 99%/99% in 2Way SLI, since you didn’t take any advantage of a 3rd that should be 66%/66%/66% in 3 Way SLI, and 33%/33%/33%/33% in 4Way SLI.
Get each GPU at maximum load, not 30%, let’s not blame the drivers when our CPU was holding us back, that’s illogical. Tell us the CPU was limiting us, if you still had bad scaling from 2 way sli all the way up to 4 Way SLI and the GPU loads were all max’ed out go ahead blame the drivers.
I’ll give an example (1080p ultra settings/780/3930K);
– Single GPU at 50% load with 55 fps: http://i.imgur.com/vJkPwDv.png
– 2 GPU’s at 25%/25% load with 55 fps:http://i.imgur.com/HEqn7kv.png
That’s not because SLI scales bad, thats because that spot is quite CPU intensive where my CPU bottleneck is extreme, whenever I move somewhere else and remove the FPS cap the GPU’s all crank up to 99%/99% load with nearly a lineair FPS scaling between 1 and 2 cards.
A 3960x (no clock mentioned so I assume at stock) isn’t an excuse, all CPU’s bottleneck to some point and these days its mostly seen in SLI setups.
Leaving an article about SLI scaling a moderator on the geforce forums wrote what could cause SLI scaling and explained pretty much what I’ve been saying: https://forums.geforce.com/default/topic/532913/sli/geforce-sli-technology-an-introductory-guide/post/3749687/#3749687
I’ve seen some people comment
I’ve seen some people comment on this already and I am familiar with the concept of diminishing returns, which appears to be the argument about adding a card in SLI, but in your conclusion I still find fault in the statement below:
“Those two games showed expected scaling rates of 90%, 39% and 29% as you go up the multi-GPU ladder. That means for a second investment of $550 (the cost of another GTX 980) you will get
90% added performance
. Another $550 investment nets you
another 39%
, while a fourth payment of $550 only gets you
29% more
.”
The problem that I and others seem to have with this statement is that it implies that when you sequentially step up the “GPU ladder”, your reference point must change to the ladder step before it. Instead of consistently comparing each additional to the original position, you are changing your comparison each step up.
The first GPU gives you a reference point of 100% performance. The second GPU then gives you 90% of that amount of performance, on top of the first 100%. If you add the third, your calculation would imply you only gain 39% of that original amount on top of that 190%, but in reality, you gain an
additional 78%
on top of the 90% from the second card, which adds up to 168% improvement over the single card reference point. With the 4th card, then, in this example at least, you have an 87% increase, which puts you at a 255% improvement over a single card, and 355% of the performance.
obviously my html did not
obviously my html did not come out right…
Well HTML tags didnt work.
Well HTML tags didnt work.
The default measurement that
The default measurement that Ryan and other sites use is the performance gain by going 1 more. Most people are going to want to now the benefit of each additional $550. If a change is small compared to the previous set up in game experience, as a player, that is the meaningful measure.