2 lesser GPUs vs 1 better?

[BD231]

If you have to keep your frametimes high above your monitor's refresh rate so that you don't notice microstutter, that defeats the purpose of going dual GPU, doesn't it?

Like I said, people get sucked into the marketing and only look at the FPS counter, which doesn't tell the whole story. Because of microstutter, you're only getting a small fraction of return on the huge investment of a second card. It's very simple to understand this concept if you look at individual frame times. Let's say you have a single GPU capable of running a game at 30FPS. Let's say it also has great drivers with perfect scaling (lol) and you can add in a second GPU to get 100% more performance. The FPS counter will say 60FPS, but the frametimes will tell a different story. At 30FPS, each from is rendered on average every 33.3ms. Note that even on a single GPU, there will be irregularities as the scene changes, but they are very small deviations. With the two GPU's at 60FPS, you'll see an average frame time of 16.7ms, but the actual frame times vary much more greatly. Generally there's a sort of stacatto type patter where an odd frame is rendered followed closely by the even frame, then a longer period before repeating. So within the average frame time of 33.3ms for two frames (2x 16.7ms), frame 2 is rendered after frame 1 in 10ms, then there's a 23.3ms wait. That wait gives us the phenomenon of microstuttering, so now you're actually only getting 1000/23.3ms = 42.9 FPS.

Therefore, even though a benchmark or an FPS counter will tell you you're getting 60FPS and double the performance, the game plays and feels no differently than if you were playing on a single GPU at ~43FPS. That's why multi-GPU is a poor return on investment and should only be entertained when there are no other options left on the table to increase performance.

Now I should also add that you can minimize microstuttering by adding more GPU's into a multi-GPU array. Even Tri-Fire or Tri-SLI will do a lot to break up that "lag" period scene in dual-GPU configurations. But, that adds more driver problems, scaling issues, and overhead, in addition to cost, noise, heat, etc. There's a great video out there using HL2 and a high speed camera that show that "stacatto" rendering due to microstutter, but for the life of me I can't find it atm.

I don't get sucked into marketing I run those types off, I had a genuine performance issue and I rectified it with a second card otherwise I wouldn't have opted. My monitor can't display more than 60 fps which I was well aware of when I bought the second card so right now anything above 60 fps is just ensuring I don't have the issue. In this case going dual GPU enabled me to go from only being able to play Witcher two at 1280x1024 to smooth sailing at 19x12 (native res) which a single GTX 460 just can't pull off, so in my case the benefits are huge because what I don't see going on in the background is doing nothing but helping my situation. I don't care about the other frames as long as I see a smooth picture so if that extra horepower gives me the frames I need yeah I'm going to give credit where it's due. A lot of the time I'm getting almost triple the performance of a single card.

Like your article points out not every game behaves the same way, I also don't understand why you'd think games made to be playable on modern single cards wouldn't play somewhat similar to someone getting more frames via a second card, especially when typical monitor refresh rates are pretty low, but in cases where you actually need the GPU power because the first just isn't cutting it an added card proves plenty useful which debunks your lack of purpose theory. If you truly believe frame counters lie that's on you, for me the results don't. I paid $260 bucks for my cards in total, that's almost half a 580 and I get most, if not all the benefits so sorry bro, not with you on this one that's all.

 

[Grooveriding]

I think it depends on the performance difference between the two setups. If you are comparing 560SLI to a 580, a 580 is better imo because of the single GPU experience and the extra raw frames 560SLI would give is not worth it.

I only recommend multi GPU for situations where no single gpu will give you a playable experience. Of course that said you can get more FPS on paper from multi-gpu for a lower cost than you would from one faster card.

The way I do it, is if there is a single GPU card on the market that is fast enough to run everything at my resolution the way I want it to run, that is the card I'll get regardless of price. If there isn't, then I'll look at multi-gpu.

 

[boxleitnerb]

Now I should also add that you can minimize microstuttering by adding more GPU's into a multi-GPU array. Even Tri-Fire or Tri-SLI will do a lot to break up that "lag" period scene in dual-GPU configurations

Do you have some more information about this? And maybe some frametime measurements comparing 2 and 3 GPUs? I only know the THG article, but I don't trust it because they probably had a (partial) CPU bottleneck with 3 GPUs (the less than perfect scaling points in that direction). Then it is only logical that you get less microstutter or none at all.

 

[exar333]

I think it depends on the performance difference between the two setups. If you are comparing 560SLI to a 580, a 580 is better imo because of the single GPU experience and the extra raw frames 560SLI would give is not worth it.

I only recommend multi GPU for situations where no single gpu will give you a playable experience. Of course that said you can get more FPS on paper from multi-gpu for a lower cost than you would from one faster card.

The way I do it, is if there is a single GPU card on the market that is fast enough to run everything at my resolution the way I want it to run, that is the card I'll get regardless of price. If there isn't, then I'll look at multi-gpu.

This. Get the best single-GPU you can afford, that will run what you need. If it cannot run what you need, get more (x2, x3, x4). If you cannot afford the one, then re-think your needs or display setup.

 

[Tempered81]

Here you can see microstutter in action (start video at 1:02)

http://youtu.be/zOtre2f4qZs?hd=1&t=1m2s

 

[MrK6]

I don't get sucked into marketing I run those types off, I had a genuine performance issue and I rectified it with a second card otherwise I wouldn't have opted. My monitor can't display more than 60 fps which I was well aware of when I bought the second card so right now anything above 60 fps is just ensuring I don't have the issue. In this case going dual GPU enabled me to go from only being able to play Witcher two at 1280x1024 to smooth sailing at 19x12 (native res) which a single GTX 460 just can't pull off, so in my case the benefits are huge because what I don't see going on in the background is doing nothing but helping my situation. I don't care about the other frames as long as I see a smooth picture so if that extra horepower gives me the frames I need yeah I'm going to give credit where it's due. A lot of the time I'm getting almost triple the performance of a single card.

No you're not, that's an absolute fallacy. The most you could get in a perfect scaling scenario is 100%. Realistically, the performance benefit is much less than that, as I demonstrated above. This is why I say people fall for the marketing.

Like your article points out not every game behaves the same way, I also don't understand why you'd think games made to be playable on modern single cards wouldn't play somewhat similar to someone getting more frames via a second card, especially when typical monitor refresh rates are pretty low, but in cases where you actually need the GPU power because the first just isn't cutting it an added card proves plenty useful which debunks your lack of purpose theory. If you truly believe frame counters lie that's on you, for me the results don't. I paid $260 bucks for my cards in total, that's almost half a 580 and I get most, if not all the benefits so sorry bro, not with you on this one that's all.

The GTX 580 is very overpriced for what it is, and there are better single GPU options available that would give your SLI configuration a run for its money in price/performance, never mind efficiency and features, such as an unlocked + overclocked 6950 2GB or a GTX 570. Not every scenario is perfect and sometimes the market will give more weight to one setup or the other. The point of my post was to highlight how inefficient multi-GPU is and the fact that you're not getting anywhere near the performance you think you are. Don't believe me? We can start benchmarking and I can show you personally.

I think it depends on the performance difference between the two setups. If you are comparing 560SLI to a 580, a 580 is better imo because of the single GPU experience and the extra raw frames 560SLI would give is not worth it.

I only recommend multi GPU for situations where no single gpu will give you a playable experience. Of course that said you can get more FPS on paper from multi-gpu for a lower cost than you would from one faster card.

The way I do it, is if there is a single GPU card on the market that is fast enough to run everything at my resolution the way I want it to run, that is the card I'll get regardless of price. If there isn't, then I'll look at multi-gpu.

I agree, although with the exception that I still weigh price/performance heavily. For instance, I stuck with my unlocked 6950 2GB instead of going with a GTX 580 simply because I didn't feel the ~20% extra performance was worth another $250.

Do you have some more information about this? And maybe some frametime measurements comparing 2 and 3 GPUs? I only know the THG article, but I don't trust it because they probably had a (partial) CPU bottleneck with 3 GPUs (the less than perfect scaling points in that direction). Then it is only logical that you get less microstutter or none at all.

I can certainly look for it. While the THG article is flawed inherently because it's not measuring frametimes, it shows some details. I don't think you can measure NVIDIA performance properly in their method since their cards employ a frame-meter rather than give direct data, I forget exactly how it works, but looking at the AMD cards you can see the improvement going to Tri-CF. CPU-bottlenecking could be an issue, so I'll see if someone else has done an article on it. In the meantime, I found the video I spoke of earlier that shows microstuttering in action using a highspeed camera: http://www.youtube.com/watch?v=zOtre2f4qZs

 

[gmaster456]

Minus a 1 or 2 exceptions, I will always prefer one single card vs two.

 

[jpeyton]

Single card for simplicity, but my 2 6870s outperform a single 6970 and cost me 30% less.

 

[gramboh]

Interesting video. I've been considering GTX560Ti SLI vs. selling my card and getting 7950/Kepler (in April), going to have to do some more research, that video clearly shows the effect though.

 

[Charlie98]

I myself prefer a single good GPU over 2 'OK' GPUs. 2 good GPUs (or better) are really needed for very high res displays. That said, sometimes a little less GPU power, but more memory, can help more in high resolutions. 1 single GPU with 3GB memory could be better in some situations than 2 GPUs equaling 110% of that performance, but with only 1GB.

Using my example of 2x 550ti's vs 1x 560ti... that would be 2GB memory vs 1GB memory. In the dual card setup, you wind up with the same amount of cores and twice as much memory as a single card.

 

[Charlie98]

In the meantime, I found the video I spoke of earlier that shows microstuttering in action using a highspeed camera: http://www.youtube.com/watch?v=zOtre2f4qZs

AH! Now I understand microstutter on M-GPU setups.

 

[dust]

Using my example of 2x 550ti's vs 1x 560ti... that would be 2GB memory vs 1GB memory. In the dual card setup, you wind up with the same amount of cores and twice as much memory as a single card.

Nope.

 

[Charlie98]

Nope.

Care to elaborate? Not being a smarty pants, I just don't understand the differences... :\

Would not 2x 1GB cards working SLI act as 2GB?

 

[dust]

Unfortunately no! You'd only be able to use effectively the memory of one card.

Also, if you have two cards with different amounts of memory, you'll get the lowest Vram size to consider for the couple of them.

 

[BD231]

All good points mr 6, I still believe there's plenty of value in the cheaper sli route despite its flaws.

 

[BallaTheFeared]

People don't spend $3000+ on screens and another $2000 on gpu's because MS is common.

Anyone trying to tell you otherwise has a secret agenda.

OP I wouldn't get the same core count in SLI for more than what I could get in a single card. Generally people like myself buy two 470s with 448 cuda cores for $150 each instead of getting 512 with a GTX 580 for $500. So for $300 I got 896 cuda cores instead of just 512 for $500. In this case it actually make sense, however 550ti sli vs 560ti makes none.

 

[TahoeDust]

To me, xfire/sli makes sense when it outperforms any single GPU on the market...and is cheaper. I went 2x6950s (unlocked) over the 7970. I got my cards for $150 less than the 7970 and they are faster. I have had no issues with microstutter yet.

 

[fffblackmage]

Care to elaborate? Not being a smarty pants, I just don't understand the differences... :\

Would not 2x 1GB cards working SLI act as 2GB?

It's like RAID1. The data in the first video card's vram is the exact data you'll find in the second video card's vram.

 

[PrincessFrosty]

People have already mentioned microstutter, it's been demonstrated in both Nvidia and AMD multi-gpu solutions, there's a good tomshardware article covering it in depth.

For many gamers the advantages of multi-GPU especially with AMD is mitigated somewhat because of this problem, I read quite a lot of people say that 60fps with multi-GPU doesn't feel like 60fps by a single GPU, I'd tend to agree with them having used all combinations over the years from both camps (SLI, Crossfire and single GPUs from both)

My advice is don't use 2 GPUs when you can use 1, if your requirements can be met by a single GPU then buy that, if there is no single GPU fast enough to handle what you need then go multi-GPU and at this stage I'd recommend Nvidia since their support seems better (right now) and have demonstrably less micro-stuttering.

Not being bias here, I've come from a 5970 and prior to that 2x 4870s in crossfire, now running a GTX580 and can say it's simply better than the 5970 despite the 5970 often getting faster frame rates.

 

[Charlie98]

It's like RAID1. The data in the first video card's vram is the exact data you'll find in the second video card's vram.

Gotcha... makes sense. I didn't know if it split the memory load between the two memory banks, but the RAID1 example makes sense.

...however 550ti sli vs 560ti makes none.

I was trying to keep as close to apples vs apples as I could for the purpose of my question. From what I gather, in this case anyway, the simplicity of one card beats any small gains possible with two. Maybe a better 'question' would have been 2x 560ti's vs a single 570 or even 580.

 

[BallaTheFeared]

Maybe a better 'question' would have been 2x 560ti's vs a single 570 or even 580.

Yeah in that case, if you were looking at 1GB cards or even 2GB 560ti's they'd be less than the cost of a single 580 while providing more performance. However 1GB is getting close to obsolete even at 1080p with dual gpu setups.

There are a few downsides there though...

First off, you're already maxed out with two cards, no tri or quad So you have no upgrade path from SLI'ing two 560ti's.

Secondly, most people would rather get a higher end card, like say the 570, then later on SLI it once they have the money.

There are pros and cons for each option, performance wise the 560ti's offer better performance for less. However you could always add a second higher end card later on, or in this case, two more, or even three more with 580s (unrealistic but point of fact).

 

[WMD]

I would say going the SLI/CF route is always better for performance/price. 2x6870 will equal a 7970 at almost half the price.

Drivers have improved to a point where micro stutter and poor scaling are non issues. 99% of all newer games scales perfectly on 2 gpu. The rest that does not scale can easily maxed out one one card.

 

[boxleitnerb]

Drivers have not fixed microstutter. They can mitigate the effects a bit, but the problem is inherent to the technology. So far, nothing can be done against it. As for scaling and issues, AMD has shown often enough that their CF-support is lacking.
I would much less hesitate to go SLI instead of one larger card than CF.

 

[WMD]

Drivers have not fixed microstutter. They can mitigate the effects a bit, but the problem is inherent to the technology. So far, nothing can be done against it. As for scaling and issues, AMD has shown often enough that their CF-support is lacking.
I would much less hesitate to go SLI instead of one larger card than CF.

Not completely but they improved alot. I have seen MS with 4870X2 but not with any of the newer gpus unless the framerate is below 60fps. Any remaining MS can be eliminated with a frame rate limiter with only drawback being slightly lower average fps. CF issues are usually fixed a few days after game release.

 

[zod96]

I have 2 560ti 2GB cards. I have no micro stuttering at all. I can now play BF3 at 1920x1200 with everything set to Ultra and my frames never go below 60. The downside is, my cards get hot and loud. I would have gone with a single card if I could play with the same settings as my 2 560's but at the moment their is no single card that can match the performance I am getting with these 2 cards. I did have a 580 and that was almost as good. But it would drop the frames into the mid 40's. I have heard that the new 7970 can match my 2 cards, but I'm not sure about that. I only paid about $450 for my 2 cards. 1 580 is about $500 and 1 7970 is about $600 so its up to you...