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Micro-Stuttering And GPU Scaling In CrossFire And SLI

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  • GPUs
  • Crossfire
  • SLI
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Anonymous
August 22, 2011 4:00:03 AM

We've received many emails from readers asking about the phenomenon known as micro-stuttering and what it means to multi-GPU setups in CrossFire and SLI. After running plenty of benchmarks, we're ready to weigh in on what turns out to be a real issue.

Micro-Stuttering And GPU Scaling In CrossFire And SLI : Read more

More about : micro stuttering gpu scaling crossfire sli

August 22, 2011 5:16:07 AM

This is a very interesting article, I have wondered about this issue myself many times in the past. I was always curious why I would see strange lag like anomalies while still achieving perfect frame rate. Bravo Toms
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9
August 22, 2011 5:24:47 AM

Well, I'm a little surprised that three cards in Crossfire seem to eliminate visible microstuttering -- I would have guessed that triple cards would increase stuttering. But it also seems like there must be other factors at work. Unfortunately, there really isn't a good way to test for other factor -- if you even could know what to test for. In some circumstances, it seems like my monitor is causing some issues. If I play a game (lets use Fallout New Vegas for example) at a Synced 60FPS, you can look at FPS and it never deviates. It only uses 1/3 of my GPU cycles. But on one monitor, at the same resolution, it micro stutters. On another monitor, it looks perfectly fine. I thought it was some lag variance -- but then I've been told lag is always constant, that the reason lag varies in monitor testing is improper test methods. What ever the reason, it's actually really annoying. And I'm not anything approaching a competitive FPS player. Thanks for helping to track this issue down.



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11
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August 22, 2011 5:37:51 AM

so will you now change your best gpu for the money from 2 x 6850's, since they obviously suck. I already bought one 6850 thinking it would be great to crossfire later and that was the best choice according to you toms........now i will have to throw it in the bin come upgrade time and buy a better single card. Oh, and AMD/Nvidia, if you cant get dual card configs to work properly, don't offer them, your wasting our money. Please fix this microstuttering crap, im sure it would be possible with a driver tweak.
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-10
August 22, 2011 5:40:28 AM

What happens with Vsync turned on?
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28
August 22, 2011 7:00:46 AM

why wasn't hybrid crossfire mentioned in this article?
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6
August 22, 2011 7:20:13 AM

i think the MSI Radeon 6870 Hawk is the best graphics card on the market right now in terms of heat, power, performance and price
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-9
August 22, 2011 7:47:26 AM

in most games you can limit maximum frame rates. So maybe if you limit max FR to let say 10 to 15 above min FR then the Micro-Stuttering effect would be gone ? anyone tried this? please share
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8
August 22, 2011 7:55:53 AM

What is performance like using other load-balancing methods, like the split frame rendering that SLI originally used, or ATI's Scissor mode? Are these modes still available to those that choose them?

Obviously, they won't reach frame rates as high as those attained through AFR, but if the frame rate loss is small enough, those modes might still be justifiable if they eliminate micro-stuttering altogether.

I'd be curious if these alternate methods could justify the cost of an additional card through added performance without coming with the drawback of micro-stuttering.
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13
August 22, 2011 8:11:45 AM

Regarding the decreased stuttering with 3 or 4 cards: could this be a similar effect to superimposing sine waves? Two waves a half cycle apart show visible peaks and valleys, while three waves at evenly staggered cycles form a much smoother band (on a graph or a scope).
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7
August 22, 2011 8:18:37 AM

I ma confused ... you are using 2 identical cards, so the frame rendering times as show on the metro 2033 second would be THE SAME on a single card as on a dual card configuration. the only difference is when each card starts to render right ?
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-1
August 22, 2011 8:18:48 AM

Good question 1kbuild
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5
August 22, 2011 8:18:51 AM

Could a frame be analyzed and split into certain pieces for each GPU to process? It would make each frame much more consistent if the load for each GPU was just about equal per frame even if there was overhead for splitting the load up and then having to transfer it to the first cards buffer.
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0
August 22, 2011 8:47:42 AM

Disable ULPS you noobs.
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-3
August 22, 2011 8:50:21 AM

I guess buying 3dfx was the way to go for Nvidia. If all midrange cards are equipped with only one link then I assume that we won't get to see exotic combinations of 3, 4 cards in the next SBM.
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-2
August 22, 2011 9:38:34 AM

Nice article, it was very usefull. BUT why Three-Way, and Quad SLI configurations aren't benchmarked ?
AND i saw that Lucidlogix makes things worse on Radeon HD 6870 X2, what about the Lucidlocix Virtu, integrated in many motherboards, does it affects performance of your graphics card, and if it does how?
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-3
August 22, 2011 10:55:19 AM

Page 9, first Ungine Sanctuary set of results, the 590 is displayed using AMD Crossfire colours.
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-2
August 22, 2011 11:08:31 AM

One reason single-GPU Nvidia boards may trail AMD boards in Mafia II is because Mafia II supports PhysX. With PhysX enabled, a single board can sometimes struggle.

Based on the summary conclusion, does this mean Tom's has firmly gone back to recommending that users purchase "the most powerful single-GPU board you can afford" again?
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2
August 22, 2011 11:34:29 AM

shoelessinsightWhat is performance like using other load-balancing methods, like the split frame rendering that SLI originally used, or ATI's Scissor mode? Are these modes still available to those that choose them?Obviously, they won't reach frame rates as high as those attained through AFR, but if the frame rate loss is small enough, those modes might still be justifiable if they eliminate micro-stuttering altogether.I'd be curious if these alternate methods could justify the cost of an additional card through added performance without coming with the drawback of micro-stuttering.


SFR was really good back in the day and it was enjoyable as well stable. Also it scaled well for two way setups but Nvidia killed it off because of quad and tri was becoming popular back in 08. ATI has other rendering modes as well such as tile but they went the afr rout as well. The best days of sli and crossfire are over but one can still try to optimize their way out of some micro shuttering.
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0
August 22, 2011 12:30:32 PM

One of the members of XtremeSystems has come up with a program that analyses the amount of variance from the average framerate from a fraps frame time file. Have a look at http://www.xtremesystems.org/forums/showthread.php?2584... for a link and some details on how to use it and results.

Toms could adopt this tool and use it to show the amount of MicroStutter along with their benchmark results. Many other sites like to show minimum fps in their graphs and I think showing the bottom 5% of frame times would be another way to show this problem up and compare the cards in your reviews.
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4
August 22, 2011 1:10:34 PM

A great article, but of course a few stickler points:
-It's not about Bulldozer
-I would like to read some more detailed observations of problems you were seeing with crashing and driver issues
-A suggestion in the conclusion about what YOU would do with your own setups, as many of us want to know what the pros think
-It's not about Bulldozer
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-7
August 22, 2011 1:45:03 PM

So based on the graphs at page 4, crossfire setups will still gain a performance increase but would suffer from minimum framerates similar to a single card?
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-1
August 22, 2011 2:19:39 PM

@jonbla
- the line related with a single card is very even (not big fluctuations) that means that the experience is fluid.
- in crossfire you see huge drops of frames and where it happens its not the minimum frame rate which is important but the fact that it related with delays in showing the frames.

To be more explicit: we have 50 frames per second; this is fluid only if they are distributed evenly within 1 second; but if you have 49 frames within 40 milliseconds and than the 50th frame at 1 second you will experience an annoying visual delay
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7
August 22, 2011 2:19:53 PM

@jonbla
- the line related with a single card is very even (not big fluctuations) that means that the experience is fluid.
- in crossfire you see huge drops of frames and where it happens its not the minimum frame rate which is important but the fact that it related with delays in showing the frames.

To be more explicit: we have 50 frames per second; this is fluid only if they are distributed evenly within 1 second; but if you have 49 frames within 40 milliseconds and than the 50th frame at 1 second you will experience an annoying visual delay
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-8
August 22, 2011 2:47:28 PM

really informative article. this has been my experience with micro-stuttering (if what i'm about to describe is the same thing):

Hardware: Single Geforce 9600GT + CRT monitor @ 1024x768.

Well, first thing that comes to mind is Halo 1. Obviously, it runs smooth as ...well just about anything that's very smooth :p . Point is, while playing sidewinder (empty game, lan hosting) and firing from a ghost, i observed some stuttering while approaching the part where the shade sits (i'm assuming everyone's played halo or seen RvB). I checked the fps graph built into Halo. Turns out that the fps jumps to 120+ from 85 (vsync: on) when i fire. That shouldn't happen (since i have vsync on) but it just does.

Second example is america's army 2. Was playing offline on Border (was testing anti-aliasing and other things). As most of you probably know, AA2 is very CPU intensive and runs mostly on a single thread. I had set the "Maximum pre-rendered frames" option to 5 (default 3) in the nvidia control panel. At 85 fps (vsync), the game was stuttering, couldn't see the fps fall below 80 though, but then again i didn't log it or anything, change in the fps may have been too fast to notice. changed the pre-rendered frames back to 3 and it was fine.

Summary: I wonder if the game code also introduces stuttering? Can the CPU or RAM be any sort of bottleneck?

p.s. Like someone else asked, if a dual card config is producing a min fps of say 100 with micro-stuttering, and if it's capped at 85 or 60 fps (through vsync), will the stuttering remain?
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-3
August 22, 2011 3:06:15 PM

what they need to do now is develop a more efficient cooling...maybe a peltier cooling option....i am sure that it can be done...liquid and air cooling suck big time...my water pump just started leaking on me the other day, good thing i had the pump on the bottom of the case and no parts were harmed....thank goodness for thermal shutdown option.
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-7
August 22, 2011 3:08:34 PM

I think you have stumbled on AMD's work on 6870 crossfire with their new bulldozer graphics part. I say this because its very unlikely the micro stuttering would have worked so well without AMD focusing on a quasi 3 way 6870 setup.
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-3
August 22, 2011 3:21:39 PM

Guess I should have stated next years Trinity and Komodo 2-8 core bulldozers.
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-3
August 22, 2011 3:33:18 PM

this article is a fail

micro stuttering is not a drop in FPS then go back to very

the thing your talking about in this article is LAG not micro stuttering



micro stuttering is a very rapid jerky movement on the screen

i personally have micro stuttering on Dirt 3 on my GTX 460 768MB(single GPU)


to give you a clue what micro stuttering looks like, have a look at this video at 2:39 http://www.youtube.com/watch?v=CHPtbDz7xgE
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-8
August 22, 2011 5:07:07 PM

I never had MicroStutter, wtf is that?
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-6
August 22, 2011 5:07:25 PM

oh yeah , and what about Bulldozer? :p 
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-7
August 22, 2011 5:10:28 PM

If some people do experience it, problem can be fixed with 120Hz refresh rate.
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-9
August 22, 2011 5:13:40 PM

Meaning either play games on CRT or on new LCD 120Hz. Whoever came up with LCD 60Hz and thought it is a good idea to use it for gaming was an idiot.
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-9
August 22, 2011 5:16:42 PM

I've owned 2 4870s for about 2 years. During those years, I haven't been able to play a single game with crossfire, gaining any FPS. The first game that actually seemed compatable was Crysis 2, which had bloom problems on certain levels. I messed with the settings, but nothing stopped it. I went to a single card, and not only did that effect go away, but my framerate was way better... Disappoint.
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0
August 22, 2011 5:16:58 PM

lradunovic77If some people do experience it, problem can be fixed with 120Hz refresh rate.


you should be careful on giving advices


manually setting your monitor to a much higher refresh rate could permanently damaged your monitor(as i experienced on my old CRT monitor)



fyi, i am using a 120hz monitor "Viewsonic VX2268wm" and i am using 1680x1050 @120hz on gaming and the micro-stuttering is still very apparent


same as my Dell 2007WFP S-IPS 60Hz monitor
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1
August 22, 2011 5:23:24 PM

you did not specify that people need a 120hz monitor

lradunovic77If some people do experience it, problem can be fixed with 120Hz refresh rate.



people on the internet has very high IQ so i wont be surprise if someone is raging because he broke his monitor


and to clarify

120Hz monitor DOES NOT SOLVE micro-stuttering
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6
August 22, 2011 5:27:23 PM

My second post after

120Hz monitor DOES NOT SOLVE micro-stuttering

was

Meaning either play games on CRT or on new LCD 120Hz. Whoever came up with LCD 60Hz and thought it is a good idea to use it for gaming was an idiot.




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-6
August 22, 2011 5:29:21 PM

As I said even if someone tried to change refresh rate it wont be possible cause there not even an option to do so.
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-6
August 22, 2011 5:30:43 PM

Great article!
I have been messing with SLI for years and have never gotten an acceptable experience. I often said the game does not play right but I could not describe it. Friends with similar systems to mine always said they were very happy with their SLI setups. I thought it was an issue with my mother board or something, now I think some people might just notice it more.
A few years back I built a Q6600 with 2x 8800gts in SLI. Although the frame rates with 2 cards went up I did not like it and could not explain it. Later I rebuilt with the same mother board and a Q9650 and 2 GTX470s in SLI. Again the frame rates in most games are high but it “feels” choppy. I thought the issue was all in my head.
Does this mean I’m not nuts?
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1
August 22, 2011 5:35:19 PM

lradunovic77As I said even if someone tried to change refresh rate it wont be possible cause there not even an option to do so.



if "John" read what you posted and took your advice and bought a shinny new 120Hz to fix his micro stuttering only to be greeted that his micro stuttering is still apparent


120Hz aren't cheap


you should stop giving advices unless you tried and tested that it works or alteast have a data to backup your "claims"
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3
August 22, 2011 5:35:38 PM

One thing you never did and that's to replace monitor. I found Samsung LCD Monitor absolute crap for gaming (feels choppy). My good experience was with LG and ASUS here and there.
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-7
August 22, 2011 5:38:11 PM

Forgot to mention Acer as well!
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-6
August 22, 2011 5:42:42 PM

I just want to say that I had severe micro-stuttering in most of my games (Black ops, Farcry 2, Metro 2033, Gtaiv, ect. ect.) when I upgraded from a single gtx 480 to dual gtx 480's in sli. I really thought it was the graphics cards that caused it, as with a single card it was gone. I tried so many things to fix it, including purchasing a new sli bridge. I was to the point I gave up on the problem and just dealt with it. I had micro-stuttering at all frame rates even 100+ fps in some games, and in every game it went away if I turned off SLI.

Skip a few weeks later after buying my second card, I decided to upgrade my ram. I was running Corsair 3GB (3 x 1GB) DDR3 1333, and even though my ram never went above 90% in any game I still decided to upgrade my ram because I do alot of multi-tasking. Anyways, I purchased a Corsair Vengeance 8GB kit, (2 x 4GB) DDR3 1600. After I installed the new ram, my microstuttering in all my games disappeared. I was sure it wasn't my ram, because I still had stuttering even when ram usage was below 60% in some games. I don't know if it was because I went from tri-channel to dual-channel, or if it was the speed, or the timings, or the amount of ram... ??? Not sure.

I read a lot of forums to try and fix my problem and they all failed. I was sure it was my graphics cards. I had a few people say I didn't have micro-stuttering, but by all definitions of micro-stuttering that i've read, that is what I had. And my problem, while it appeared to be graphic card related, it wasn't. Maybe the ram threw off the card timing, or maybe it was something else. I dunno..

I just want to say this was a very well written article, and it covered a lot, but it was lacking in one area, and that is what exactly causes micro-stuttering. I think to many people are too quick to blame the graphics cards. I mean, yeah that probably is the reason in a lot of systems, but i'm sure there are a lot of micro-stuttering that isn't caused by the gpu's.
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2
August 22, 2011 5:50:55 PM

I would love for AMD and NVIDIA to focus on quality more. fps doesn't tell the whole story.
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3
Anonymous
August 22, 2011 5:59:11 PM

EXCELLENT FREAKING ARTICLE! Wow, and to think I was shopping just today for a second AMD card. I will avoid this dual card nonsense like the plague until Tom's follows-up and gives the all clear. I will stick to single card configurations until that day.

This is a basic STATISTICS problem folks. It's called "VARIANCE". You remember those FPS graphs in those articles? They should be STRAIGHT HORIZONTAL LINES, not ups and downs. UP + DOWN = MICROSTUTTER.

Too much in computing (and in life) focuses on QUANTITY (FPS!) but not enough testing goes into evaluating QUALITY (reduced variance!).

BRAVO TOM'S HARDWARE! The emperor has no clothes!
Score
7
August 22, 2011 6:20:26 PM

i personally havent noticed any microstuttering with my hd6870's but this article certainly makes me feel like a jerk, especially for recommending the setup to anyone. also a little sad because tom's has been recommending hd6850's and hd6870's in crossfire for what, 8 consecutive months? ruined my day.
Score
7
August 22, 2011 6:52:10 PM

Perhaps with articles like this one, Nvidia and AMD will take notice.
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4
August 22, 2011 7:20:26 PM

I used to get crazy tearing with my 2 GTX 275's.
The latest drivers seem to have killed off most of the problems but I still cant help but want to move to the latest generation of cards. (Itching for a GTX580 or 2) But the prices on these cards are still a bit unrealistic in my opinion. Im wondering if it would be beneficial, after reading this article to dig up an old 275 from ebay or something and go 3 way sli.

Great article!
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0
August 22, 2011 7:21:09 PM

wait... the cpu is at 5GHz!? ddaaaaaannnnnngggggg
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1
August 22, 2011 7:24:46 PM

edubz9

You know, I'm going to give you a thumbs-up because I can't quite figure out what you're smoking and I'd like some, please. :p 
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1
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