Who Scales: How Often?

A major topic in the multiGPU arena is software support. And there are two large factors here: how many titles benefit and how much do those titles benefit. In the past we've seen SLI provide scaling more frequently and consistently than CrossFire (especially right when games come out). With CrossFire we'll often see support for older games get broken in newer drivers and then fixed when a review site happens to stumble upon the issue. But we've also noted that when CrossFire worked, it worked really well. It's honestly been a long time since we did a quantitative analysis of how SLI and CrossFire really stack up as technologies, and there's no time like the present.

First we will explore whether performance scaling happened in our suite of games. We've looked at two different metrics to judge our cards, both of which look at percent increase from 2 GPUs. If we consider the success of a multiGPU solution to be contingent on a performance improvement of at least 30% out of a possible 100%, we can count the number of times we see success in our benchmarks as a benchmark. We ran 21 different tests (7 games at 3 different resolutions), so keep that in mind when looking at this of list successes per configuration.

NVIDIA GeForce GTX 285 17
NVIDIA GeForce GTX 280 18
NVIDIA GeForce GTX 260 20
NVIDIA GeForce 9800 GTX+ 19
ATI Radeon HD 4870 512MB 17
ATI Radeon HD 4850 19
ATI Radeon HD 4870 1GB 16

Since this takes into account CPU limited cases, our higher performance SLI and CrossFire solutions will see cases where 1680x1050 or even 1920x1200 isn't a high enough resolution to allow for any real improvement. Cards that look good by this metric are ones that both scale well and start off at a low enough performance point so as to allow good scaling to happen even at lower resolutions (well, lower for multiGPU application anyway). This shows the GTX 260 and the 4850 hit a sweet spot in terms of scaling and baseline performance in modern games to provide benefit for a larger number of users (many more people have 1680x1050 and 1920x1200 than 2560x1600 monitors). Because this 9800 GTX+ is older, we see headroom here too.

If we exclude the simply CPU limited cases and look at cases where the multiGPU solution got near zero or negative performance improvement we see a slightly different picture. Our data is on a per game basis, so all of these numbers are out of 7.

NVIDIA GeForce GTX 285 7
NVIDIA GeForce GTX 280 7
NVIDIA GeForce GTX 260 7
NVIDIA GeForce 9800 GTX+ 6
ATI Radeon HD 4870 512MB 6
ATI Radeon HD 4850 5
ATI Radeon HD 4870 1GB 7

This shows cases where certain multiGPU configurations have zero value to help improve performance because of some failing of the graphics solution. All these cases happen to be issues at 2560x1600 where the resolution proved too much to handle because of the limited amount of onboard RAM.

It's also important to point out that the Sapphire 4850 X2 doesn't suffer from the problems of the 4850 CrossFire we show here. The Sapphire card scales and performs well in every test we ran.

Index Who Scales: How Much?


View All Comments

  • SiliconDoc - Wednesday, March 18, 2009 - link

    1.Let me help you out. More people have 1280x1024 monitors, and any who do have flat panels, are most likely stuck at 1680x1050 because the 1920x monitors command a premium.
    So MOST GAMERS are far below 2650, and 1920, and even 1650, and some can't run 1280x1024.
    A common game rez is 1024x768, 800x600 is also used currently on all the high end games - both especially with gamers with brand name store bought systems - we all know the big names ( not the multiple thousand dollar gaming brands - that's one of 50 gamers!). When you're stuck in a lab with $2,000 monitors and then travel to checking out the cebit babes, staying in touch with the average gamer is difficult, to say the least.
    2. Even though the 260 passes 20 of 21 tests, and the 4850 passes LESS, Derek the red just HAS to state that the Sapphire passed every test they threw at it. Now the upper number doesn't jibe with that - the one showing the 4850 worked in LESS situations than the GTX260 -
    ( obviously more than one 4850 brand was in play - NEVER THE LESS - that is the type of CONSTANT red slant that is all over EVERY SINGLE PAGE.)
  • Hrel - Thursday, March 5, 2009 - link

    I found an oddity. This articles posted power consumption doesn't correspond to other articles findings; yes I know I can't cross reference data across articles. In this article:
    The 9800GTX+ uses less energy than the HD4850 and in this multi-GPU article it's the other way around. I know I can't compare total system power findings but I'd think that the cards would at least be in the same order.
    Can someone PLEASE clear this up for me? I'm very confused as to which card is more power efficient as the findings have varied so heavily across different articles.
    It would probably be a good idea to list the power consumption of only the GPU, instead of the whole system. Doing that would remove variables, which is of course, a goal of any scientific experiment.
  • Hrel - Friday, February 27, 2009 - link

    I just wanted to say, this is a great article. I'm glad you guys finally wrote an article comparing pretty much every card out there that people will consider buying, you could have included some lower end cards and resolutions. But hey, it takes a lot of time to do that many tests accurately; I appreciate all that you did do. It really was a well written and interesting article to read; good job anandtech.
    P.S. Any news on when new GPU's will be coming from Nvidia/AMD. I've noticed a LOT of price drops and mail in rebates on GPU's recently.
  • Zak - Wednesday, February 25, 2009 - link

    "In general, more than one GPU isn't that necessary for 1920x1200"

    Depending on the definition of "that":) I disagree, gameplay is so much smoother with two cards on a 24" monitor. I tried playing with one 285 versus two, and while I don't have any real numbers, the differences is very noticeable. Crysis never dips below 40fps. This is my first real SLI since Voodoo II and I'm very glad I did it. You can always buy one card and decide if you want the second one later. I paid under $700 for two 285s and also got a copy of World at War and FarCry2 with two cards (a fluke maybe), that's almost $100 worth of games:)

  • magnusr - Wednesday, February 25, 2009 - link

    Im currently using an ATI 4850 512MB at 1920x1080 on an x58 chipset system.

    I just ordered another 4850 for crossifre usage due to this article.

    Thanks for the tip. Keep up the good work.
  • GoodRevrnd - Wednesday, February 25, 2009 - link

    I know it's 2 years old, but it is still a relatively taxing game for it's age and is still relevant with the Tales of Valor expansion coming out... so could you PLEASE add Company of Heroes back into your reviews? I would just ask for Dawn of War 2 benchmarks, but it's the same engine and they didn't include a nice performance test. As it stands there are no RTS's in your hardware reviews. I'd just like to see a broader spectrum of games represented. Reply
  • Razorbladehaze - Wednesday, February 25, 2009 - link

    I second the motion to include CoH. Reply
  • poohbear - Wednesday, February 25, 2009 - link

    i gotta commend u on ur graphs, very clean and very easy to understand unlike some other sites that have confounding line graphs. i especially love how i can choose between different resolutions to see the diff instantly. Kudos to u guys.:) Reply
  • Nighttrojan - Wednesday, February 25, 2009 - link

    I upgraded my gpu awhile back and got a MSI 4870 1 gig (ATI) card to replace my old MSI 7600gt 256 mb (Nvidia). However, although I can get better quality graphics with the ATI card, the Nvidia card is actually faster when playing Vanguard soh.... The game loads slower and takes more time shifting graphics (graphic lag), but the graphics look better and I can turn up settings a little higher. Any ideas on what's going on?

    Early Core2Duo 6600
    Early ab9 pro abit motherboard
    All drivers up to date
  • Razorbladehaze - Wednesday, February 25, 2009 - link

    Any time you increase graphics settings on a game you increase the amount of information that needs to be off loaded to and from HDD, CPU, RAM, GPU so this is likely you reason for slower load times.

    But that card is in not actually "faster" than the 4870, in actuality that card is probably 2-3x better at rendering then the 7600 across all games.

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