Graphics is infinitely parallel. There is always more work that can be done, and the work can be broken up into millions of completely independent operations. This is very different than most tasks we see done on the CPU that don't scale quite as easily with the number of cores. While we might see small improvements by adding another CPU, we can see nearly double the performance by doubling the number of processors in a graphics card (as long as there are no other bottlenecks anyway). This fact is why AMD and NVIDIA have invested so much money into their respective multiGPU solutions (CrossFire and SLI respectively).

MultiGPU solutions have been around for a few years now, and while we frequently include single card multiGPU solutions in our reviews, we only occasionally take an in depth look at multiGPU technology. Some time has passed since the last time we studied the issue, and now that we've fully broken in our Core i7 system, 64-bit Vista, and recent graphics drivers, it's time to get to it.

Over the past few weeks we've been benchmarking and analyzing lots of numbers. We've looked at single, two, three and four GPU systems across multiple games and resolutions. The configurations we chose to look at are current generation high-ish end hardware capable of operation in 3-way and 4-way configurations. Because of the sheer volume of data we collected, we've decided to break up our analysis into multiple articles.

This first article (the one you're reading right now) will cover single and dual GPU configurations (including single card multiGPU hardware). The next article will add 3-way solutions along with comparisons back to single and dual GPU setups. The final article will add in 4-way performance analysis and compare it back to the single, dual and 3-way data. Splitting up the analysis this way will allow us to dive deep into each type of configuration individually without spreading the content too thin. We can keep focus on a specific aspect of multiGPU performance and scaling while still making all the relevant comparisons.

The initial installment also introduces the Sapphire Radeon HD 4850 X2 2GB. Though we expected AMD to push the 4850 X2 out in the same way they launched the 4870 X2, we've only seen one version of the 4850 X2 hit the scenes late last year from Sapphire. In light of what we've seen, we are rather surprised that we haven't seen more fanfare behind this part from either AMD or other board makers. The lighter weight X2 competes more directly in price and performance to the GeForce GTX 280/285, and really fills out the lineup for AMD. Overall, the increased RAM in the 4850 X2 2GB enables great performance scaling even at resolutions the 512MB 4850 can't come close to handling.

As for the topics we'll cover, our interest will focus on scalability of the multiGPU solutions and the relative value of the same. Before jumping into the numbers, we'll cover the metrics we use to analyze our data. First, we'll look at scaling and talk about the big picture. Then we'll talk about what we've done to calculate a value comparison.

Who Scales: How Often?
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  • 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 -
    BUT THE RED RAGE FUD NEVER ENDS.
    ( 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.)
    Reply
  • Hrel - Thursday, March 05, 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:
    http://www.anandtech.com/video/showdoc.aspx?i=3437...">http://www.anandtech.com/video/showdoc.aspx?i=3437...
    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.
    Reply
  • 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.
    Reply
  • 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:)

    Z.
    Reply
  • 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.
    Reply
  • 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
    Reply
  • 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.
    Reply

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