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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  • DerekWilson - Monday, February 23, 2009 - link

    It really is a great looking game for an MMO. It's not the most played MMO around, but it is definitely the easiest to test. There is an area near the beginning where the player is alone in the environment and it's always the same time of day and all that stuff ... It takes out some of the factors that make getting consistent data out of other MMOs incredibly difficult.

    I've never had any real "issues" with it or with the results either. It's been very consistent as well. It does add value, and it's clear that games can be coded in a way that looks really good and perform like this one, so we feel it's important to getting a better feeling for what's out there and what's possible.
  • IKeelU - Monday, February 23, 2009 - link

    Not really a big deal, but could you cut out the offhand game review comments when introducing benchmarks? I.e.: "Crysis Warhead, while not the best game around..." It feels out of place in a hardware analysis. Reply
  • SiliconDoc - Wednesday, March 18, 2009 - link

    And Derek disses Far Cry 2 and Oblivioin where nvidia slaughters ati - then derek praises Bioshock where ati has an edge.
  • SiliconDoc - Wednesday, March 18, 2009 - link

    Oh yes, and below don't forget the age of conan that favors the ati card - Derek can't stop drooling all over the place.
    Then come to COD, where nvidia once again slaughters - red blood everywhere - Derek says "do we really need another war game~" or the like.
    Derek is red fan central and cannot stop himself.
  • The0ne - Monday, February 23, 2009 - link

    This game is poorly programmed in the first place, does it deserve to even be included in the benchmark tests? Yes, it has the programming necessary to for the test but they're poorly programmed. Reply
  • IKeelU - Monday, February 23, 2009 - link

    The fact that CryEngine 2 is taxing on today's hardware (and that Crytek will no doubt use derivatives of it in future games), makes it very useful in benchmarks. I hope reviewers keep using it. But by all means, feel free to disassemble Crytek's binaries and point out their code's weaknesses.

    Yeah, I thought not.
  • poohbear - Wednesday, February 25, 2009 - link

    what do u mean they shouldnt include crysis warhead??? its the seminal game to see how graphics performance is to get an idea of how a particular video card will perfrom in the future. Cryengine2 is the most advanced graphics engine on the market. If a video card can provide 30 fps on a cryengine @ your resolution, then its good to last u for atleast 2 years. Reply
  • Razorbladehaze - Wednesday, February 25, 2009 - link

    Yeah.... NO.

    I totally disagree with it being the most advanced. It is a decent game engine especially for benchmarking, but....

    In all reality the STALKER Clear Sky revamped xray engine is far and away more advanced and superior in almost every way. It is about the same or better in regards to taxing the system (low frame rates does not necessarily translate to the game is taxing the system.). Being that these are also used in similar FPS titles they would make a interesting comparrison.

    I would really like to see Anand include or swap a clear sky bench (there is a premade one available), for the Crysis or Crysis warhead. Either way no big deal many other sites post results with a CS bench that view all the time.

  • DerekWilson - Monday, February 23, 2009 - link

    i'll take care of it. Reply
  • Stillglade - Monday, February 23, 2009 - link

    I would love to see more info about the 4850 X2 1GB version. For over $50 cheaper, is the 1GB memory enough to compete? Is it worth paying 24% more for the 2GB version that you reviewed here? Reply

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