We previewed AMD's CrossFireX technology a couple weeks ago, but today a WHQL drier is available that supports more than two AMD GPUs. In order to do this, AMD employs Vista's Linked Display Adapter (LDA) technology to make the collective GPUs appear to the system as a single virtual device. While this allows for more flexibility in GPU configurations, there are some drawbacks that we will talk about shortly.

The new Catalyst 8.3 is a milestone release for AMD that brings, in addition to Vista LDA support for more than two GPUs, a number of new features. These are (from AMD's documentation):

ATI Hybrid Graphics Support: The ability to use integrated and discrete graphics in hybrid mode to support either power saving (disabling the discrete graphics card) or to enable the integrated and discrete graphics hardware to share the graphics load. This is only available with lower end graphics cards and integrated chipsets using the 3200/3300 series hardware.

Anti-Aliasing enhancements: AA support for all UE3 titles (Unreal Tournament 3, Gears of War, Rainbow Six, etc.) through the control panel. Support for edge detect filters plus Super AA was slated to be in this release but it was pushed back. Tent filters can be enabled with Super AA, but edge detect will be coming soon.

Digital Panel GPU image scaling: The option to enable image scaling for maintaining aspect ratio of a display has been added. Additionally, the GPU itself is now used to scale the image if the check box is ticked. NVIDIA has had this for a while and it's good to see AMD adding support for this.

Advanced Video Quality controls: An edge enhancement slider has been added to adjust the sharpness of the video playback, along with a noise reduction slider. Having variable adjustment for these kinds of features is a very welcome addition and something we've been wanting ever since noise reduction became a hot topic in video decoding.

HydraVision for Vista: Multiple monitor and virtual desktop manager with support for hotkeys and tools to help keep things organized.

Let's take another look at CrossFireX now that we are allowed to test it on Intel hardware and compare it with competing solutions.

Setting it Up …


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  • DerekWilson - Saturday, March 8, 2008 - link

    that is key ... as is what ViRGE said above.

    in addition, people who want to run 4 GPUs in a system are not going to be the average gamer. this technology does not offer the return on investment anyone with a midrange system would want. people who want to make use of this will also want to eliminate any other bottlenecks to get the most out of it in their systems.

    not only does skulltrail help us eliminate bottlenecks and look at the potential of the graphics subsystem, in this case i would even make the argument that the system is a good match for the technology.
  • Sind - Saturday, March 8, 2008 - link

    I agree, I don't think the Skulltrail is doing anyone favours of how they could judge utilising these MGPU solutions in a "average" system that the reader on Anand would be using. X38 seems very popular as is 780i, I really don't think even more then 1% of your traffic would ever utilise the system you used to do this review. I've read the other CrossfireX reviews from around the net, and most had no problems at all, and infact most noted that it worked straight out with no messing around with the lengthy directions that were indicated in the article to get it to work. Reply
  • ViRGE - Saturday, March 8, 2008 - link

    Something very, very important to keep in mind is that Skulltrail is the only board out right now that supports Crossfire and SLI. If AT wants to benchmark both technologies without switching the boards and compromising the results, this is the only board they can use. Reply
  • Cookie Monster - Saturday, March 8, 2008 - link

    No 8800Ultra or GTX Tri-SLI for comparison? Reply
  • DerekWilson - Saturday, March 8, 2008 - link

    we were looking at 2 card configurations here ... i'll check out three and four card configs later Reply
  • JarredWalton - Saturday, March 8, 2008 - link

    Unfortunately, Tri-SLI requires a 780i motherboard. That's fine for Tri-SLI, but CrossFire (and CrossFireX) won't work on 780i AFAIK. I also think Skulltrail may have its own set of issues that prevent things from working optimally - but that's conjecture rather than actual testing. Derek and Anand have Skulltrial; I don't. Reply
  • Slash3 - Saturday, March 8, 2008 - link

    ...graphs are both using the same image. The Oblivion Performance and 4xAA/16AF Performance line graphs (oblivionscale.png) are just duplicates and link to the same file. :) Reply
  • JarredWalton - Saturday, March 8, 2008 - link

    Fixed, thanks. Reply
  • slashbinslashbash - Saturday, March 8, 2008 - link

    Graphics really are fairly unique in the computing world in that they are easily parallelized. While we're pretty quickly reaching a point of diminishing returns in number of cores in a general-purpose CPU (8 is more than enough for any current desktop type of usage), the same point has not been reached for graphics. That is why we continue to see increasing numbers of pipelines in individual GPU's, and why we continue to see effective scaling to multiple cards and multiple GPU's per card. As long as there is memory bandwidth to support the GPU power, the GPU looks like it is capable of taking advantage of much more parallelization. I expect 1000+ pipes on a 2-billion-transistor+ GPU by 2011.

    So, I expect multi-GPU to remain with us, but any high-end multi-GPU setup will always be surpassed by a single-GPU solution within a generation or two.
  • DerekWilson - Saturday, March 8, 2008 - link

    that's not the issue ... graphics is infinitely parallelizeable ...

    the problems are die size and power.

    beyond a certain die size there is huge drop off in the amount of money and IHV can make on their silicon. despite the fact that every chip could have been made larger, we are working with engineers, not scientists -- they have a budget.

    multiGPU allows IHVs to improve performance nearly linearly in some cases without the non-linear increase in cost they would see from (nearly) doubling the size of their GPU.


    then there is power. as dies shrink and we can fit more into a smaller space, will GPU makers still be able to make chips as big as R600 was? power density goes way up as die size goes down. power requirements are already crazy and it could get very difficult to properly dissipate the heat from a chips with small enough surface area and huge enough power output ... ...

    but speading the heat out over two less powerful cards would help handle that.


    in short, multigpu isn't about performance ... it's about engineering, flexibility and profitability. we could always get better performance improvement from a single GPU if it could be built to match the specs of a multiGPU config.

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