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PCI Express & CrossFire: Scaling Explored

Performance Summary And Conclusion

If this were a standard motherboard review, we might simply throw up a single chart to show the overall performance differences between various CrossFire configurations, and it would look like this:

But while the simplified chart does show the problem of running CrossFire on P35 and P965 Express chipsets, it doesn’t really address the needs of individual buyers. The biggest concern will be the level of detail and resolution each gamer requires to reach a gaming-immersion comfort level.

At our lowest settings, the average gamer is best-advised to use a single card.

Increasing visual quality levels while maintaining a low resolution puts emphasis on memory performance, not graphics performance, as indicated by a significant win for the 975X motherboard.

Most middle-market buyers use either an old 1600x1200 display or a more modern 1680x1050 wide screen. At low-quality settings, the CrossFire performance advantage is generally too small to call any upgrade a good value unless a specific game requires the added performance.

Anyone who likes their games to look good and has at least a medium-resolution flat panel will love the performance boost CrossFire gives to our more modern motherboard choices. On the other hand, x4 pathways for the secondary graphics slots of P965 and P35 Express motherboards make any CrossFire upgrade a bad idea overall.

CrossFire really shines at 2560x1600, but anyone who can afford a 30” flat panel probably wouldn’t settle for low-quality graphics details.

Increasing detail levels enables even more value on the CrossFire solution, but anyone who can afford a 30” flat panel probably isn’t in the market for old system upgrades. Thus, the X48 and P45 results should be the only ones that matter at these settings.

Conclusion

Upgrading CrossFire-ready chipsets with a second graphics card is a great way for gamers to extend the useful life of their systems, as it provides nearly universal performance increases at medium to high resolutions and high details. Huge gains found on chipsets as old as the 975X prove that age isn’t a problem for buyers seeking a moderate-cost system renovation. Unfortunately, many other users don’t realize that their chipsets aren’t suitable for a CrossFire upgrade, in spite of any second or third graphics card slots.

Individual benchmarks showed that CrossFire performance is far too inconsistent on P35 and P965 chipsets to recommend it universally. In fact, several benchmarks suffered significant performance losses due to the low bandwidth of the second graphics card slot. Owners of these ill-equipped motherboards must carefully consider which games they’d like to continue playing before taking the plunge.

The easy solution for P965 and P35 Express systems is to simply use a single, more powerful card. At the very least, the issue we encountered where a secondary PCI Express x4 slot’s limited bandwidth hurt performance can be avoided by using a single card, so comments such as "CrossFire doesn’t work right" wouldn’t apply to single-card CrossFire solutions such as the HD 4870 X2. But the point of this article was to judge the viability of adding a second card when a reasonably good card is already installed, and this is an area where P965 and P35 Express motherboards simply cannot be upgraded to compete with modern builds.

  • badge
    Thanks for laying that information out.
    Reply
  • sparky2010
    should've included 1920x resolutions in the last page, as there are a lot of people out there with screens capable of that resolution.. but anyways, all in all a very good and informative article.. but i'm going to settle with a complete makeover when core i7 becomes more available!
    Reply
  • V3NOM
    yer kinda interesting to see how things have changed with new mobos but it doesnt really have any practical value tbh.
    Reply
  • Crashman
    V3NOMyer kinda interesting to see how things have changed with new mobos but it doesnt really have any practical value tbh.
    It's all about answering the question "Will a second card do the job".

    Lots of guys have midrange or better ATI graphics cards, and the question of "upgrade or replace" is constantly being asked.
    Reply
  • outlw6669
    Thanks for finally getting this review out!
    Reply
  • arkadi
    p45 looks grate, and the price is right.
    Reply
  • arkadi
    btw x58 is out there, just a reminder.
    Reply
  • outlw6669
    @ arkadi
    Yes the x58 is out.
    However, as it can not be paired with a Core 2 CPU and runs DDR3 exclusively, you can not directly compare the results.
    In general, I would assume crossfire on the x58 will scale similarly to the x38/48 as they both have the same PCIe configuration.
    Reply
  • Crashman
    outlw6669Thanks for finally getting this review out!
    It was planned for September but kept getting delayed due to tight deadlines on other articles. But when the economy finally went from a slow decline to a nosedive in November, we knew this article had to come out right away. More people are putting new systems on hold and looking for ways to keep their old ones up to current performance standards, and we care about upgraders just as much as system builders.
    Reply
  • arkadi
    Yeah I know, the comment was in general...
    Reply