Sign in with
Sign up | Sign in

PCI Express & CrossFire: Scaling Explored

PCI Express & CrossFire: Scaling Explored
By

AMD’s CrossFire technology might be an excellent way to turn a mundane gaming machine into an FPS-shredding powerhouse, but with multiple Intel-based platforms supporting the feature across several different PCI Express lane configurations, not everyone is equally convinced. Putting aside the fact that many games only benefit from CrossFire at high resolutions and high-quality settings, many users are concerned about whether or not their motherboard can provide enough bandwidth to realize the full potential of CrossFire.

We hear questions like, “should I upgrade my motherboard first ?” and “CrossFire Upgrade or New Build” in our user forums, with a different set of answers each time. It’s time to put some data behind those responses.

Five Core 2 motherboards from ASUS, ready for testingFive Core 2 motherboards from ASUS, ready for testing

With Core 2 chipset development halted in light of Core i7 and recent worldwide financial events causing many buyers to re-evaluate their spending habits, now is the perfect time to analyze how CrossFire scales on various chipsets as a guide for those looking to enable the best possible performance at the right price.

Digging deep into our hardware stash, we found Core 2-compatible motherboards going all the way back to the venerable 975X chipset, along with every generation of Intel LGA775-based motherboard since.

Of course, we had to pick a starting point, so today’s article brings with it all the prior upgrades that owners of high-end systems up to two years old could reasonably be expected to have purchased, such as Intel’s fastest Core 2 Duo processor and four gigabytes of high-speed memory. Follow along as we detail each build and attempt to determine which motherboards are suitable for CrossFire upgrades and which are better retired to platform heaven.

Display 96 Comments.
This thread is closed for comments
  • 2 Hide
    badge , December 8, 2008 7:16 AM
    Thanks for laying that information out.
  • 5 Hide
    sparky2010 , December 8, 2008 7:31 AM
    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!
  • -1 Hide
    V3NOM , December 8, 2008 7:32 AM
    yer kinda interesting to see how things have changed with new mobos but it doesnt really have any practical value tbh.
  • 5 Hide
    Crashman , December 8, 2008 7:38 AM
    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.
  • 0 Hide
    outlw6669 , December 8, 2008 7:50 AM
    Thanks for finally getting this review out!
  • 1 Hide
    arkadi , December 8, 2008 8:07 AM
    p45 looks grate, and the price is right.
  • -9 Hide
    arkadi , December 8, 2008 8:08 AM
    btw x58 is out there, just a reminder.
  • 1 Hide
    outlw6669 , December 8, 2008 8:20 AM
    @ 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.
  • 2 Hide
    Crashman , December 8, 2008 8:21 AM
    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.
  • -1 Hide
    arkadi , December 8, 2008 8:41 AM
    Yeah I know, the comment was in general...
  • 0 Hide
    dimaf1985 , December 8, 2008 9:51 AM
    great article. consise and informative at the same time. now if only there was one for amd chipsets...
  • 0 Hide
    marraco , December 8, 2008 11:39 AM
    Good work!.

    Altought, I have an Athlon X2 system, and probably gonna update to a I7 920. It would had be better comparing to an cheap i7 as a reference
  • 1 Hide
    Lurker87 , December 8, 2008 11:59 AM
    Excellent info. It'll be nice having this article to link to.
  • 5 Hide
    antiacid , December 8, 2008 12:34 PM
    This article shows that even in the best conditions, x48 vs p45 is at most 5% difference. Price-wise, this confirms my observations that the lower priced P45 boards are much better performance/value than the x48 premium counterparts.
  • 2 Hide
    Roland00 , December 8, 2008 12:44 PM
    I understand it is more testing, and you already had several months of delays but it would have been nice to see 1920x1200 numbers. 24" monitors are now in the mainstream affordability range with prices ranging from $249 to $349
  • 1 Hide
    waffle911 , December 8, 2008 12:54 PM
    I might be missing something, but it kinda looks like a Phenom 9950 paired with the 790FX SB750 would be comparable to the X48. But really, what am I missing? I can't find a direct comparison anywhere.
  • 0 Hide
    waffle911 , December 8, 2008 1:01 PM
    Sorry: bit of an oversight on my part. CPU charts of course, though the AMD board is using the older SB600, but the performance difference shouldn't be much different.
  • 2 Hide
    Crashman , December 8, 2008 1:03 PM
    Roland00I understand it is more testing, and you already had several months of delays but it would have been nice to see 1920x1200 numbers. 24" monitors are now in the mainstream affordability range with prices ranging from $249 to $349



    You're right! The problem is trying to test a whole bunch of different resolutions. 1920x1200 is almost right in the middle between 1680x1050 and 2560x1600, so hopefully most people can figure out "about" where that resolution would fall on the charts.

    Is it time to get rid of 1024x768? I'm in favor of ditching that resolution and picking a different one.
  • 0 Hide
    FlorinR , December 8, 2008 1:08 PM
    I'm trying to figure out something after reading this article, maybe someone could help me understand??? It seems that a SINGLE Radeon HD 4870 still have enough bandwidth into a PCI-E 1.1 slot, and the differences in performance compared to PCI-E 2.0 came from the chipset (P35 vs. P45 in SINGLE card configuration). Am i wrong?
Display more comments