The Test

Test Setup
CPU AMD Phenom @ 2.6GHz
Motherboard MSI K9A2 Platinum
Video Cards ATI Radeon HD 3870 X2
ATI Radeon HD 3870
Video Drivers Catalyst 8.1 (Modified for CrossFireX Support)
Hard Drive Seagate 7200.9 300GB 8MB 7200RPM
RAM 2x1GB Corsair XMS2 DDR2-800 4-4-4-12
Operating System Windows Vista Ultimate 64-bit


We ran the following games in their corresponding quality settings:

Game Resolution AA AF Detail Settings
Half Life 2: Episode Two 2560 x 1600 8X 16X Highest in-game
Unreal Tournament 3 2560 x 1600 0X 16X Highest in-game
Bioshock 2560 x 1600 0X 1X Highest in-game
Call of Duty 4 2560 x 1600 4X 16X Highest in-game
Crysis 1920 x 1200 0X 1X

High Quality defaults


The graph below shows the performance levels you can get from a single GPU all the way up to four: 

Obviously the biggest jump comes from one to two GPUs, but we still see some reasonable gains going from two to three. The value of a fourth GPU is simply nonexistent in most of the cases.

Number of GPUs HL2 UT3 Bioshock CoD4 Crysis
1 x Radeon HD 3870 39.3 46.7 36.9 25.3 14.0
2 x Radeon HD 3870 (1 X2) 71.9 84.1 63.2 50.0 26.2
3 x Radeon HD 3870 (2 X2 + 1) 93.3 112.7 86.7 72.2 26.4
4 x Radeon HD 3870 (2 X2) 102.2 114.6 92.5 93.2 27.7


Let's put some percentages with the graph above to put things into perspective:

Configuration HL2 UT3 Bioshock CoD4 Crysis
2-way CF Improvement over 1 card 83% 80% 71% 98% 87%
3-way CF improvement over 2 cards 30% 34% 37% 44% 0%
4-way CF improvement over 3 cards 10% 3% 7% 29% 4%
4-way CF improvement over 1 card 160% 150% 151% 268% 98%


The move from one to two cards generally yields a healthy performance improvement, but the gains taper off as we look at the performance added by a third GPU. Call of Duty 4 is the only game that shows solid gains with 4 GPUs (29% over a 3-GPU configuration), the rest of the titles show mostly single-digit percentage improvements.  Once again we see that Crysis simply needs new, faster GPU architectures - four GPUs does absolutely nothing for this game.

Remember our 3-way SLI review from earlier in the year? Although the test systems were very different, the GPU-bound scaling should be comparable (if anything, NVIDIA should have the advantage of being run on an Intel system). Here's a quick look back at some of the comparable benchmarks:

Configuration UT3 CoD4
2-way SLI Improvement over 1 card 84% 90%
3-way SLI improvement over 2 cards 20% 28%
3-way SLI improvement over 1 card 121% 143%


Single to dual GPU scaling is similar with SLI as CrossFire, but the 2-way to 3-way gain is better on CrossFireX. NVIDIA's quad-SLI is not yet available so we're not sure how the 4-way scaling will compare, but so far it seems like CrossFireX is doing quite well in the pure numbers game.

Drivers and Requirements Power Consumption & Final Words
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  • Spacecomber - Friday, February 22, 2008 - link

    Having recently read the preview of the 9600GT at Anandtech, one of the things that stood out from that article was how SLI seemed to do better than Crossfire on the games that were tested. Crysis was the only game that was used in both this article and that one, and 3850's were run in Crossfire for the earlier article, not 3870's. Nevertheless, it looks like Crossfire performance gains going from 1 to 2 ATI cards is now on a par (with the new AMD/ATI drivers) with going from 1 to 2 Nvidia cards.

    Perhaps this will prove to be the reason for AMD/ATI selecting the tests they did in this preview. CrossfireX does about as well SLI on these particular games?

    (Though we'll not see the results, we know that Derek is trying these new ATI drivers out on his Skulltrail system, if it's possible. ;-) )
    Reply
  • Zoomer - Thursday, February 21, 2008 - link

    Are you allowed to only test these games, or allowed to publish and talk about these games only?

    I don't see how ATi can enforce such a requirement. *cough* ghost *cough*

    Reply
  • Wirmish - Thursday, February 21, 2008 - link

    PC Perspective also test the beta-CrossFire-X.
    Their system is identical, except for the hard disk.
    http://www.pcper.com/article.php?aid=523&type=...">http://www.pcper.com/article.php?aid=523&type=...

    RÉSULTS:

    Bioshock
    Anand (0xAA/0xAF) -> 2=63, 3=87, 4=93
    PCPer (0xAA/8xAF) -> 2=65, 3=84, 4=92

    Call of Duty 4
    Anand (4xAA/16xAF) -> 2=50, 3=72, 4=93
    PCPer (4xAA/ 8xAF) -> 2=43, 3=56, 4=64

    Unreal Tournament 3
    Anand (0xAA/16xAF) -> 2=84, 3=113, 4=115
    PCPer (0xAA/ 8xAF) -> 2=58, 3=54, 4=58

    How do you explain these results ?


    POWER CONSUMPTION - ENTIRE SYSTEM

    Anand (Bioshock) -> 2=361W, 3=406W, 4=538W
    PCPer (CoD 4) ----> 2=407W, 3=527W, 4=663W

    Why didn't you choose the hungriest game to calculate the consumption of the system ?
    Reply
  • Paracelsus - Thursday, February 21, 2008 - link

    You've listed the 4-way CF over 1 card gain as 268%.

    It should be 368%. (95.2/25.3 = 3.68)

    The numbers are confusing, comparing 3-way to 2-way etc. Why do that, makes more sense to compare 3-way to 1-way. Then it's easy to compare to the perfect scaling of 200, 300, 400%.
    Reply
  • mechwarrior1989 - Thursday, February 21, 2008 - link

    I got confused by it to but the Test Bench isn't what they listed on the page. Either that's a Typo or that's just supposed to refer to the Nvidia Benchmark that they did with the Tri-SLI Reply
  • kalrith - Thursday, February 21, 2008 - link

    Yeah, it looks like they entered the test setup from the Nvidia article rather than the one used in this article. It would make sense if they entered both test setups but not to completely exclude the AMD setup used for most of the tests. Reply
  • Anand Lal Shimpi - Thursday, February 21, 2008 - link

    Woops :) Fixed :)

    Take care,
    Anand
    Reply
  • Arbie - Thursday, February 21, 2008 - link

    Good catch for Anandtech! AMD told you it was a Phenom board but you saw it was really a QX9650. The company must be in dire straits to try a trick like that. Sad. Reply
  • donkeycrock - Thursday, February 21, 2008 - link

    The graph is the best and most effective one i've seen in anybody's review in a long time. cheers and well done Reply
  • brunis - Thursday, February 21, 2008 - link


    Hi, alot of people are still playing WoW, me included. I just bought the Samsung 245B, a wide 24" screen. I'd love to see a cpu+gpu update for the wow guide. If i should invest in an extra 8800GTS or a new Core2 or AMD Phenom cpu.

    regards,
    Brunis
    Reply

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