Crossfired cards "not perfectly matched"?

Discussion in 'Videocards - AMD Radeon' started by ReDi, Feb 27, 2009.

  1. ReDi

    ReDi Member Guru

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    GPU:
    2x Sapphire HD4870 CF
    I just put in a 1GB HD4870 next to my older 512MB HD4870. CCC now says that the cards are "not perfectly matched" and says performance may not be optimum.

    I'm guessing that the message pops up because the cards have different memory sizes? If so, does that mean that only 1GB (2x512MB) will be used instead of the available 1.5GB?

    Is performance in any other way compromised, e.g. the second GPU is not fully utilized? Both cards have the same clock frequencies.

    I do see a (positive) performance difference in some games, so I guess it's not as bad as the CCC message suggests?

    Thanks in advance for your answers!
     
  2. ReDi

    ReDi Member Guru

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    Okay, after some more searching I found that my set-up will only have 512MB video memory, so not even 1GB :(.

    I am assuming that the second GPU is still fully used, though. If not, please post!
     
  3. rex1825

    rex1825 New Member

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    re:

    ...nope, it will have 512MB per card, that is 1GB bouth together, but problem is, it's again not 1GB, it's just 512 per card!

    It's like, every card will do it's job, but will have 512MB of VRAM to use...

    Cheers m8...
     
  4. ReDi

    ReDi Member Guru

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    OK, that's quite clear. Thanks!
     

  5. nutyo

    nutyo Ancient Guru

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    Yeah both the memory buffers have to be the same (data held in memory) for both the GPUs to be able to work on rendering the scene. Your setup will work exactly like having two 512MB cards in it. Do not worry there will be no other performance loss.
     
  6. LinkDrive

    LinkDrive Ancient Guru

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    You'll only need to worry about having more than 1gb of ram if your gaming higher than 2560x1600...which there's no monitor that can really support that kind of res unless you go triple monitors. So all in all, you'll be fine ^_^
     
  7. nutyo

    nutyo Ancient Guru

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    That's not true anymore. Games are coming out, and have come out, that would benefit from over 1GB vid ram even at 1920x1200. GTA 4 being the worst of the bunch, asking for >1.5GB.
     
  8. Iarwain

    Iarwain Banned

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    He's right. So far I don't know of any games which are unplayable with 512MB of VRAM but there are games where you could see a 10FPS or so boost with max textures and resolution.
     
  9. LinkDrive

    LinkDrive Ancient Guru

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    If your gaming at 1920x1200 then a 512mb card will do fine for most. I'm not saying there won't be a benefit to having a 1gb card, I'm just saying that you can achieve perfectly playable FPS with the eye candy cranked up. There's no game out there that chokes out a 512mb card to the point where it's unplayable at 1920x1200, even on max settings.
     
  10. ReDi

    ReDi Member Guru

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    OK, thanks. Just to get a little further on the memory usage: is rex1825 right that each GPU will have its own 512MB of memory, or will the dual-GPU combo only use 512MB, presumably the 512MB of the main card?

    Or will both GPUs use their own 512MB, but in each 512MB exactly the same data will be stored?
     

  11. dipanzan

    dipanzan Master Guru

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    yes he's right...

    dont worry...as for ur setup the the 1GB 4870 u'd function jst like a 512MB 4870

    so all in all...it u'd be like this>
    HD4870(1GB)+HD4870(512MB)=HD4870(512MB+512MB)CF
    Here the 1GB model u'd force down to ^^^(use half) of it's vram inorder to sync with 512MB model...thus operating in CrossfireX mode

    Hope this explains ur problem:)
     
  12. dipanzan

    dipanzan Master Guru

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    but at that rez...the GPU usually becomes the bottleneck & a card with 1GB vram u'd favor in intense graphics processing than a 512MB model

    Crysis for example u'd love the 1GB model over the 512MB model at that high rez
     
  13. salanos

    salanos Maha Guru

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    In your case; the 1024MB card will only be able to access 512MB of its personal 1024MB pool, while the 512MB card will be able to address its full 512MB.

    Multi-card/GPU set ups never address each others memory into a single shared pool.
     
  14. LinkDrive

    LinkDrive Ancient Guru

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    This is true, but even at 1920x1080, a single HD4870 512mb will average around 35-40 FPS if you have a decent custom config. And while the 1gb offers about a 5-10 fps boost, it's still not quite at the point where getting a 512mb card should be an issue.
     
  15. buddyfriendo

    buddyfriendo Ancient Guru

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    The memory is mirrored, since you have 1 card that is 512mb the 1gb card can only utilize 512mb.
     

  16. ReDi

    ReDi Member Guru

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    Thanks all, it's clear to me now. Contemplating upgrading the 512MB card to a 1GB card now :D.
     
  17. dipanzan

    dipanzan Master Guru

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    well I guess a 512MB 4870 suffice for the current games...but as newer games emerge...I think the 1GB model u'd be more preferred

    I really dont know the difference apart from what people say cuz I never owned a monitor with that kinda rez or even a 4870

    sry if I was incorrect on that matter
     
  18. bokah

    bokah Ancient Guru

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    i dont know about ur "max settings" but 4870 chokes on every game, well not tetris
     
  19. LinkDrive

    LinkDrive Ancient Guru

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    That's a typical statement coming from a GTX295 user.

    Look, I'm not going to sit here and argue with you. If you want to act like there's some sort of war going on and be narrow minded about it then that's fine, be my guest. But having owned two HD4870s, I can tell you from first hand experience that your information is bad information and I strongly suggest you do a little more research on the subject.
     
    Last edited: Feb 28, 2009
  20. buddyfriendo

    buddyfriendo Ancient Guru

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    Benchmarks on the other hand refute that statement completely.
     

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