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Do crossfire setups have to be the same make of card?

Discussion in 'Video Cards & Monitors' started by Caffeine Dealer, Feb 12, 2011.

  1. Caffeine Dealer

    Caffeine Dealer Member

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    As the title suggests....

    Just curious to know if i was to buy another 6870 to match the current one, does it have to be made by the same company ie Sapphire?

    I would want to buy the same for obvious reasons but say i could get a Gigabyte 6870 for cheap ... would it work
     
  2. dukkie

    dukkie Member

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    Not at all, with Crossfire you can get any of the same kind of card eg. Gigabyte HD6870 and Sapphire HD6870. If one is clocked higher than the other, the higher clocked card will drop its clocks to the same as the slower card.

    Hope this helps :)
     
  3. Alba

    Alba Member

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    Any 6870 or even any 6850 will work with your current card.

    That's the beauty of crossfire.
     
  4. OP
    OP
    Caffeine Dealer

    Caffeine Dealer Member

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    What about my 6870 + a 6950?

    The 6950 clocks at 800mhz which is 100mhz lower than my 6870 but it has the 2GB of memory?

    So let me get this right... the 2 cards will only ever clock to the settings of the lowest clocked card. How does Crossfire effect memory?
     
  5. WishBone17

    WishBone17 Member

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    hell no.
    i had an asus 5870 and an HIS 5870
     
  6. Frontl1ne

    Frontl1ne Member

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    I'm curious about this as well.

    I've read that memory is independant for each card (so one is not restricted by the other). But if both cards are supposed to have identical work load in crossfire mode, and if the 1GB runs out of VRAM, then does that mean the 2GB will not use it's extra RAM since both should be going through the same amount of work load?

    Or am I totally on the wrong track :rolleyes:
     
  7. OP
    OP
    Caffeine Dealer

    Caffeine Dealer Member

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    Sounds feasible ....

    Firstly i'm not actually sure i can Crossfire a 68 series with a 69 but if its possible, i really hope that it gives a total sharable memory of 3gb.
    It looks as though i can score a 6950 for only $80 more than an additional 6870.
    I know i would pay $80 for an additional 1gb of DDR5 ram on my current card if i could.

    I'm also wondering if it's worth grabbing a 6850 and overclocking it to 900mhz. This seems to be possible from my Google searches. Problem then is... i have to return my 6870 down 100mhz an that would be a shame.
     
  8. Alba

    Alba Member

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    Only the same series, for eg, 5830, 5850, 5870 and 5970 can all CF.

    Not 100% sure with the 6870 and 6950 but I don't think so as they need to be using the same GPU like the 5 series above do.

    You are correct, the card with more mem will only use the amount that the card with less has.
     
  9. OP
    OP
    Caffeine Dealer

    Caffeine Dealer Member

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    Ok so that makes buying a 6950 to go with my 6870 useless even if it will work in crossfire....
    What about adding a 6850 to my 6870?
    Would there be a notable increase? Will i be wishing i just spent the extra $ to get the additional 6870 or is the end result much the same one the 6850 is overclocked as a stock 6970?

    Are the hotter temps of the 6850 due to smaller heatsinks?

    I have noticed from reviews of Crossfired 6870's that the most notable difference over stock is when you are using higher resolutions. How will this effct my Eyefinity setup?

    The reason i ask is...
    I noticed an increase of around 10 degrees c and a loss of around 10 - 20 FPS over stock when i hooked up the additional 2 monitors. Is there a chance that the pair will run cooler than a single stock 6870 even with Eyefinity?
     
  10. Alba

    Alba Member

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  11. OP
    OP
    Caffeine Dealer

    Caffeine Dealer Member

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    I cant view the for sale section. I dont think i have been a member for long enough or maybe i dont have enough posts or something?
     
  12. Pemalite

    Pemalite Member

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    Yep, can't crossfire a 69xx with a 68xx because of changes to the architecture.
    The 69xx series employs the 4VLIW shader array whilst the 68xx series uses the older 5VLIW shader array, plus their was allot of other changes to other parts of the architecture like Tessellation and ROPS and such.

    Then about memory sizes... If one card has 512mb and the other has 1024mb then they will both be limited to 512mb.
    Clock speeds of the higher speed card will also drop down to the lowest common denominator.

    Always try to use cards of the same type (Like a 6870+6870 setup) and with the same memory size and type (1gb GDDR5 with 1gb GDDR5 for instance).

    Otherwise Crossfiring a 6870 and a 6850 will achieve the same results as a Crossfire 6850 set-up, and the extra you paid for on the 6870 was essentially wasted.
     
  13. Archy

    Archy New Member

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    And to put to rest the idea of a 3GB memory pool, I'm pretty certain that each GPU can only access its own memory and that it's essentially mirrored in Crossfire, to use a RAID analogy, so two 6870s will still present 1GB VRAM to work with.
     

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