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Thread: SLI & != video memory

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    mfr
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    SLI & != video memory

    Err... kinda newbie question here...

    Could two nvidia cards work in SLI if they have a different amount of video ram.
    In my case, could a 6600GT with 128mb work in SLI with another 6600GT but that has 256mb of ram.

    If it works, will the extra 128 mb on the second card be used or just ignored ?

    Thanks for any advice on this.

    MFR

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    Banhammer in peace PeterB kalniel's Avatar
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    Very good question.

    There's no way the extra 128mb ram on the second card would be used, but I as to whether it would work at all, I'm not sure. You might be able to flash the Bios of the 256 card to a 128mb model to fool the system.

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    Senior Member ajones's Avatar
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    Apologies for the cut'n'paste job from the nvidia website FAQ....

    Can I mix and match graphics cards with different sizes of memory?
    While it is not recommended, NVIDIA does offer this flexibility using Coolbits. When purchasing a second graphics card, you should try to match the memory size so that you are ensured full value and performance from your purchase. For example, if your first card is a GeForce 6600 GT with 128MB of memory, you should purchase a second GeForce 6600 GT with 128MB of memory. However, using Coolbits (value set to 18), you can force both of the cards to use the lower of the two memory sizes and operate together in SLI mode. When dissimilar memory sizes are enabled to work together using Coolbits, the effective memory size for each card becomes the smaller of the two memory sizes. Instructions to enable this feature can be found here.

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    So individually you have 384mb, but running SLI you'll only have 128mb!

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    Senior Member ajones's Avatar
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    Quote Originally Posted by scrandman
    So individually you have 384mb, but running SLI you'll only have 128mb!
    hehe! Actually, when you are running SLI, because the processing is being shared by the 2 processors you have 256mb of video memory, so you are not wasting as much as you think. Still a waste I agree, but then again couldn't you say that about SLI to begin with?

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    Banhammer in peace PeterB kalniel's Avatar
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    Individually you will have 256mb, as without SLI you are only using one card. In SLI you will have 256, but as all instructions will have to be duplicated, the usable space is only 128mb.

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    Quote Originally Posted by kalniel
    Individually you will have 256mb, as without SLI you are only using one card. In SLI you will have 256, but as all instructions will have to be duplicated, the usable space is only 128mb.
    And the usable space is exactly that - therefore in SLI mode you will have only 128mb. The other 128mb of redundant RAM would be as well as not being there!

    PS. For the 384mb - I didn't actually say anything about using them

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    Senior Member ajones's Avatar
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    I take it all back! ( ... except the bit that SLI is a waste of time.... :O)

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    mfr
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    Question SLI & != video memory

    Thanks a lot guys for your answers.

    Eventually, I went for a second 6600GT with 128mb.
    It's a way to raise the graphics power at quite a low cost.
    I'll probably make a big and expensive change next year.

    Ajones, just curiosity, but why do you think SLI is a waste of time ?
    Is it vs ATI crossfire, or multi GPU in general ?
    I would like to know your arguments, because from my perspective, the alternative would have been to throw my 6600 GT and buy a newer adapter. The cost would then have been higher than just buying a second 6600GT.

    mfr

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    Anthropomorphic Personification shaithis's Avatar
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    Its a waste because:

    You don't get double the performance
    Some games dont take advantage of SLI too well
    Some games just dont work at all with SLI enabled
    You cant have SLI and dual view enabled at the same time

    I would have sold the 6600 and bought a single card solution.
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    Jay
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    he will only have 128mb of video memory

    SLi work by loading the same data into each cards memory but each card accesses different parts of the data.

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    I'll be going single card next upgrade. Multi-GPU just isn't worth it.

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    Quote Originally Posted by Butcher
    I'll be going single card next upgrade. Multi-GPU just isn't worth it.
    Its worth it at high resolutions.

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    Banhammer in peace PeterB kalniel's Avatar
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    Quote Originally Posted by Boogle
    Its worth it at high resolutions.
    With 6600gt cards?

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    ALT0153™ Rob_B's Avatar
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    How much did the new card set you back?
    You could sell the 2 & buy a 7600GT (6600GTs are going for £50+ on ebay so more than enough for a 7600GT, maybe even get a 7900GS?!!)

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    Quote Originally Posted by Boogle
    Its worth it at high resolutions.
    I run 1920x1200 and it's still not worth it.

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