GMA 950 question

Discussion in 'MacBook Pro' started by LeftoverCrack, Feb 3, 2008.

  1. LeftoverCrack macrumors member

    Joined:
    Jan 2, 2008
    #1
    i was reading on the Apple forums about the GMA 950 and i saw a post saying..

    sure enough i looked at intel's website and it states the GMA having "256-bit graphics core running at 400MHz".

    is this all true?
     
  2. squeeks macrumors 68040

    squeeks

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    Florida
  3. LeftoverCrack thread starter macrumors member

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    Jan 2, 2008
    #3
    if the performance is actually that much better in windows and that osx actually restricts it to 64mb for some reason. i've just never heard of this, and why would Apple limit it like that?
     
  4. squeeks macrumors 68040

    squeeks

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    #4
    i guess its not going to really benefit from anymore than 64mb of ram
     
  5. elcid macrumors 6502

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    May 5, 2007
    #5
    to sharpen the line between the macbook and the MBP. besides memory only goes so far as it really only affects the resolution of the monitor.
     
  6. xraydoc macrumors demi-god

    xraydoc

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    #6
    ^^ not really...

    VRAM is used for two things - one is as a frame buffer for the image on-screen, and the other is as storage for 3D textures (since storing it on dedicated GPU RAM is faster than having to move the texture from system RAM to the GPU).

    The "integrated graphics" solutions, such as the GMA 950, GMA X3100 and several others that Apple doesn't use, lack their own VRAM and will instead share system RAM on an as-needed basis. Some of this RAM of course must always be reserved for video as the machine needs a frame buffer. Now, it is my understanding that on GMA 950 machines (Mac minis, gen 1 and 2 MacBooks and a specific educational model of the previous iMac generation), the chip reports to the OS/application that is has 64MB of VRAM. So this the application can count on should the rest of the RAM be used up by application code (or other background apps). Basically its so the application doesn't fill system RAM with 3D textures should the video chip report it as 2GB (i.e., system RAM amount) available instead of 64MB. If the application needs more, it'll swap it out with system RAM. But since its all system RAM anyway with the GMA 950, it doesn't really make a difference.

    Now, the Intel GMA X3100 that Apple uses in the current MacBooks has not only a faster GPU, but it reports to applications it has 144MB of VRAM. Is there a benefit in reporting more? Depends. If textures are swapped from system RAM to "VRAM" (which in this case is also system RAM), then no. If it needs to swap them from disk, then yes, it'll be faster, since more system RAM is pre-allocated. Though theoretically this leaves up to 80MB less free RAM (144MB - 64MB) available for everything else than the same app running on a GMA 950 solution.

    Now I may have gotten some of the technical details incorrect, and if I have please someone correct me. But for the most part, I believe the above to be more or less how it works.
     
  7. LeftoverCrack thread starter macrumors member

    Joined:
    Jan 2, 2008
    #7
    wow thanks.
    that was an excellent answer.
    but why does the intel website report the GMA 950 to have "Up to 224 MB maximum video memory"? what does this mean.. in extreme graphic intensive situations it will share upto 224? i'm afraid all this confuses me.
     

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