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limitação da gma950 em osx

Discussão em 'Apple Geral' iniciada por WackyMac, 22 de Fevereiro de 2007. (Respostas: 2; Visualizações: 870)

  1. WackyMac

    WackyMac Power Member

    Não sei se dúvidas persistem relativamente ao hipotético "capping" da gma950 em osx por software, mas cá vai uma explicação mais técnica:


    "I see a lot of speculation here regarding the GMA950 and that is has been "capped" at only 64MB by Apple.

    First a disclaimer: Although I work for Intel I am not a spokesperson for the company and my comments shouldn't be considered any sort of official company statement. During my day job I develop graphics drivers for Intel including the GMA950 series. However, I don't have any insight into Apple's device drivers. Similarly, everything included here is available from public sources and does not include any proprietary information.

    What Apple is saying (and makes complete sense based on the architecture of the chipset) is that they allocate a minimum of 80MB of system memory for the GMA950 to use. Additional memory will be allocated as needed up until the maximum addressable size which is 256MB.

    Put simply, there are two types of "things" that go into video memory:

    1) The frame buffers
    2) Textures/Surfaces

    The GMA950 has a maximum resolution of 2048x2048 pixels with 32bpp color depth. That means a single frame buffer can take up to 16MB.

    It can also display two unique images simultaneously. In the case of the Macbook, this means the internal LCD panel and the external DVI connector. Taking this into account we're up to 32MB -- in practice this will never happen since there really aren't any displays with that high a resolution on the market. However, Apple could be playing it safe and always reserve enough memory to handle all frame buffer sizes.

    Similarly, Apple may be using the concept of having front and back buffers to provide smooth video. This means each display effectively has two frame buffers associated with it. As a result, now we're up to the magic 64MB number.

    In addition to frame buffers, there are typically off-screen areas that are used to cache bitmaps, individual characters of fonts, the contents of a window that is going to be blitted or blended, etc.

    There are countless uses for off-screen memory. Importantly though, the GMA950 can only off load work from the CPU when it has this memory to use. It can only accelerate drawing and compositing within video memory.

    In this case, it sounds like Apple has ensured that there is a minimum of 16MB of off-screen memory for this use. As a result, we get the 80MB number.

    The important thing to realize about integrated graphics chips such as the GMA950 is that memory can be dynamically moved from the system to the video processor at will. This is done in 4KB chunks up to the maximum address space of 256MB.

    We already know from IOReg that Apple has configured the GMA950 with a 256MB aperture.

    And Apple themselves have effectively confirmed all of this with their knowledge base article:

    Mac mini (Early 2006), MacBook, iMac (Mid 2006): About the Graphics Processor ( http://docs.info.apple.com/article.html?artnum=303407 )

    In short, the 64MB number being thrown around is a minimum value not a maximum value."

    by drp

    peace, fiquem bem.

    ps:só agora reparei que o @aeon já tinha feito referência a este mesmo artigo num outro post.as minhas desculpas
    Última edição: 23 de Fevereiro de 2007
  2. eastern

    eastern Power Member

    A única dúvida que me surge é se o MacBook é capaz de renderizar imagens tridimensionais em programas específicos de modelação 3D, ou até mesmo no AotoCAD 3D com o Windows em BootCamp....
  3. WackyMac

    WackyMac Power Member

    Do que vi, posso-te dizer que a gma se porta bem no autocad, mesmo ao nível do 3d. Claro que a performance é inerente à complexidade do projecto, mas no geral pode-se dizer que aguenta.

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