Does using dGPU free up system memory?

Discussion in 'MacBook Pro' started by johngwheeler, Nov 19, 2014.

  1. johngwheeler macrumors 6502

    Dec 30, 2010
    I come from a land down-under...
    I understand that the integrated Iris Pro GPU uses system RAM (up to 1.5GB, I think). If you force the machine to use the dGPU (via software, using an external monitor or running Windows in Bootcamp), does this then free-up the RAM that would have been used by the Iris Pro?

    Or does this video RAM stay in some "reserved" space irrespective of dGPU use?
  2. leman macrumors G3

    Oct 14, 2008
    The video drivers would usually hold a copy of the textures and other data in the system RAM, so I doubt that there are significant space savings. If course, it depends on the driver and the way the OS interacts with it.
  3. poiihy macrumors 68020


    Aug 22, 2014
    I don't think it would put it away, otherwise it would take a bit longer to switch to integrated.
  4. Freyqq macrumors 601

    Dec 13, 2004
    In OSX, it is designed to be able to switch back and forth immediately. So, I wouldn't be surprised if a full copy of everything in the dGPU vram is also in the system ram. It would be neat if the iGPU could work with the dGPU's vram, but I don't think that is the case. However, bootcamp disables the iGPU completely. Windows doesn't even know it exists. So, it wouldn't use any system ram at all.

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