15" rMBP with dGPU memory management question

Discussion in 'MacBook Pro' started by evancg, Mar 19, 2014.

  1. evancg macrumors newbie

    Joined:
    Jul 11, 2010
    #1
    I'm debating between an Early and Late 2013 15" rMBP. I can get either one for around $1600 (open box late 2013, refurbished early 2013), which is my max budget. 8gb is enough for me, but with the Late 2013 (or Early 2013 on iGPU), I know the iGPU uses a portion of that (up to 1gb for the Iris Pro and 512mb for the HD4000, I believe?).

    My question is this: In those instances, if I force it to run on the dGPU, will that free up all the memory used by the iGPU, or does it still borrow some?

    Also, does anyone have any experience with the thermal impact in forcing the dGPU to operate in a non-graphic intensive situation (say, compiling something or editing audio)?

    The majority of my system intensive work (software development, audio\video editing, graphic design, or games) are done where I can plug in, so the battery impact of doing this isn't a big deal, but if the GT650m just naturally roasts the system in even light use, it would worry me.
     
  2. yjchua95 macrumors 604

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    Apr 23, 2011
    Location:
    GVA, KUL, MEL (current), ZQN
    #2
    If you're using the iGPU, system memory will be used. If you use the dGPU, it will not eat into your system memory.

    Depending on the situation, using the dGPU may enable the rMBP to run cooler because the processor doesn't have to work as hard, as tasks are sent off to the dGPU instead of the iGPU in the processor.
     
  3. theromz macrumors regular

    Joined:
    Aug 22, 2013
    #3
    But the dGPU will also increase the heat inside the laptop, I'm not too sure how well the MBP handle it but my old windows laptop will ramp up right away when the GPU was turned on. Chipsets have moved on since then and this could be a thing of the past but I would suspect the TDP of the case as a whole would rise when your dGPU is turn on having a knock on effect too the CPU.
     
  4. yjchua95 macrumors 604

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    #4
    It's a different story on rMBPs I suppose. When using VMware, my rMBP runs cooler on the dGPU than on the iGPU.
     
  5. leman macrumors 604

    Joined:
    Oct 14, 2008
    #5
    The graphics subsystem will take away from your RAM, no matter which GPU is active. Whether RAM utilisation is higher with the dGPU or iGPU - no idea, but I doubt there is much difference. AFAIK, the 'reserved' RAM is always reserved, even if you force the dGPU to be always active. The dGPU does not use much power when in idle mode, but it is still substantially higher than the iGPU usage. This will surely not 'roast' your laptop, but the battery life will be severely reduced.

    Why would you want to force the dGPU in the first place?
     
  6. evancg thread starter macrumors newbie

    Joined:
    Jul 11, 2010
    #6
    I would only force it if it turned out that doing so could force the iGPU to not use any memory, effectively freeing up 512mb of ram for system use.

    If it turns out the system reserves the iGPU memory regardless of whether it's going to be used or not, then I wouldn't force it.
     

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