dGPU needed for external monitors?

Discussion in 'MacBook Pro' started by MovieGuy34, Nov 11, 2013.

  1. MovieGuy34 macrumors member

    Aug 2, 2013
    Hello all

    I have the new 15 inch 2.3 dGPU rMBP. I use it at work and I connect it to a 21inch Gateway monitor via HDMI. According to graphic card status it says it's turned on the dGPU. Is it really necessary to have this running? Shouldn't the Iris Pro be powerful enough to power a monitor?

  2. dukebound85 macrumors P6


    Jul 17, 2005
    5045 feet above sea level
    my 13in mbp that only has an igu can run external monitors just fine
  3. MovieGuy34 thread starter macrumors member

    Aug 2, 2013
    Yeah my 2008 macbook used to run it no problem. I'm just surprised to see this new one automatically switching to it. Was just wondering if anyone knew of any reasons why it might need to be on. It's not really a big deal. I keep the computer plugged in pretty much all day.
  4. c1phr macrumors 6502

    Jan 8, 2011
  5. dusk007 macrumors 68040


    Dec 5, 2009
    The problem is Apple ONLY wired the dGPU to the external video ports. The internal screen is wired to a mux chip that switches the input. That mux chip is connected to both GPUs.
    The alternative would be a very complex logicboard with lots more muxing hardware for all the ports. Or Apple could switch to the IMO vastly superior software based graphics switching (like Optimus from Nvidia or Enduro from AMD). In the latter only the integrated GPU is directly connected to the output ports and the dedicated GPU only supplies processing power when needed but lets the integrated handle the display output.

    Apple does neither so you have to use the dGPU even if all you do is show still images like slides on a projector for some presentation while you talk.

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