IrisPro vs. GT750M for driving external display

Discussion in 'MacBook Pro' started by empireofpassion, Dec 15, 2013.

  1. empireofpassion, Dec 15, 2013
    Last edited: Dec 15, 2013

    empireofpassion macrumors newbie

    Nov 13, 2013
    Hi everyone,

    I am going to buy a rMBP after long analysis of the models and my needs/preferences. I finally made up my mind for a 15", being fully aware of the risk of having a yellow tint affected screen. I am hesitating between the 15" base model upgraded to 16GB and 512 GB SSD, and the high-end model. As everyone probably knows here, 100 USD, the dGPU and a slightly faster CPU are the only differences.

    My question is: does the dGPU provide any benefit when driving an external display, or does the IrisPro do the job as efficiently?

    I have no real need for the dGPU for the use cases discussed in threads about the benefits of the dGPU (no gaming at all, no CUDA etc.). I have read these threads. A recurring conclusion of these was: since the price difference is negligible and even 0 if the CPU of the 15" base model is also upgraded, and since the dGPU can be switched off with gfxCardStatus, it is a better deal to have the dGPU as it comes for free.

    However I have also read that the dGPU nevertheless fires up when connecting an external display and manual work is still required sometimes (like in this example) to control appropriately the dGPU via gfxCardStatus. I am afraid of these cases. I can accept the extra burden (closing all applications, configure again gfxCardStatus) if I know that the dGPU provides a real benefit when driving an external display. Hence my question: does the dGPU drive an external displays more efficiently than the IrisPro? If not I might then better go with the upgraded base model and not have any hassle controlling a dGPU I don't really need.

    Thank you for your feedback :)
  2. c1phr macrumors 6502

    Jan 8, 2011
    I don't think it would really matter. People can easily drive a Thunderbolt Display on an older and slower HD 3000, so the Iris Pro should be able to do it just fine.

    There is no way to force the integrated graphics with an external display if both GPUs are present, gfxCardStatus can't change that, since it has to do with the way the external display ports are wired. Though, if you're sitting at a desk with an external display, I would imagine that battery isn't an issue as you can just plug in the charger.
  3. empireofpassion thread starter macrumors newbie

    Nov 13, 2013
    Thanks, that is what I thought.

    Is a projector considered as an external display? In such situation it is sometimes less hassle to run on the battery (but OK a presentation will not last many hours and the battery should do).
  4. commac macrumors regular

    Nov 1, 2013
  5. Gav Mack macrumors 68020

    Gav Mack

    Jun 15, 2008
    Sagittarius A*
    If you are using the external display and just running 'standard' apps that will not tax any GPU the integrated only will be fine. You will also have to factor in future whether any of your apps may utilise Opencl more than CUDA as Apple are heading in that direction.

    Me personally I would pay the extra 100 bucks to have the faster CPU and the discrete just in case..
  6. thundersteele macrumors 68030

    Oct 19, 2011
    I'm writing this based on my experience with a 6750M in a 2011 MBP.

    1. An external screen always runs through the dGPU if such a dGPU is present in the system. In the past, if you blocked the dGPU using gfxcardstatus, and then connected an external screen, it would stay black.

    2. Whenever the dGPU is active the system produces more heat (i.e. idle temperatures going from 40s to 60s). This means that it is more likely that your fans come on, i.e. more noise. I find this particularly annoying with Skype or other video call software. My wife always makes fun of me because her MBA rarely fires up the fans under comparable loads.

    I don't know if there are any advantages of the dGPU with external screens.

    PS: Since it was mentioned before: A projector will also be driven through the dGPU, and the extra fan noise could be quite annoying in an otherwise quiet seminar room. However I have to say that on my system this never was a problem for this particular task!
  7. Doward macrumors 6502a

    Feb 21, 2013
    Odd, my 2.5Ghz late 2011 with the HD6770M idles ~50C with the dGPU running an external 27" TB display.
  8. c1phr macrumors 6502

    Jan 8, 2011
    My 2010 with 330m hangs out around 50-60 when it's plugged into my external display as well, and the fans usually stay down until I do something intensive like try to play a game.
  9. commac macrumors regular

    Nov 1, 2013
    Dunno if its my imagination but it seems my fans kick into high gear when gaming on the iGPU but only emit a gentle hiss while using the dGPU.

    2.3/16/512 750M

    Still trying to justify keeping the dGPU tho as I don't game regularly and am disappointed in the 750M performance so far. Hoping drivers change things.

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