GPU Question 5K iMac

Discussion in 'iMac' started by fob, Dec 1, 2015.

  1. fob macrumors member

    fob

    Joined:
    Sep 11, 2015
    #1
    Does the 5k iMac use its discrete graphics card for normal OS UI rendering or does it use the integrated graphics from intel to render UI and switch to dGPU on a required basis?

    i'm no gamer and would at most program some games in Xcode and run the simulator. Will m380 be sufficient?
     
  2. Laai macrumors member

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    Germany
    #2
    It uses solely the dGPU.
     
  3. maflynn Moderator

    maflynn

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    #3
    I was wondering this myself.
    so you're saying there's no way to switch to the iGPU?
     
  4. MrNomNoms macrumors 65816

    MrNomNoms

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    #4
    The concern I'd have is future proofing particularly if Apple is looking at offloading more of the UI onto the GPU and whether there is enough headroom left on the GPU considering that the M380 has less grunt than the M295X based on what I've read over at Notebook Check.
     
  5. Samuelsan2001 macrumors 603

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    Oct 24, 2013
    #5
    Why would you compare the high end from the last generation (with double the vRAM) with the low end of the new generation??? The comparison should be M380 with the R290.
     
  6. MrNomNoms macrumors 65816

    MrNomNoms

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    #6
    For one obvious reason; if the M295X struggles then I doubt that the M380 will fair much better - that is why.
     
  7. Samuelsan2001 macrumors 603

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    Oct 24, 2013
    #7
    But that still makes no attempt to answer their question which is wether the M380 is good enough for their use case....

    Now I admit that, with the very small amount of vague information the OP has given about their graphics usage, that is an almost impossible question to answer but your reply was really no help either. The OP has not indicated that they have used a 295X or that it wasn't powerful enough for their needs, indeed I imagine it would be vast overkill.

    OP I would recommend the M390 it is far more powerful than the M380 and will give you some room for future increases in how you use your GPU without spending out a huge amount on upgrading graphics. An extra $200 gets you a better graphics card and a fusion drive that is probably worth the money (although personally I'd also upgrade to a 2Tb fusion to get the 128GB SSD over the 24GB SSD cache in the 1TB fusion).

    To be honest though if an arm processor can run your graphics fine then almost any dGPU is more than enough, if you are developing huge graphics apps or games for macs then you may have an issue but if you were I don't think you'd be asking these sort of questions.

    This thread has some info on shaders and specs that may be of interest

    https://www.reddit.com/r/mac/comments/3opvhn/amd_radeon_r9_m380_with_2gb_vs_m390/

    And here is a direct comparisson albeit with double the RAM Apple provides.

    http://www.game-debate.com/gpu/inde...pare=radeon-r9-m390-4gb-vs-radeon-r9-m380-4gb
     
  8. Erdbeertorte macrumors demi-goddess

    Erdbeertorte

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    #8

    I think it's just to slow to drive the 5K screen. It's not even visible in the System Profiler:

    Bildschirmfoto 2015-12-01 um 14.40.52.png
     
  9. Laai macrumors member

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    Apr 23, 2012
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    #9
    Exactly. The option ist not available by default. Don't know if there is a way to hack your way into it, but by design the iMac uses only dGPU.
     
  10. maflynn Moderator

    maflynn

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    #10
    I think this answer is why.

    I forgot that the current Skylake iGPU is pretty slow and there's a lot of pixels that need pushing on the 5k display. That's the reason why the 4k is still on Broadwell - it has a much better iGPU.
     
  11. redheeler macrumors 603

    redheeler

    Joined:
    Oct 17, 2014
    #11
    Why would you need to? The reason laptops have this feature is to conserve battery life. Not a concern on desktops, and a 5K display driven by an iGPU can't be a pleasant experience.

    ------​
    The iGPU is not recognized on the late 2014 as well. As far as I know there is no way to switch to it.
     
  12. Laai macrumors member

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    Apr 23, 2012
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    #12
    Why would it?

    Other than consuming overall less energy, there are 0 advantages of using iGPU on a desktop machine.

    Switching GFX cards causes UI to twitch a little, iGPU is slower while dGPU can easily render all images with steady framerate, dGPU can take off workload from apps that support it, the machine would not be quieter since the fans minimal speed would have to be tied to dGPU temp (otherwise at every switching the fans would speed up in order to keep dGPU cool and it would be annoying).

    Using dGPU as a single solution is easy, Apple can market it easier and on a desktop machine there are no (major) power concerns.
     

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