Late 2015 iMac 5k + R9 395X + GTX980Ti eGPU

Discussion in 'iMac' started by mmomega, Feb 22, 2016.

  1. mmomega, Feb 22, 2016
    Last edited: Feb 22, 2016

    mmomega macrumors demi-god


    Dec 30, 2009
    DFW, TX
    I'll start by saying this project isn't for most folks but for those with a multi-monitor setup that want more powerful graphics it may be an option for you.

    Also, I'll add in, I don't really want a regular PC, don't want being the key words, and if I can get more performance out of my iMac then that's what I am going to do. I am aware there are more inexpensive ways of going about getting higher performance with certain parts but I am fortunate enough to be able to do this project and I am happy with the results.

    Ok, on to the meat n' potatoes of the project.

    My computer setup for the past few years has been a 27" iMac with 2 external 27" 1080p monitors. While this seemed to have worked for a while, I come to realize 3 - 27" monitors was a boatload of screen real-estate... resolution wise and physically on my desk.
    Which got me to thinking and researching. What if I cut down to 2 - 27" screens but beef up my video card if that's even possible or an option.

    I do a fair amount of video processing and would love the added benefit of real GPU processing power.

    I had already ordered:
    late 2015 5k iMac
    i7 6700k CPU
    R9 395X GPU w/ 4GB RAM
    32GB 2133MHz Kingston Hyper X RAM
    512GB SSD

    then the researching of eGPU's started, which lead to ordering:
    Akitio Thunder 2 box
    EVGA GTX 980 Ti SC+ ACX2.0 w/ BP GPU
    Corsair CX750M PSU
    and a few extra pieces to complete the project
    2.5mm x 5mm Barrel Plug
    2 - 4pin female Molex connectors

    The result:
    Screen Shot 2016-02-22 at 9.25.04 AM.png
    Screen Shot 2016-02-22 at 9.29.46 AM.png
    Screen Shot 2016-02-22 at 9.34.06 AM.png
    Screen Shot 2016-02-22 at 10.50.53 AM.png

    So the reasoning I give that this project is better for those with multi-monitor setups is that the eGPU doesn't seem to be powering the internal iMac screen, I can't be sure but performance on it seems a tad sluggish. Not sluggish like a slide-show presentation but just slower than when the eGPU is not connected.
    Normal video watching like YouTube full screen or Netflix and Hulu seem fine and I have yet to actually check performance on the iMac screen, it just "feels" slower.
    It is also now locked at no higher than 4k resolution only when the eGPU is outputting to the 2nd monitor.
    If I disable video output from the eGPU the iMac goes back to 5k and I can still utilize the eGPU processing power for rendering projects.

    However, eGPU performance on the external monitor is quite, quite good. The only game I have installed in OS X currently is Warcraft. On the 1080p monitor, Ultra Settings and every option set to the highest available setting I was getting on average of 99fps.
    I have not done thorough testing of any sort yet other than a few benchmarking programs and Warcraft so these are the results as of now.

    In Windows 10 I got to run 3dMark but as of yet I had to leave before getting done with FireStrike so I will post those results later.

    3D Mark 11 = GPU Score of 19,343
    3D Mark Vantage = GPU Score of 53,759
    3D Mark 13/FireStrike = to be continued

    I will try and do more testing within Windows and OS X with results from both cards to show the difference the eGPU makes.

    I also do a little bit of Folding@Home for our Macrumors Team.
    And with the eGPU I was able to get my production up quite a bit.
    Now this I had to do from within Windows because for whatever reason F@H doesn't utilize GPU's on the Mac Client that I'm aware of.
    In just under 2 weeks I went from rank 249 to 60 or 360,000 points to 4.4 million points.
    There were days when I needed to work in OS X so I had to shut folding down but overall I am happy with how well the eGPU is working. For those interested in folding this may be something to look at.
    Screen Shot 2016-02-22 at 10.35.53 AM.png

    If anyone is interested or wants to see anything in particular in regards to pictures/specific benchmarks/etc please post below and I will do my best to get the results posted ASAP.
  2. jacko777 macrumors newbie

    Jan 20, 2016
    sorry, can the egpu performaning well on the imac5k screen? If yes, how is the performance compare with 395X?
  3. tdbrown75 macrumors member


    Apr 28, 2015
    Dallas, TX
  4. teethemagicbee macrumors newbie

    Jul 1, 2014
    Do you think the slight sluggishness is due to TB2 port? Possibly faster if the new one gets TB3?
  5. -BigMac- macrumors 65816


    Apr 15, 2011
    Melbourne, Australia
    can i have a photo of your finished project please
  6. Sirmausalot macrumors 6502a


    Sep 1, 2007
    The eGPU CANNOT power the main iMac screen and TB2 DOES NOT RUN THE GRAPHICS CARD AT FULL SPEED. That's just a warning for those that think they want to go this route for full powered graphics performance. However, I do commend the OP for this as it seems to work for him and gives us all useful information.
  7. mmomega, Feb 23, 2016
    Last edited: Feb 23, 2016

    mmomega thread starter macrumors demi-god


    Dec 30, 2009
    DFW, TX
    I'm not sure what the eGPU is powering at this moment, the only information I have is that the 980 Ti can output 4k and when it is connected my iMac screen resolution won't go higher than 4k. Also I have the R9395X disabled from device manager in Windows.
    If I re-enable the R9 card the iMac screen then gives me the options to set it back to 5k, so to me this is strange behavior if the eGPU is not having some effect on the internal display.
    Also when connected in OS X the screen can not be set to higher than 4k resolution, my options are 4k, 1440p, 1080.

    I have read another post recently where someone with a rMBP with discrete graphics was able to get Optimus working and the eGPU powers the internal display. His has a 750m dGPU and now a GTX970 eGPU.

    When I get some time I'll try booting into Windows without an external monitor to see if the eGPU is actually doing anything with the internal display.

    I also haven't come across anyone else with a late 2015 27" R9 machine that got their setup to work in Windows 10. Yet.
    --- Post Merged, Feb 23, 2016 ---
    it is far from finished at the moment and definitely not very elegant looking. I pretty much threw it together to test if it worked and that is how it has stayed for the last couple weeks. So at the moment the eGPU is just sitting out in the open on my desk with the PSU looking like some sort of Frankenstein project until I get more time to work on either fabricating/buying a new case or just hiding it somewhere in my desk that gets good air flow and only have the TB cables running to my iMac.

    I'll at least get a pic or two in a bit to post.
    --- Post Merged, Feb 23, 2016 ---


    the small fan on top of the gpu is the case fan from the Akitio. Setting it on top of the gpu to blow air down behind the card across the Akitio board has help quite a bit with temperatures.
    Prior to doing this the back of the eGPU casing got quite warm doing extensive GPU processing, I mean it did fine for over a week and I wasn't worried, I just wondered if placing that fan there would help and it has.
    The casing is much much cooler now and it barely warm to the touch and the GPU has been working for about 18 hrs at 80% gpu load. The GPU itself shows a reading of 68-70C like this and the card is barely audible. I can hear the GPU processing more so than the fans.
    --- Post Merged, Feb 23, 2016 ---
    Possibly, but I need to do some more testing just to be sure.
    I'm not even 100% positive that the eGPU is or how it is effecting the internal display at the moment.
    I was excited that everything was working that I didn't do a lot of testing different aspects of the setup, I just did some general benchmarks to check performance and kind of left it alone for the time being.

    TB3 would definitely speed things up and offer more bandwidth.
  8. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    As one of the people who did the initial work on the hack that allows screen output I can tell you for certain that in OSX the eGPU does NOT influence the internal screen.

    The actual hack discovered by Netkas that is at work here requires turning off the 5K ability to turn on the eGPU display output. It is that simple.

    I don't believe that anyone has shown an iMac using Optimus in WIndows, especially as the iMac in question uses an AMD card.

    Easy enough to find out, run a benchmark like 3D Mark or Uningine Valley. They know what GPU is being tested.

    Even something like OpenGl Viewer can tell you this basic info.
  9. mmomega thread starter macrumors demi-god


    Dec 30, 2009
    DFW, TX
    Right on. I'm fairly certain you're correct, I just haven't got around to even trying to run a benchmark on the iMac screen to see.
    It's on my list of to-do's. Thanks for the info.
  10. Adam552 macrumors 6502

    May 30, 2006
    Liverpool, UK.
  11. jacko777 macrumors newbie

    Jan 20, 2016
    I have an idea. Should we have that egpu connect to a 4K capture card to make use of the internal 5k display? Does it make sense?
  12. mmomega thread starter macrumors demi-god


    Dec 30, 2009
    DFW, TX
    Yes. In the OP I said it is working under Windows 10.
  13. Aigars macrumors newbie

    Feb 21, 2017
    I'm planning for similar project. I have Imac 5k 2014 with 4790k and 295x 4gb and 32gb corsair 1600mhz cl9. I don't need any external monitor, but what I want is better performance in Final cut and after effects. So do you feel any discomfort while working on internal screen with egpu attached? And do you feel a performance boost in rendering (final cut and after effects)? Your answer will be very helpful. Thank you in advance.

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