iMac 5K + Second/Third display?

Discussion in 'iMac' started by supercooled, Apr 11, 2015.

  1. supercooled macrumors 6502a

    Sep 6, 2007

    I've been having a lot of issues with the current monitors at my disposal.

    They are:

    Seiki SEUY04 39" 4K
    Dell 3008
    Dell P2815Q 4K

    Here's the thing. I can't stand running the Dell 3008 in the summer because of how hot it gets so that's not even an option right now. I tried running the Dell and Seiki with a new DP > HDMI cable I just bought thinking the included one from the Dell was faulty but the iMac refuses to run it at anything higher than 1080p. I cannot for the life of me figure out why anything higher simply shows a black screen.

    I have the i7/295R combo with 32GB of memory. Recently updated Yosemite to 10.10.3.

    Even my 2014 runs the Seiki / Dell @ 4K fine with a little lag but the iMac just refuses to show anything on the screen.

    Any success stories would be uplifting; at least I know the issue may be a fix or two away.

  2. edjrwinnt, Apr 11, 2015
    Last edited: Apr 11, 2015

    edjrwinnt macrumors member

    Mar 8, 2008
    North Ridgeville, Ohio
    I use 4 lcd's on my retina iMac but of the 4 only one is a 4k one. I have 2 connected via thunderbolt and 2 via usb. I have the 290 video card, and now that I have 10.10.3 I have no lagg at all with anything including mission control.

    To my understanding you can only connect one additional 4 k monitor to the retina iMac.
  3. supercooled thread starter macrumors 6502a

    Sep 6, 2007
    Well, I'm testing one monitor at a time and none of them seem to work past the 1080p resolution. I'm running into a problem with the Dell especially where it keeps connecting and reconnecting and how I know this is in SwitchResX, the Dell appears in the detected monitor, then disappears and reappears over, and over and over, ad nauseum. This may be a problem with SRX but I doubt it. More likely the Dell itself which was flakey at best with connected to my Mac Pro. Still doesn't explain why it works fine on my Mac Mini and Mac Pro same for the Seiki. The Seiki paired with the Mac Mini is actually bullet proof. Works great on that little guy.

    I refuse to believe it is the iMac though because I just spent a small fortune on this and it's not behaving.

    Can you elaborate on how you connect your monitors to the iMac? Which brand of cables?

    This is what I ordered.

    May be I"m paying for my sins for cheaping out.

    EDIT: I didn't realize USB can send video signal.
  4. edjrwinnt macrumors member

    Mar 8, 2008
    North Ridgeville, Ohio
    I just realized my 4K Dell is the same as yours; model P2815Q. I'm using a generic mini display port connector on both ends with my iMac retina thunderbolt connection. I can crank the rez all the way up to 4k with no problem. Almost all of my cables are from

    I'm using two Mygica USB 2.0 to HDMI DVI VGA 1080P DisplayLink Adapters with DisplayLink software. Up until the latest driver update from DisplayLink last month, it was a pain in the butt rearranging all of my monitors the way I want them after each reboot. With the latest DisplayLink driver update I no longer have to adjust them and their positions are remembered.

    By the way, the only thing I don't like about our Dell 4K monitor now is the mouse drag. I hated using this Dell 4K on Windoze 7 because the scaling was horrible.
  5. supercooled, Apr 11, 2015
    Last edited: Apr 11, 2015

    supercooled thread starter macrumors 6502a

    Sep 6, 2007
    I have no issues getting 1080p to work but I want to get 4K going on my Seiki which looks like turd on anything less than 4K from 2 feet away from my face. Likewise, the Dell is very soft at anything below UHD.

    Can you link me to the adapter on Monoprice? I have bought from them in the past but their myriad of cable selection is enough to make me dizzy.

    I have also come across a lot of postings on Dell Community board that say Apple's TB to DP transfer is very touch and go so I am kind of relieved. They do recommend a Thunderbolt to Display port adapter of some kind then carry the rest of the signal via whatever cable you want.

    Also since you have the same monitor, did you encounter any funkiness with the included cable? It doesn't seem to work on queue sometimes.

    I'll likely be ordering this adapter to see if I can get it to work.

    Buying cables/adapters to make Macs play nice seems to be the trend lately. Damn these different standards. Sigh.
  6. edjrwinnt macrumors member

    Mar 8, 2008
    North Ridgeville, Ohio
    Personally I try to avoid adapters if I can. I had a hdmi/displayport adapter recently that went flaky on me and I had to replace it. Can't you just use a straight cable (no adapter) with what exactly you need on each end? Monoprice is so cheap I usually will try different combinations of cables and adapters to see what works.

    If you search on the monoprice website for a specific connection type it breaks adapters and cables that match down pretty well in the search results.

    These low end monitors are flaky with their cable connections. I always thought it didn't matter given they are digital (0's and 1' versus analog sound) but it does.


    I don't think the Seiki is meant to be used a computer monitor either. TV monitors are best viewed from a distance.
  7. xmichaelp macrumors 68000


    Jul 10, 2012
    You have 4 monitors connected to your base GPU retina iMac with no lag? Wow.
  8. JeffyTheQuik macrumors 68020


    Aug 27, 2014
    Charleston, SC and Everett, WA
    I have 2 4K monitors running at 3840x2160 at 60 Hz from both TB ports on my 2014 Retina iMac.

    The GPU is sweating, as when I run X-Plane on it, I have to step down to 2560x1440 on all 3 screens to get anything above15 fps. I'm flying a Cessna, not an SR-71 at 10 feet off the ground.

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7 April 11, 2015