Dell UP2414Q (4k) mini-DP connection noise

Discussion in 'Mac mini' started by SirCochese, May 17, 2014.

  1. SirCochese macrumors newbie

    Joined:
    Mar 5, 2010
    #1
    Hello,

    I have a 2012 mini with a dell U2413T monitor connected over HDMI. I recently got a UP2414Q 4k monitor. I connected it using a mini-DP to mini-DP cable. OSX 10.9.2 defaulted the monitor to 4k resolution, but there was a lot of garbage on the monitor. It's hard to explain -- most of the screen is fine, but there's areas of the screen that have intermittent blocks of color. Then it'll go away. Then come back. There also some obvious texture garbage on the cursor as well. BTW, the garbage also isn't constant. It seems to hit random areas of the screen and also occasionally clear up for a second or two.

    I thought it might be due to the cable, but the garbage also occurs on the U2413T when the 4k is connected. I thought it might be due to multimon, but the same occurs if the 4k monitor is the only monitor. I thought it might be due to 4k, but the OS selected it and initialized it to 4k by default, so Apple thinks it should work. Finally, I upgraded to 10.9.3 for the HiDPI settings and it still persisted.

    I've attached some pics. Anyone seen this before? Any idea on a fix? I have AppleCare on the machine if an actual hardware problem is suspected.

    Thanks,
    SC

    ETA: If I leave all the connections alone, and just scale the 4k display to 1080p, the issue goes away. So it is somehow relevant that 4k is in use.
     

    Attached Files:

  2. FreakinEurekan macrumors 68040

    FreakinEurekan

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    Sep 8, 2011
    Location:
    Eureka Springs, Arkansas
    #2
  3. panzer06 macrumors 68030

    panzer06

    Joined:
    Sep 23, 2006
    Location:
    Kilrath
    #3
    I have a Dell 28 Monitor, P2815Q, 28" 4K monitor and it displays 2160p out of the box with no tweaks on 10.9.4 on a 2011 Mac Mini with AMD6630 using mDP to mDP cable. Text is crystal clear but menus are very very very tiny!

    However, mouse movement is sluggish and playing 4K video of any kind is beyond painful. Pauses, stuttering, etc. I'm told I can over-clock to AMD 6750 performance but outside of Windows I don't know how.

    I can scale down to 1080p and it works fine. I'll probably end up using it on my Windows machine but 4K does work -- sort of.
     
  4. kwijbo, Jul 25, 2014
    Last edited: Jul 25, 2014

    kwijbo macrumors regular

    Joined:
    Jan 28, 2012
    #4
    Unfortunately the HD 4000 graphics on your Mini don't support 4k resolution. See the Display and Audio Features Comparison section here:

    https://software.intel.com/en-us/articles/quick-reference-guide-to-intel-processor-graphics

    The Mini uses Thunderbolt 1, which sends video via Displayport 1.1. DP 1.1 has a data limit of 8.64 Gbps so while the connection to the monitor has enough bandwidth to support a 4k30Hz signal in theory, the limiting factor in this case is the HD 4000's connection max resolution of 2560x1600.

    If you were to set your resolution to 2560 x 1440 (same 16:9 ratio as your display) in Display Preferences I believe it should work, though when that signal gets to the monitor it will be upscaled to fit the native resolution and will look fuzzy.

    Now, if you want to experiment, since your monitor supports MST, you could try to connect both mDP and HDMI from the Mini to the monitor, set the monitor to DP 1.2 in the monitor's OSD menu and see what happens. I don't know if that will work but between those 2 connections there should be enough bandwidth to display an error free 4k picture but it will only be at 30 Hz.

    EDIT - You may also want to try to connect the 4k monitor using HDMI as the Mini supports HDMI 1.4, which supports 4k @ 30 Hz. Intel doesn't mention a resolution max for HDMI so its worth a shot.

    What's interesting in this situation is that the 6630M in theory has a display resolution max of something like 7,680 x 3,200 (I could be mistaken on the exact number) because the chipset supports Eyefinity, so the GPU output is not the limiting factor here, just the DP 1.1 connection, which is why you experience the sluggish performance. As mentioned above, the connection can only support 8.64 Gbps so you're being limited to a 30 Hz refresh rate.

    Similar to above, if you were to use both DP and HDMI simultaneously there is enough bandwidth to display at 60 Hz but no idea how it will work.
     
  5. panzer06, Jul 25, 2014
    Last edited: Jul 25, 2014

    panzer06 macrumors 68030

    panzer06

    Joined:
    Sep 23, 2006
    Location:
    Kilrath
    #5
    Excellent information! Setting the resolution to 1600p or 1440p does improve performance but of course means playing 2160p content is no longer viable, however, the mouse is better (not perfect) but the menus are much, much better and not as fuzzy as it was at 1080p.

    For now, I guess I'll need to just use my Windows laptop to play any 4K content. I can't afford a new Mac just yet!

    Cheers,
     
  6. kwijbo macrumors regular

    Joined:
    Jan 28, 2012
    #6
    Hopefully that sheds a little light on the situation. I'm curious to see if the dual connection method would work, mind giving it a try when you have a spare moment?
     
  7. panzer06 macrumors 68030

    panzer06

    Joined:
    Sep 23, 2006
    Location:
    Kilrath
    #7
    Interesting experiment. System thinks I have 2 monitors and lists them separately. The HDMI connection is limited to 1080p while the mDP is 2160p or 1440p (both at 30Hz).

    My windows laptop gets full 2160p over HDMI.

    Cheers,
     
  8. kwijbo macrumors regular

    Joined:
    Jan 28, 2012
    #8
    That's a positive sign - on your monitor, enter in the on-screen menu and see if Displayport 1.2 is enabled. If not, enable it and see what changes OS X sees. It may allow for full 4k. Also, I'm assuming you're on 10.9.3 or higher.
     
  9. panzer06, Jul 25, 2014
    Last edited: Jul 25, 2014

    panzer06 macrumors 68030

    panzer06

    Joined:
    Sep 23, 2006
    Location:
    Kilrath
    #9
    I am on 10.9.4 and when I enable DP 1.2 the screen goes blank and I can't access OS X at all. I have to change the input to HDMI and then I can get 1080p. I can then access the monitor menus to reset the display prefs which changes it to disable DP 1.2

    EDIT: Hmmm, looks like only late 2013 MBP 15 or any system with TB2 will support DP 1.2.

    Cheers,
     
  10. kwijbo macrumors regular

    Joined:
    Jan 28, 2012
    #10
    Ah, my mistake - I was thinking of Picture by Picture. That takes 2 separate sources and displays them on screen at the same time. The OP's monitor (UP2414Q) has it, I would assume yours does as well?
     

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