New LG 38UC99-W compatibility with Macbook Pro?

Discussion in 'MacBook Pro' started by DrtyHarry, Sep 15, 2016.


Is $1499 a bit much for this display, or am I better off with the 27" Dell 5K?

  1. Get this 38" 4K LG display, it's worth it.

    44 vote(s)
  2. Get the 27" 5K Dell display, it's a better value.

    24 vote(s)
  1. 3587 macrumors 6502a

    Mar 23, 2008
    Well, that's good... But not. I know this monitor struggles when you plug/unplug the Mac from it... I'll get a purple screen sometimes...
  2. Hoondy macrumors newbie


    Dec 15, 2016
    general>quick charge?

    AMD freesync is a tech built into the video card i Ielieve, you need supported AMD card

    Attached Files:

  3. 3587 macrumors 6502a

    Mar 23, 2008
    USB Quick Charge is to quick charge mobile devices, such as an iPhone... It does not charge the 15" MBP.

    I guess I'll look into the MBP's AMD card to see if it is compatible.
  4. Fabiana macrumors newbie

    Dec 18, 2016

    I'm after a new display for my Mac Mini 2014. My first choice would be 4K or 5K, but the integrated graphics wouldn't allow me 60Hz. Perhaps 40Hz with some luck and TB2 to MiniDP cable, but still headache inducing...

    My second choice would be connecting the TB2 port to a PCIe case, allowing for a dedicated vídeo card. But then compatibility issues are very likely to arise in OS X and I'm not too sure I can get it to run stable. Not to mention cost...

    Then I saw the 38-inch monitor discussed here. I guess I'm not the only one who would love to see the little machine run that gigantic monitor. I just wonder if the IGP will handle it at 60Hz... Perhaps someone knows?
  5. 3587 macrumors 6502a

    Mar 23, 2008
    Time to upgrade the Mini if you're looking at a $1500 monitor :)

    It will take a lot to run this thing... I doubt that Mini would cut it.
  6. suleman_kh macrumors member

    Dec 3, 2016
    I've got 3 of these U2415 with Daisy Chain and works pretty good. Not tested with new MBP though, but will do, waiting for my DP > USB-C cable within this week :)
  7. 3587 macrumors 6502a

    Mar 23, 2008
  8. 3587 macrumors 6502a

    Mar 23, 2008
    Anyone else having issues with this monitor not recognizing the MBP sometimes? Often times I have to plug/unplug it numerous times before the screen comes up... Very frustrating and annoying! Is it user error?
  9. goobot, Dec 29, 2016
    Last edited: Dec 29, 2016

    goobot macrumors 603


    Jun 26, 2009
    long island NY
    So as far as I can tell from this thread, this monitor charges the 13 inch pro but not the 15, even not at a slower rate?
  10. 3587 macrumors 6502a

    Mar 23, 2008
    That is correct.
  11. Kiddomac macrumors newbie

    Jan 3, 2017
    Just wanted to chime in here, as I've finally received my 13 " Macbook Pro late 2016 and have had the 38uc99 for some time (used it on my PC with no problems using displayport with both 60 and 75 Hz fyi)

    Today I had lots of trouble with intermittend black screens and flickering using the LG supplied USB-C cable. I was very unhappy to say the least. A display port cable is no use for me, since I want to keep using my PC also.

    Disabling Displayport 1.2 in the OSM of the Display made for a stable picture, but online with 30 Hz.

    Right now I have a stable Picture in full resolution with 60 Hz using the LG supplied USB-C cable and I think the reason is, that I have also plugged in the charger to the macbook. I have to experiment more tomorrow to confirm this, but this seems to have done the trick. I guess the charging makes the connection a bit flacky.

    I know this is not a very technical description, but i hope it helps some people here. This whole thread has been very informative and assuring for me, knowing other people are also looking into this.

    Thanks guys.
  12. 3587 macrumors 6502a

    Mar 23, 2008
    Yeah, as great as this monitor is, it still does struggle with providing a picture once that cable is connected. It can be rather frustrating at times.
  13. nikster0029 macrumors 6502a


    Jul 21, 2010
    Thanks for the update! I believe that should be expected since a cable can only do so much! Look at how how 100W USB C charge cables cannot do data for example. Even the display cannot charge the computer anyway
  14. lockhartmacrumors macrumors newbie

    Dec 17, 2016
    Except, it doesn't struggle *at all* with Windows 10 on my MacBook Pro 13"....just the Mac side. Sleep and wake work just fine. I don't think it is a USB-C cable with power etc.'s how Mac OS communicates versus how Windows does...with the latter (surprisingly) being just fine.
  15. Grolubao macrumors 65816


    Dec 23, 2008
    London, UK
    Omg... the ppi in that screen must be horrible. I'm a ppi junkie and I think upgrading the screen is only if the ppi is better
  16. 3587 macrumors 6502a

    Mar 23, 2008
    Hopefully the NEXT update will cure the issues with macOS and this monitor... Lord Apple sure has been struggling... All my stuff is pretty buggy these days... Right now I'm having issues with the AppleTV displaying content. Never ends with Apple. Still love their products though!
    --- Post Merged, Jan 4, 2017 ---
    Yeah, the PPI is pretty terrible on this monitor when compared to the LG 5K.
  17. lockhartmacrumors macrumors newbie

    Dec 17, 2016
    Just an update, I think the problems on the Mac side are decidedly related to how it manages getting power and other signals over the same USB-C wire. Also, there's something going on with DisplayPort 1.2 being enabled or Disabled. When attached with just the USB-C cord, I can switch the monitor between Enabling DisplayPort 1.2 and Disabling, and it'll show the Mac screen when "Disabled" and not show a screen with "Enabled." All the while, the Mac thinks the screen is working. When disabled, though, I only get 30fps on the monitor using testUFO, not 60... so that is way suboptimal.

    Here's how I've solved this for my own needs, which is to have my MacBook Pro be *closed* yet still sleep/wake and have the monitor work at 60 fps:

    a. Attach laptop to monitor using USB-C, and *also* direct to power. Use an Apple Bluetooth mouse.
    b. Start cold, turn on MacBook Pro and when it has loaded, turn on Monitor with USB-C cable attached. This gets me 60 fps.
    c. I've installed software that doesn't allow the Mac to sleep... which apparently doesn't stop it from sleeping when the clamshell is closed...
    d. Close clamshell. Still get 60fps.
    e. When I want to leave the computer, I turn the monitor off using the monitor's controls. The MacBook sleeps.
    f. To turn the system on, first turn on the monitor, then click the MacBook to life using only the bluetooth mouse. Every time, now, that has worked, and I type in my password and everything is as I left it.

    If I attached some other USB mouse, it doesn't work...not sure why, but again I think MacOS is having issues working with various signals coming over that USB-C cable or through other USB connections. Not the Windows side, however, which continues to work perfectly.

    So, there's the current state of play...I can get it to work consistently and wake from sleep, but only if I put it to sleep using the monitor and wake it using a bluetooth mouse. Crazy that I had to go to such lengths and experimentation...
  18. 3587 macrumors 6502a

    Mar 23, 2008
    Yikes. It's frustrating to say the least. I'll try the monitor on/off trick. This sucks.
  19. RivalR macrumors newbie

    Jan 13, 2017
    As a new owner of the 38UC99 and a 15" model with the 460 graphics chip I've encountered very similar problems using the laptop in clamshell mode:

    Having both the power cable and the display connected over USB-C there is a very high chance the machine will crash when trying to wake it from sleep. On wake the display will light up shortly and then notify me of no incoming signals. Then, when I open the laptop the display will remain black (sometimes with the backlight on). I can only resort to a hard reboot or leaving it awake for a couple of minutes, usually it will reboot itself yielding a kernel panic report and a gpuRestart report as a result. When this happens I also have to disconnect/connect the usb-c cable for a couple of times, because the laptop will regularly just stop detecting the display.

    I've contacted Apple care and tried the following:
    • Test sleep/wake behaviour without an external display connected
    • Test sleep/wake behaviour with the external display connected in clamshell mode while booted up in safe-mode
    In both scenario's sleep / wake works without error, the behaviour during the wake process is also much more stable independent of the amount of time spent sleeping. I've read somewhere that during safe-mode a generic graphics driver is loaded which points at faulty AMD drivers in mac os sierra.

    I've also tested the following scenario:
    • Disable automatic graphics switching
    • Enable sleep prevention when the display is turned off
    • Only put the display to sleep completely circumventing mac os sleep (the machine always stays on)
    Problems occur less frequently but even in this scenario I've found that the machine sometimes errors out when having to wake the display with similar symptoms as described above.

    I am currently awaiting word from Apple care, keep you posted.
  20. lockhartmacrumors macrumors newbie

    Dec 17, 2016
    Great, thanks. I am convinced this is a software issue on the Mac OS/driver side, and not a firmware issue with the screen or something about the nature of the how it is set up to use USB-C. My 'solution' has been working consistently, so I'm assuming that eventually Apple will work it out. I'd think LG would be all over this, since this is really a terrific screen and has allowed me to completely clear up my desk and still have the real estate of two 24" monitors.
  21. 3587 macrumors 6502a

    Mar 23, 2008
    Yup - Same issues... But like the guy below this post says... That has been working for me as well... macOS is struggling with this monitor. I've never had my 16' MBP crash though...
  22. nikster0029 macrumors 6502a


    Jul 21, 2010
    I have the same issues with my other LG monitor too
  23. solamar macrumors regular

    Dec 30, 2008
    I do not think you can have both the USB-C port AND the display port used at the same time. If you use the USB-C, thats also doubling as a display port witch is shared with the actual display port. This might be the reason for your issues if you have DP plugged in with your PC and the USB-C to the MBP at the same time.

    This is a Either / Or situation.

    I know this is the case with Thunderbolt 2 on the 34UM88 and 34UM95, since the TB2 port also doubles as a display port and you cannot have them both plugged in at the same time.
  24. 3587 macrumors 6502a

    Mar 23, 2008
    The only cables I have running from the back of my monitor to my MBP is the power cable and USB-C cable. That is it.
  25. goobot macrumors 603


    Jun 26, 2009
    long island NY
    Bigger the screen the less ppi. This has the same ppi as a 40 inch 4k tv.

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