2018 MBP w/LG 27UD88-W 4K Monitor - 30Hz only

[ascender]

I've got a new MBP connected to the LG 27UD88-W over USB-C, but I can only output at 30Hz, with very limited resolutions, no scaling.

If I turn off DisplayPort in the monitor settings and turn it back on, the full set of options appear under System Preferences and I can select any of the usual resolutions at 60Hz. If the laptop goes to sleep, the screen wakes up back in 30Hz.

I've tried different USB-C cables, have flashed the firmware on the monitor but no joy.

Any ideas what else I could try?

Thanks,


Mike.

 

[doitdada]

I've had mixed success with my MBP 2018, and also MBP 2016, and my Dell UP3216Q. Same problem, but I've found an adapter that works. I've gone through 5 or 6 adapters before I found this. Apple have also limited the support for a wide range of USB-C cables, and even adapters that has support for 4 lane DP and 4K 60hz won't work on macOS and MBP 2016-2018 even though they may work with PCs.

CAC-1507 The Club 3D is a USB Type C to DisplayPort™ Adapter and is the easiest solution for connecting your USB 3.1 Type C source device featuring DisplayPort™ Alternate Mode to a DisplayPort™ 1.2 enabled (Ultra) High Definition Monitor, Television or Projector.

 

[ascender]

Thanks for the info. I did wonder if the answer was to go to DisplayPort, but it seems like a backward step given what usb-c can do over a single cable.

I've ordered an adapter so will see if that helps.

I also wonder if Mojave will make anything better when it comes to compatibility between all these different adapters & cables.

 

[BeatCrazy]

Even though you tried different USB-C cables, I still have to think the cable is the issue.

Heck, I once had my 2016 12" MacBook pushing 4K @ 60Hz no problem on the 27UD88.

 

[ascender]

So, with a usb-c to DisplayPort cable the monitor works perfectly. Four different usb-c cables don't work.

Its not too bad, I've ended up with two cables from the laptop instead of one, but that setup still lets me use the speakers and usb peripherals connected via the monitor.