Cannot get 4k@60Hz on 2018 MBPr

[Glems]

Hi,


I have bought a 4k / 60Hz display a couple weeks ago. I am using it with my Macbook Pro. I can get it running in 4k, but it is stuck to 30Hz which is quite frustrating.

My setup :

• My Mac : Macbook Pro retina 13" w/ touchbar 2018, Mojave 10.14.1
• Screen : LG UD59 LG USA | LG 27UD59-B: 4K UHD IPS LED Monitor (27 Diagonal)
• USB-C to DisplayPort : https://www.amazon.com/gp/product/B075V27G2R/ref=oh_aui_detailpage_o00_s00?ie=UT F8&psc=1
• I have also tried a USB-C to HDMI 2.0 cable, same results (same brand as the other cable)
  

Is this normal? Is there anything I could do to get 60Hz?


Thanks!

 

[apb87]

Try holding "option" while clicking the displays button. That should enable more resolution and refresh rate options.

 

[Kaani]

Check if there's difference with left and right side ports like I do.
Also check this thread:
https://forums.macrumors.com/thread...n-left-usb-c-ports-but-not-the-right.2158346/

 

[CrysisDeu]

I am quite sure HDMI will not work, but DP should work though. I am using uk850 and dp works.

 

[cynics]

Find in your monitor settings something called "HDMI UHD colors" "HDMI Ultra deep colors" or something similar to that maybe even "HDMI HDR color". Its typically an option that is enabled/disabled on an HDMI port to port basis.

This setting is defaulted off for compatibility and only applies to HDMI. But basically 4k60hz w/ 10 bit color exceeds the default bandwidth limitations so you need to tell the monitor what the input is.

See if that helps.

EDIT: did some digging on LG's site, called it with the HDMI Ultra Deep Colors"! Lol....

Note the very last option. Once it detects it you shouldn't even need to set it, it will use the 60hz refresh rate. My Samsung TV was the same way "HDMI UHD Colors"

 

[Glems]

Hello!

First I would like to thank you all for your relevant answers and apologize for not doing any follow-ups.

So it turns out that shortly after posting my first message I was able to somehow get 60Hz. I can't tell what was different. It did not last long unfortunately, and I am stuck at 30Hz.

About the ports : very interesting thread, thank you for this. I mostly use the ports on the left of the computer as my monitor is on the right. I have tried the ports on the right but still the same issue.

@cynics : I have looked for such an option in my monitor settings, but I did not find anything that would match. However, in my system information panel, I can see "Framebuffer Depth: 30-Bit Colour (ARGB2101010)", does that sound related?
[doublepost=1549977410][/doublepost]Edit : My bad, I have found it in the settings, and it is on. Looks like the monitor is not working when it is off.
[doublepost=1549977604][/doublepost]Edit 2 : while plugging/unplugging stuff and a few reboots, I have 60Hz now using the DP cable and a port on the left side, the bottom one. I am very confused but I will enjoy this moment having a monitor working smoothly. I am pretty sure it won't last

 

[1096bimu]

Hello!

First I would like to thank you all for your relevant answers and apologize for not doing any follow-ups.

So it turns out that shortly after posting my first message I was able to somehow get 60Hz. I can't tell what was different. It did not last long unfortunately, and I am stuck at 30Hz.

About the ports : very interesting thread, thank you for this. I mostly use the ports on the left of the computer as my monitor is on the right. I have tried the ports on the right but still the same issue.

@cynics : I have looked for such an option in my monitor settings, but I did not find anything that would match. However, in my system information panel, I can see "Framebuffer Depth: 30-Bit Colour (ARGB2101010)", does that sound related?
[doublepost=1549977410][/doublepost]Edit : My bad, I have found it in the settings, and it is on. Looks like the monitor is not working when it is off.
[doublepost=1549977604][/doublepost]Edit 2 : while plugging/unplugging stuff and a few reboots, I have 60Hz now using the DP cable and a port on the left side, the bottom one. I am very confused but I will enjoy this moment having a monitor working smoothly. I am pretty sure it won't last

This is most likely an issue with the quality of the cable, remember that it's not just a cable, Type-C to DP requires an active chip, and the quality of the chip will affect your results.

Unfortunately using 4k@60 with type-c will not be a cheap endeavour as it requires a different newer protocol than 4k@30, which is probably why even Apple doesn't sell you such an adapter. I recommend either you get a display that just has type-C input, or a thunderbolt-3 dock to ensure compatibility.

Also no, 4k@60 video output only does not use the TB3 protocol, so it's not the same thing.

 

[Glems]

So it seems like I can consistently get 60Hz using TB3/DP cable + the ports on the left side. I have occasionally screen flickering which is a bit annoying. I guess that it comes from the cable I am using (https://www.amazon.com/gp/product/B075V27G2R/ref=oh_aui_detailpage_o00_s00?ie=UT F8&psc=1). I'll try to get another one or a dock, but that looks a bit pricy. And ultimately I'll drop by at an Apple store, I also have keyboard issues for the second time...

Thanks again!