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Mojave Broke 4K/60Hz on 2017 rMBP13

S

schwartzki

macrumors member
Original poster
Jul 6, 2008
42
9
Have a Cable Matters USB-C to HDMI 2.0 cable that was working perfectly with my 28" Samsung 4K monitor. Was working @ 60Hz with High Sierra but upon the update to Mojave the monitor is now back to 30Hz. I have submitted a bug to the feedback app back in early August but it is still not resolved.

Any one else have this issue?
Is there is a work around or is there a new cable that works. Thanks
 
You could give SwitchResX a chance from madrau.com, it's try before you buy.
Helped me out several times when dealing with adapters and monitors, allowing you to set up custom resolutions&settings and squishing the most out of the available ports' bandwiths.
 
schwartzki said:
Does not give me the ability to force 60Hz at 4K
Click to expand...

Same problem here! Updated to Mojave and it breaks 4K 60hz. I am using a Mini Display (Thunderbolt) adapter to HDMI 2.0 60hz from Club that I have been using for 2 years now on my iMac 5k.

I have tried to create my own EDID, no luck. My UHD TV is detected as a TV and won't give you the ability to change the refresh rate. So so bad. If I use bootcamp and boot into Windows, same iMac, same cable, same adapter, everything works just fine in 4K at 60hz. So really a software bug.

P.S. I also have a Accell adapter.. same problem with two adapters that can do 60hz at 4K..
[doublepost=1539195758][/doublepost]Made more progress.

I can confirm that forcing 60hz using SwitchResX is working, but can't use scaling. Still can't get 4:4:4 to work. YUV(compress data color) is in use still with SwitchResX.

NO WAY I'll pay for to get the resolution that I am supposed to have right out of the box.

Grrrrr Apple.. Steve Jobs must be turning is in tomb. When I renew it won't be Apple. I am totally fade out. Windows does it all now with color gamut, HDR and Dolby Vision / Atmos. Can't deal with a company that keep billions and to develop on the latest technology and sell overprice computer with a CPU that is always a generation behind.... come on..
 
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some people had success with zapping the NVRAM when the upgrade from Sierra to HS did the same to their systems last year.
 
I did some troubleshooting with AppleCare T2 today. NVRAM/SMC reset. Bootcamp Win 10 also failed to push 60Hz. So they are sending a USBC to Displayport adapter to test with. Guessing the Mojave broke support for the cable I was using.
 
schwartzki said:
Have a Cable Matters USB-C to HDMI 2.0 cable that was working perfectly with my 28" Samsung 4K monitor. Was working @ 60Hz with High Sierra but upon the update to Mojave the monitor is now back to 30Hz. I have submitted a bug to the feedback app back in early August but it is still not resolved.

Any one else have this issue?
Is there is a work around or is there a new cable that works. Thanks
Click to expand...

I use a Dell 24" 4K monitor and have a similar problem. At work I use a usb-c to DP cable, at home I use a usb-c to mDP adapter. Same behaviour in both cases. Most;y it displays at 30Hz but occasionally will run at 60Hz. Haven't discerned any pattern to the behaviour.
 
This looks like a distinct pattern and intend in recent years, disabling third party hardware adapters with each new macOS version.

Keep in mind that Apples implementation of USB-C regarding interoperablity is average at best.
 
giffut said:
This looks like a distinct pattern and intend in recent years, disabling third party hardware adapters with each new macOS version.

Keep in mind that Apples implementation of USB-C regarding interoperablity is average at best.
Click to expand...

Is there any news on this issue? I'm having it as well and I really hate is as my 4k TV is now unusable
 
speedfreak007 said:
Is there any news on this issue? I'm having it as well and I really hate is as my 4k TV is now unusable
Click to expand...
I had to buy the Moshi USB-C to Displayport cable on the Apple Website in order to get my 4K @60Hz to work again. There might be other options but AppleCare Level 2 techs couldn't figure it out and we spent a few days and resets/tweaks to try to get it to work again.
 
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