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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
 

FatalFallacy

macrumors member
Jun 12, 2013
59
24
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.
 

noratio

macrumors newbie
May 25, 2014
12
1
Does not give me the ability to force 60Hz at 4K

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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FatalFallacy

macrumors member
Jun 12, 2013
59
24
some people had success with zapping the NVRAM when the upgrade from Sierra to HS did the same to their systems last year.
 

schwartzki

macrumors member
Original poster
Jul 6, 2008
42
9
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.
 

ap58

macrumors newbie
Oct 19, 2018
1
0
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

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.
 

giffut

macrumors 6502
Apr 28, 2003
473
158
Germany
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.
 

speedfreak007

macrumors member
May 22, 2009
56
0
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.

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
 

schwartzki

macrumors member
Original poster
Jul 6, 2008
42
9
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
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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