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caligules

macrumors newbie
Original poster
Jan 21, 2019
3
0
Hello, I attached a picture in this post with the details of my system. I just bought an LG 27UK850-W and I have serious performance problems. Even with the naked eye, it's pretty obvious when I perform quick moves. When I try to watch a YouTube video at 4K, it's stutters really really bad, it's unwatchable. I've connected the monitor via USB-C (the one that came with the monitor) and under Settings it's displayed 60Hz. I tried everything, I've searched online for solutions for two days now. Do you have any idea why I have this problem? It's just a hardware limitation from my Macbook (even if I read online that users have no problems running 4k even with older Macbooks) and I can't do nothing about it? Maybe a factory reset will work? That's pretty much my last resort. Also, I'm wondering if maybe it's the cable to blame. The thing is that when I watch a 4k Youtube Video, under Activity Monitor, the CPU is really stressed out.
 

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caligules

macrumors newbie
Original poster
Jan 21, 2019
3
0
I don't have another one besides the one included and the one from the charger. Should I buy another one, it's worth trying or it's a long shot?
 

LIVEFRMNYC

macrumors G3
Oct 27, 2009
8,876
10,982
I don't have another one besides the one included and the one from the charger. Should I buy another one, it's worth trying or it's a long shot?

I personally wouldn't do anything else until I confirm it's not the USB-C cable. So yes, you should get another cable, but it's not a guarantee, your issue can also be something else.

BTW .... have you tried the one from the charger?
 

Trey M

macrumors 6502a
Jul 25, 2011
964
334
USA
Yeah try another cable.

Also, go to About This Mac > System Report > Graphics/Displays and validate whether MacOS is reporting 60Hz or 30Hz. Odds are the issue you’re reporting is related to 30Hz.

Also Google as some of the LG monitors have funky settings for ‘Ultra HD Color’ or something like that that essentially needs to be enabled for 60Hz.
 

caligules

macrumors newbie
Original poster
Jan 21, 2019
3
0
Under Graphics/Displays it says LG 27UK850-W 60 Hz, I already checked that out, that was my first thought too. I'm thinking that if it was just a problem of refresh rate, it wouldn't stutter, just lag. I will buy tomorrow another cable, it seems like the cable from the charger doesn't work for displays, I think it's locked by Apple. I don't know anything about that 'Ultra HD Color'. But at least can you confirm that in normal conditions, my Macbook Pro should be able to run a 4K monitor without these performance issues? At least this way I know if it's worth bothering.
 
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