I recently got the lovely FO48U monitor as a gift and want it to use it with my work laptop which is the M1 Max, Macbook Pro 16"
I then went online and bought a Deltaco USB-C to DisplayPort 1.4 1.8m 8K cable.
It’s rated to run 4K@120hz and got this cable recommended.
The display is detected within MacOS Monterey and is saying 3840 x 2160 with Variable refresh rate (24 - 120Hz).
Whenever i switch the source to DisplayPort the screen goes black, disappear briefly in MacOS and then it switch back to HDMI 1 where my desktop is connected to.
I have tried to change the resolution down and also lowered the hz down to 60 or even 24, nothing gives me display.
If I set the screen to PBP in a half/half setup i can get a picture up, i’m unsure what resolution it runs but i believe it’s 4K since that wasn’t changed.
So I am totally lost in what to do, to get proper 4K resolution.
I can accept 60hz simply because i am mostly doing text based stuff I just want 4K with no insane scaling.
I can tell you that 4k@120Hz is only possible over DisplayPort 1.4 if you tweak the protocol by creating a custom modeline. I know how to do this under Linux only. Normally DisplayPort 1.4 does not have the bandwidth to do 4K@120Hz without Display Stream Compression!
Apart from that 4K@60Hz should work but I had trouble with MacBooks as well on my FV43U. You might try a direct USB-C to USB-C connection from the MacBook to the screen!
I am aware of 4k@120Hz is only DP 1.4, that’s why I also looked up the specifications for the monitor to see what the port was in the monitor.
the DP port is 1.4 and the HDMI is 2.1.
And I specifically went out and got a DP1.4 cable, my cable also say in the bag it’s DSC 1.2.
No, as I tried to say: DisplayPort1.4 and 4K@120Hz only works in combination with DisplayStreamCompression (DSC). DisplayPort 1.4 has not enough bandwidth for native 4K@120Hz. I do not know if MacOS does even support DSC.
I have a question then, to follow up on DSC.
the user manual say DP1.4 “shares DSC
with HDMI port”.
What does that mean in practice ?
Currently I have my computer running on HDMI 1.
I can’t see in the user manual that the USB-C port in the monitor is for display, since the timing table doesn’t mention USB-C.
I have found a Mac related forum thread talking about DSC support in MacOS Monterey is a problem.
It is only available over dp 1.4 or hdmi 2.1. The macbook doesn’t have a 2.1 port. If you are using hdmi and dp you need an active dp capable or adapter. But as the macbook does not support 2.1 it wont output 4k 120hz.
Yeah I though as much, in regards to DSC. In general 4K@60Hz should work though, at least over DP1.4 the bandwidth would be more than enough. I do not know which (EDID) profiles the screen does advertise to clients though. I tested my screen with an older MacBook and was also unable to set the correct resolution. Some graphic cards also have trouble with my screen under Linux, in the way that they offer only weird resolutions. You might have some success to look into forcing resolution/refresh rate combinations on a display out port on MacOS. MacOS is not a OS I use often so I don’t have this specific knowledge required here.
Let me get back to you both with some screenshots from my laptop.
On my way to bed (EU Time here).
In the mean time, I don’t think the cable is Thunderbolt actually, it’s just USB-C.
I have tried to set the laptop to force 4K@60Hz and even 4K@24Hz and it doesn’t show a picture.
I have also turned the resolution down to 2560x1440@60Hz and that doesn’t work either.
