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LG 34WK95U Displayport problem  

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theone4ever
(@theone4ever)
New Member
Joined: 2 weeks ago
 

Hi egpu Mac fellows,

 

I have a 2018 Mac mini and Razer Core X RX 580 GPU. My setup is connecting Thunderbolt 3 cable between Mac mini and egpu, then display port 1.4 cable from gpu to monitor and I set the display port version at 1.4 in 34WK95U. However, there are two issues:

1. I prefer resolution 3840x1640 which works but with only refresh rate at 30Hz right after restart. I have to go to monitor's setting to switch the DisplayPort 1.4->1.2->1.4 then I can select 60Hz. it seems when reboot, there is communication issue, Mac mini believes only 30 hz is available for this resolution, so after switch back and forth after login windows, it works fine. This is a quite annoying issue that every time I restart machine, I have to switch DisplayPort version in monitor back and forth. 

2. if I just do restart, then there is black screen. but if I first shutdown Mac mini and wait for few seconds, then start machine, It can boot without black screen but it takes longer time to boot. I know this is known issue, just wonder if there is some better tip then either plugin another HDMI cable or wait for few seconds to start?

 

Thank you in advance.

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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joevt
(@joevt)
Noble Member
Joined: 3 years ago
 

Maybe Big Sur beta install changes eGPU boot behaviour?

3840x1640 is less than 4K so it doesn't really require DisplayPort 1.4. But I think you mean that you are using a 3840x1640 HiDPI scaled mode which uses a frame buffer of 7680x3280 and is scaled by the GPU to output at 5120x2160 which is greater than 4K and does require DisplayPort 1.4 (actually, 5120x2160 only requires DisplayPort 1.2 when using 8 bpc - DisplayPort 1.4 is needed for 10 bpc or HDR).

I think 1640 is wrong - should be 1620 if you want the same aspect ration as 5120x2160.
3840x2160/5120=1620.

Maybe you can use SwitchResX to change the startup resolution? It can at least verify the current resolution timing information (just double click the current resolution in the Current Resolutions tab for the display in SwitchResX).

 

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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