LG 34WK95U (5k 2k) display with only 30 Hz refresh rate with egpu

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18 points

LG 34WK95U (5k 2k) display with only 30 Hz refresh rate with egpu

Hi,

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.

Posted on Jul 30, 2020 1:08 PM

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Answer 1

Leanne_68

Community Specialist

Aug 3, 2020 11:55 AM in response to keven4ever

Thanks for the additional information.

It's not directly confirmed, but do you have FileVault enabled? Using the Mac mini (2018), it's possible that the behavior you're seeing could be caused by FileVault. Learn more about FileVault here: Use FileVault to encrypt the startup disk on your Mac.

"If you have a Mac mini (2018) with FileVault turned on, make sure to connect your primary display directly to Mac mini during startup. After you log in and see the macOS Desktop, you can unplug the display from Mac mini and connect it to your eGPU."

That statement is located under "Learn More" in the subtext on the document provided about using an eGPU. Your routine seems to fall in line with what this suggest and this may be something expected.

There are six additional suggestions mentioned in that same list with various Mac models in mind including some MacBook Pro models.

Cheers!

Best wishes!

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Answer 2

keven4ever Author

Level 1

18 points

Aug 3, 2020 7:27 AM in response to A_J_Rabbit

Hi, thank you for your reply, I have tried suggested solutions but still not fully working as expected. Also I have upgraded to 10.15.6 already.

You are right about the setup, I didn't use Thunderbolt 3 connection because I have another 2018 MacBook Pro which is connected the same monitor via Thunderbolt 3.

For Mac mini, I use provided Displayport cable which has a 5K label on it, so I believe it supports Displayport 1.4. However, every time after reboot, I only get 30 Hz refresh rate and the option to choice other refresh rate is disabled in Mac settings. So I have to go to monitor settings, switch from DisplayPort 1.4 to displayPort 1.2, then switch back to Displayport 1.4, then I can select different refresh rate like 60Hz. Also, before this DisplayPort settings change back and forth, some resolution is also not available.

Secondly, when I connect to monitor with egpu, I can select HiDPI resolutions like 3440x1417 60Hz, but as long as I involve egpu (Mac min to egpu and egpu to display), I can't find these HiDPI resolutions any more (only 3440x1418 60Hz). I can clearly see with HIDPI resolution is mush sharper.

thirdly, in egpu setup, if I simply restart Mac mini, it just shows black screen and never able to see login window. however, if I first shutdown machine, then wait for 1 min, then start the Mac mini by pressing power button, in most case it can start successfully. I never have this issue when exlcude egpu. I saw this issue in different community includes this forum, will apply fix this issue soon?

Last, with my MacBook Pro 2018 and without egpu, using thunderbolt 3 connection, sometime when MacBook Pro wake up from sleep, HIDPI resolution is not available neither, I have to change switch input of monitor to another source, then switch back, then it shows those HIDPI resolutions. Any idea why?

BR/Keven

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Answer 3

raina_b22

Community Specialist

Aug 6, 2020 1:01 PM in response to keven4ever

Hello there, and thanks for the update.

In this case, you may want to test with an alternate monitor. Also, if you have the opportunity to test with the alternate configuration using Thunderbolt 3 only, this would be great for help with getting to the bottom of these concerns with the refresh rates and resolution.

You mentioned that you plug in the monitor without the eGPU, but are you getting refresh rate and resolution issues if you use the eGPU on the MacBook?

Stay awesome!

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Answer 4

keven4ever Author

Level 1

18 points

Aug 7, 2020 8:27 AM in response to raina_b22

Hi,

Yes, I don't have most of these problem with another LG HDR 4k monitor except that it shows black screen when reboot with egpu setup, also sometime the the entire screen just freeze when wake up from sleep.

Also I tested with Thunderbolt 3 without egpu involved, much better. Although sometime it doesn't provide some specific resolutions like 3360x1417 60Hz with HiDPI, but if I switch to another input then switch back, it gives me back this resolution which I prefer as other resolutions are all a little bit blur. Another problem is that sometime there is no sound from monitor, it works at the beginning, then after use a while and wake up from sleep, it lost the sound. Also I tested with a DisplayPort to USB-C port, connecting USB-C to Mac min and DisplayPort to monitor (without EGPU again). however, this setup only provides DisplayPort 1.2, so I can't get this 3360x1417 60Hz resolution again.

In general, I feel this monitor with 5k2k resolution doesn't work well with Mac mini, actually works slightly better with MacBook Pro.

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Answer 5

keven4ever Author

Level 1

18 points

Aug 3, 2020 12:51 PM in response to Leanne_68

Hi,

I can confirm that FileVault is NOT enabled on my Mac mini.

BR/Keven

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Answer 6

A_J_Rabbit

Community Specialist

Aug 2, 2020 6:48 PM in response to keven4ever

Greetings keven4ever,

Welcome to Apple Support Communities!

It sounds like, you're using an Apple Mac Mini and Razer Core X RX 580 eGPU. Your configuration is understood as "a Thunderbolt 3 cable connected between Mac mini and the eGPU, then there's a connection with the Display port cable between the eGPU and LG 34WK95U"

First, verify that you've set up the display to be the primary display by following the steps under the, "Set an external eGPU-connected display as the primary display," section of this article: Use an external graphics processor with your Mac. From this same article you'll find additional specifics for your Razer Core X eGPU in the, "AMD Radeon RX 5700, 5700 XT, and 5700 XT 50th Anniversary," section.

Next, making sure the software on the Mac is up-to-date will be important. For your eGPU you'll want to be sure that you have installed macOS Catalina 10.15.1 or later. For help with updating your macOS, check out this link: Keep your Mac up to date.

You should not have to swap back and forth to get the results you're looking for, but if you have to go to the display itself to make these changes, this may have something to do with the port version swapping on that single component. You may need to reach out to the manufacture to find out if this can be corrected. In summary, it sounds like the preference is not specifically saved in the LG 34WK95U.

As for the connection, you may want to check to make sure you have the proper cables. Often, cables can seem to be compatible or qualified for use, but they simply aren't.

When you power on your Mac, like most computers, there's a POST (Power On Self Test). It's likely that the Mac mini is either not getting the correct signal from the display and swapping to a default, or one of the two external components is providing the unwanted settings as the status. You can reset the NVRAM, this will clear old saved configurations on the Mac mini. Learn more here: Reset NVRAM or PRAM on your Mac.

The physical configuration sounds correct, but you can look for solutions that eliminate the need for using the display port between the eGPU and LG. This display specifically has a Thunderbolt 3 connection as well. It's possible that this issue may be related to firmware and software in each component used in this setup. However, here are a few additional documents that may help:

Best wishes!

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LG 34WK95U (5k 2k) display with only 30 Hz refresh rate with egpu

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