TB3 monitor doesn't work when "cold-plugged", flickers unless 2nd monitor present

[ckrueger99]

Describe the bug

1. In contrast to "hot plugging not working", TB3 monitor doesn't work in any "cold plug" situation, i.e., from startup or when an HDMI monitor is connected/disconnected. The solution is to unplug TB3 monitor cable, then replug it.
2. When there is no second monitor, the TB3 monitor flashes frequently when there is redraw required (e.g., moving a finder window). Simply moving the mouse cursor doesn't cause this to happen. The solution is to use a "headless" HDMI dongle.
3. The monitor in question, an LG UltraFine, works fine when connected to my MacBook Pro 13,1.

Expected behavior Hot and cold plug functioning of TB3 monitor, whether or not there is a 2nd monitor attached.

Configuration

• HaC Mini version: 2.9
• OSX version: 10.15.5 Catalina
• NUC model: NUC8i7HVK
• Boot SSD model and protocol: Samsung SSD 970 EVO 1TB
• First DIMM model: Crucial DDR4-2400 8GB CT8G4SFS824A
• Second DIMM model (if installed): same
• Display port(s) used [e.g: USB-C, mini DP]: TB3 + HDMI(headless)
• Display resolution(s) [e.g: 4K, 5K]: 5K
• Any TB3 devices: LG UltraFine Display
• Any USB devices: Logitech wired keyboard, Logitech dongled mouse, USB drive

Modifications No modifications except using the Native Thunderbolt option under the custom install. Ran the Thunderbolt Patcher following installation (at least, I think I did this correctly ... The TB3 partially works, so I haven't bricked it. :-) )

config copy.txt config copy.plist.zip

[osy]

For the flickering, did you use the reduce flickering workaround from #7 ?

[osy]

Also try https://github.com/osy86/HaC-Mini/suites/804462105/artifacts/8710642

[osy]

Also curious if you experience this without the headless dongle? I use a LG 5K ultrafine + LG 4K (miniDP to DP) and it works fine.

[ckrueger99]

I only experience it without the headless dongle. With the dongle, the flickering disappears. It's still necessary to unplug/re-plug the TB3 cord at startup as described, however. Also, when it goes to sleep, which I have therefore disabled.

[osy]

I mean without the headless dongle does cold plug work?

[ckrueger99]

No.

[ckrueger99]

The link above leads to a download of an installer which downloads the HaCMini.pkg. What am I supposed to do with this?

[osy]

You install it? It’s the beta for the next release which has updated AMD graphics drivers.

[ckrueger99]

But still better to use the Intel Hardware Video Codec instead of the AMD one? I never understood that.

[osy]

The "codec" is only for HW accelerated video encoding/decoding. It doesn't have anything to do with the GPU and graphics acceleration.

[ckrueger99]

The flickering was solved by installing the "Reduce Screen Flickering" workaround, which I hadn't noticed previously. So I don't need the headless dongle anymore, which is nice. The cold plug problem only affects the TB3 monitor itself, not USB-C device plugged into it. A USB drive, which I have plugged in via a hub which is plugged into the back of the monitor, is still functioning fine, even when the monitor is black. The monitor also appears in the System Report under Thunderbolt and Graphics/Displays when it's black. Finally, the LG monitor often doesn't appear when I hot plug it into my MacBook Pro (solved by sleep/awake sequence), so maybe this is a performance problem with this particular device?

[osy]

If you get a change to try the Big Sur beta, let me know if it works. My 5K UltraFine had no issues. Apple seemed to have fixed a lot of driver issues.