Can I connect 2 LG 5K2K monitors to MBP (2018) on Mojave?

Can I connect 2 LG 5K2K monitors (LG 34WK95U-W) to MBP (2018) on Mojave?

I attempted, but I can only get one to work at a time. If fact, even with one it takes a few seconds for the monitor screen to come on. My specs are as follows:

MacBook Pro (15-inch, 2018, Touchbar, 2.9 Ghz Intel Core i9, 32 GB RAM, Radeon Pro 560X 4096 MB also Intel UHD Graphics 630 1536 MB, 2 TB Storage with 1.65 TB available).

OS: MaOS Mojave version 10.14. Software Updates tells me that is the latest version.

Monitors: Two (2) LG 34WK95U-W. These are the latest 5K2K monitors from LG with Thunderbolt 3 connectivity.

I am connecting both monitors directly to the MBP with the T3 cables provided by LG. Each monitor is connected to a different Thunderbolt Bus (One on the left of the laptop and the other on the right). Nothing else is connected. The power is at 100% being fed by the monitors.

Individually the monitors work on any bus I use. The problem is when I connect both at the same time, only one works (even then it is a hit or miss).

I tried different certified T3 cables. Same problem.

The MBP system information under the Hardware: Thunderbolt: Thunderbolt Device Tree, each bus shows that an UltraWide 5K by LG Electronics is connected. However, only one display is actually working. The Thunderbolt device tree is also showing that each monitor is a different bus.

The are two things I notice that is a little suspect.

First, the cable firmware version for the monitor that is currently working is 0.9.0. They one that is n to working does not show any cable firmware version. Might it be a cable issue? Going to get an exact duplicate cable and test that possibility.

The next thing is that the Link Controller Firmware Version for the Thunderbolt bus is 0.97.0 when there is nothing connected to the port. However, when the monitors are connected, the version number for the connected port is 0.85.0. I contacted LG on how I can update the monitor's firmware and is there a later version than the current one. Waiting for a reply from LG.

Another possibility is that this may be a Mojave comparability issue. I am going to contact Apple to see if they have heard anything.

In the meantime, any ideas on what the issue or resolution might be?

Mac OS 10.14

Posted on Oct 23, 2018 11:30 AM

Top-ranking reply

Ranxerox968 Author

Level 1

8 points

Posted on Oct 24, 2018 8:14 PM

Spent some quality time at Apple with both monitors. The issue is that the Ultra-wide 5K resolution (5120 x 2160) of the LG 34W K95U-W monitor is not supported by Apple/Mojave. Therefore, drivers are needed from either Apple or LG.

An interesting find was that although we used the LG supplied cables, the monitors did not work. However, when using the Belkin 4K (USB-C cable 1m (3 ft)) 3.1 Gen 2 (10 Gbps) Video transfer capable -- both monitors came up fine. However, at 4K not 5K. Will continue to use until support is provided by Apple or LG.

Another factoid, to get 5K on each monitor, it is recommended that the ports used on the MacBook Pro are the back two (furthest most from the front of the laptop).

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Can I connect 2 LG 5K2K monitors to MBP (2018) on Mojave?

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