LG 34WK95U (UltraWide 5k monitor) and MacBook Pro 2018

Even if the Thunderbolt to DP works for Macbook, my DP is taken by my Windows box and I would hate to manually switch the cables on the back of the monitor every time I need switch between the machines. 😠

One more interesting update: I've booted up into my Bootcamp with Windows 10 on the same Macbook and the display works properly over the Thunderbold 3. This probably proves that the problem is not on the hardware side and more of a macOS issue.

Hi Alex, so if I understood correctly, from the Touch Bar or from the external magic keyboard is not possible to control directly brightness and volume as happen with the macbook display, Apple Thunderbolt Display or UltraFine.

Is it correct?

Just unboxed my 34WK95U tonight, confident I wouldn't have the MacBook Pro problems since I have a 2016 MacBook Pro 15. But I did! Thunderbolt connection will only give me 3440x1440. Tried SwitchResX, no improvement. Did minor security update (only update available to me), no improvement.

Called LG, they claim my laptop "must not support the 5K resolution", which is obviously incorrect, I should be able to drive 2 of them. Suggested I try different cables/connections. But after digging deep into my cable stash, was not able to find an alternate that the LG would recognize at all. Best I could do was a USB-C to USB-C instead of the Thunderbolt cable, as the LG chart on their notice page suggested would work, but it didn't. Monitor told me I would "need two USB-C cables" (??), which I don't entirely understand, bc where would it even go?

So I'm sitting here trying to figure out if I'm mad enough to box this thing back up, or gamble on another cable, or wait for Apple to solve it. My inclination is to wait on Apple to solve it, but I'm concerned about why is my 2016 MBP is causing me 2018 MBP problems with this monitor? From everything I've read, I shouldn't be having this problem.

Note: I already have the LG Ultrafine 5K display at my other office, use with this same MBP, and it gives me no trouble. Connects, charges, and gets full 5K resolution via Thunderbolt.

UPDATE: SUCCESS! After six hours of frustration with cables and settings, I just upgraded aforementioned 2016 MBP to Mojave from latest Sierra and it worked! Thunderbolt working as it should. I still had to use SwitchResX to actually select the 5120x2160 resolution, but just that one extra step and it works perfectly.

Holy crap that's a lot of pixels!!!

Also, for what it's worth for those still struggling, if this hadn't worked, my next step was going to be a solution I just read was working for many others: Connect a separate power cable to the MBP (the factory charging brick/cable) in addition to the TB cable going to the monitor, and make sure the TB is in the front right port for some reason. Worth a shot if you haven't tried it.

I suspect there's some validity to it, since the message I got on the dark monitor when attempting to swap the TB cable for a USB-C was that I "need 2 USB-C cables". I think it was trying to say you need power separately. Even before trying the USB-C, I noted the resolution is was giving me with the TB was as if it wasn't recognizing it as a TB cable.

2016 MacbookPro 15

Until the Mojave update just a few minutes ago, it was the latest Sierra with all security updates. At the beginning of this saga tonite, I hadn't done that latest security update, did that somewhere in my troubleshooting, made no difference.

Processor: 2.9 GHz Intel Core i7

Memory: 16 GB 2133 MHz LPDDR3

Graphics: Radeon Pro 460 4096 MB, Intel HD Graphics 530 1536 MB (both)

Drivers: I did no manual driver updates

Cables: ultimately just the LG supplied TB cable worked for both power and video, after Mojave update

Extras: I did need to use SwitchResX to actually select the 5120x2160, but it was just a click, didn't have to do any crazy recovery boot/terminal work.

****! I forgot about option-clicking the word scaled. I was doing that earlier, frankly just forgot after Mojave upgrade. Just checked and that would have worked, too. So SwitchResX wasn't necessary after all.

The clarity and resolution looks identical to my eyes. Unfortunately I don't have them both in the same location so I can't see side by side. This ultrawide covers a ton of eyeball real estate. If they made a 5K in a curved model, I would consider that, but I suppose it depends on how close you sit. I haven't really worked with it long enough to learn to position my windows to take advantage of my newfound screen space, but I will.

It's essentially the ultrafine, just much, much wider. I like it! Just depends on if you want that much space to work with or not.

I have the same issue with MacBook Pro (15-inch, 2016)

Radeon Pro 455 2048 MB

I got the 5k resolution working before, but since the Mojave update it doesn't work at all anymore.

Have you been able to find a solution?

Not really felt like smaller vertical space, bc the extra horizontal grabs all of your attention. I feel like the 2160 is plenty. At full resolution, if the menus and etc. were any smaller, you literally wouldn't be able to read them. I mean really, either 2160 or 2880 at this size is starting to approach imperceptible-to-human-eye type resolutions. So it definitely feels like plenty.

I can reproduce the above steps on my MacBook Pro 2018. Minor change...

1. Shut computer down.
2. Plug Power Cable into the right rear Thunderbolt-3 connector.

3. Start Computer

4. The second the keyboard lights up, plug in the monitor to the right front Thunderbolt-3 Connector.

( If it doesn't work try again. It's a bit of a timing thing.)

I could not reproduce this without the power cable.

I could not reproduce this moving both cables to the left side connectors.

I don't think that adapter supports 5K over a single DisplayPort connector. Realize that frame buffer size does not always equal output resolution. It's possible that the output resolution in your case is 4K. The 5K frame buffer is scaled down to fit the output resolution. Another possibility is that the output resolution is 5K 30Hz instead of 5K 60Hz.

Some displays will show the output resolution and refresh rate. This is usually the case with my Dell displays except for HDMI resolutions where for 4K it says 2160p without the refresh rate so I can't tell if it's doing 30Hz or 60Hz.

The best way to see the output resolution is to double-click the current resolution in SwitchResX and note the active vertical and horizontal pixels, and the vertical scan rate. Also, note the pixel clock - it should be approximately 966 MHz for 5K (16:9), approximately 703 MHz for 5K2K (21:9), 533 MHz for 4K (DisplayPort), and 594 MHz for 4K (HDMI 2.0).

That Ableconn TBT3-DPX2 is just another of the more than 20 Thunderbolt 3 to Dual DisplayPort 1.2 adapters the I mentioned. Like I said before, they only support 5K 60Hz when you connect two DisplayPort 1.2 cables to the display and the display uses one DisplayPort connection for the left side and the other DisplayPort connection for the right side. These are displays that support.apple.com calls "dual-link SST" or "dual-cable displays".

You need a Thunderbolt 3 to Dual DisplayPort 1.4 adapter which are very new and very rare (I only know of the one I linked).

Or just use a USB-C to DisplayPort cable that is certified for DisplayPort 1.4 or 5K 60Hz such as the Moshi cable sold by Apple that I linked previously.

There is some evidence that the "LG 34WK95U" uses a "dual-link SST" mode similar to the LG UltraFine 5K when connected via Thunderbolt 3 which allows 5K2K 60Hz with Thunderbolt 3 Macs that don't support DisplayPort 1.4 (they use Alpine Ridge Thunderbolt 3 controllers or they use Intel integrated graphics).

DisplayPort 1.4 is preferable to DisplayPort 1.2 dual-link SST because it's more efficient and less complicated. I have an Nvidia card connected to a Dell UP2715K which has the problem in macOS where the cursor is incorrectly set and differs between the left half and right half of the screen. I don't recall that being a problem with AMD or Intel graphics - but it is a problem that could not exist if I were using a DisplayPort 1.4 display.

Hiya

Last post on this thread was the end of November. I just bought a 2018 MacBook Pro 15" - does anyone know if this problem is resolved in MacOS releases - before I go spend a fortune on one of these monitors.

Thanks