Running the LG UltraFine 27" 5K Display on Windows 10

Ambrose Little
4 min readNov 11, 2017


Windows 10 Settings for LG UltraFine 27" 5K Display

It’s not as simple as you’d hope, but it’s possible. :)

This is probably the currently best quality monitor on the market, particularly if you have a recent MacBook Pro. That’s why I got it originally. Here’s my review of the LG UltraFine 27" 5K display, if you’re interested in learning more about the display itself.

The thing is, I started working at a shop where I more or less have to run Windows (because of Visual Studio et al), so I started looking around for possible PC configurations and, in particular, ones that would let me use this great display I already have. I stumbled upon this post, which was encouraging. I have Adam Mathes to thank for pointing me in the direction that would work. I’m writing both to confirm the solution as well as provide a few tweaks/more details.

My setup (most relevant to running the UltraFine):

(If you want my full build details, you can get those here.)

The ThunderboltEx 3 card comes with two important cables:

  • Patch cable to the motherboard Thunderbolt 3 header.
  • Patch cable from the DisplayPort out (regular size) of your video card to the in Mini DisplayPort on the extension card.

I don’t know if it matters, but I followed the manual advice and plugged the card into the bottom/last (PCIe 4) slot on this motherboard, patched from the card to the TB3 header, and patched from my video card out to the Mini DisplayPort in on the expansion card.

I powered up, and it worked! Well, mostly. It works as a plain display, but you paid for the included (decent) speakers and camera, right? Well, this won’t work until you turn on Thunderbolt in BIOS. Here are the settings I used:

  • Go to Advanced and find Thunderbolt.
  • Select the PCIe slot you plugged it into. For me this was slot 4.
  • Enable USB.
  • Enable USB Boot. (Not strictly necessary, but why not?)
  • Change CPIe Cache-Line Size to 128 (from 32). I read somewhere that the Apple monitors like this. Not 100% sure it’s necessary, but I’m just sharing.
  • I left everything else as default, similar to what is noted in this forum post.

Once you do that, Windows 10 should detect the new USB controller, and then detect your speakers and camera. At least it did for me.

At this point, you’re good to go! Well, except you won’t be able to change the brightness. To do that, grab this open source utility. It’s not fancy, but after I enabled Thunderbolt 3 in BIOS, it worked. (Before that, I was getting “Failed to open the device (open_device failed)” when trying to run it.) But if you followed the steps above, it will work, and you have a fully functional beautiful monitor that you can use both with your Macs and Windows PCs.

YMMV. :) I am not an expert in PC config and so probably can’t offer much other advice for your setup. I am just decent at Googling and very determined. LOL.

P.S. You’ll note in the settings screenshot above that it is not running at 5K on Windows but rather 4K. But it’s still absolutely gorgeous. The real benefit is that macOS does a lot better on 5K at 27" than it does with 4K at 27", and most 4K displays are 27". So if you want a 27" display that will look optimal on both Windows and Mac, this setup is one of the better options right now.

UPDATE 13 March 2018: Sadly, a recent update (either Windows or latest LG monitor firmware) has rendered the brightness control non-functional on Windows. I’ve also noticed a few cases of the camera just stopping working, and I have to unplug/replug the monitor power. At which point, the brightness may reset. So, I’m gonna have to give up on running this on Windows. YMMV.



Ambrose Little

Experienced software and UX guy. Principal Software Engineer at GLG. 8x Microsoft MVP. Book Author. Husband. Father of 7. Armchair Philosopher.