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by adam mathes
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LG 5K Monitor with a Windows PC

Despite being officially unsupported, the LG UltraFine 5K Display can mostly work with a Windows PC that supports Thunderbolt 3.

You can even use your existing GPU to drive it with the right hardware. The USB-C ports on the monitor are recognized and works properly. The speakers work too. (They’re terrible, but they work.)

Major caveat: Only 4k as max resolution, 5K is trickier right now.

This is fine for my usage – gaming on PC, everything else on Mac. But if you’re looking for true 5K you may need to get the pricier Dell 5K monitor or try one of the few motherboards that claim to support 5K out of the box mentioned below.

How

Hardware:

I used an Asus Z270A-prime which isn’t on that list but Asus explicitly notes is compatible.

I suspect most recent Intel boards with a 5-pin thunderbolt header will work, as it did for John Griffin who used a similar setup as me but with a Gigabyte motherboard.

After connecting the add-on card to the motherboard, you do an external connection from the Displayport on your GPU card to a mini-displayport input on this card with the included cable.

Then connect to the LG 5K monitor with the Thunderbolt-3 cable.

The display powered up and worked at boot instantly for me, including showing the POST screens.

Support for the USB-C hub and speakers on the monitor required me to make a few BIOS changes to enable Thunderbolt-3. I guess TB3 support needs to be enabled explicitly, but somehow the Displayport passthrough on the card doesn’t require it? Which was convenient but very confusing.

What Works

On a PC with Windows 10 –

  • 4K – 3840×2160 @60hz
  • Speakers – (but again, why) and volume
  • Hot swapping the cable between Mac/PC
  • USB-C hub (probably)

What doesn’t work –

  • brightness adjustments (though maybe that’s fixable)
  • reliable USB device recognition on hot-swaps
  • the webcam (haven’t tried to figure out why)

The USB-C hub passthrough was recognized and appeared to work, but wasn’t reliable for me on hot swaps. It was always fine on a fresh boot.

That’s hard to debug or speak definitively on as I’m only using it with legacy USB-A peripherals (keyboard, mouse, speakers) that are connected to a cheap Amazon Basics hub, which is then connected via Apple’s USB-A to USB-C adapter. (I think the USB-A hub is the unreliable part.)

Hot swapping the cable generally worked fine, except for flakiness in recognizing USB devices, and sometimes plugging individual devices in and out of the hub fixed it. It worked enough of the time that I suspect swapping out my old USB-A hub may fix it.

Why

I bought the 2016 Macbook Pro a few months ago, and part of my excitement around it was the LG UltraFine 5K Display that Apple announced at the time.

It’s a native resolution of 5120×2880 at 27”, so it has the same screen real estate as a 27” 2560×1440 but doubling the clarity and pixels per inch. It looks really good!

My challenge with it was I have a gaming PC running Windows so I can play real computer games and use my HTC Vive and I didn’t really want to have two monitors on my desk. I also really like having my monitor act as a USB hub and KVM since I use both a Mac laptop and a desktop PC.

Previously I was using the LG 34UM95 34” ultrawide monitor for this – it supported Thunderbolt 2 input from my mac and Displayport from the PC, and happily swapped the USB devices between them.

So I’m losing the KVM aspect with this setup – I have to actually swap the cable between the desktop and laptop.

But the gains – 5K retina resolution on the screen I use most makes a huge difference – and while I enjoyed the 21×9 aspect ratio for gaming it is much less hassle and equally nice to go back to 16×9 but up the resolution to 4K. (Performance of 3440×1440 and 4K on my GPU, a 980TI, is usually about the same.)

Other Compatibility Notes

The LG UltraFine 5K will also work with older Macbook Pros I tried, but at lower resolutions.

As noted in Apple’s support page, most Macs from the past 3 years will drive it at 4K – 3840×2160 at 60hz – the 2014 Macbook Pro I tested worked as expected.

Not noted on that page but tested and verified by me: my first generation 2012 Macbook Pro with Retina Display will drive the display via the Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter, but only at 2560×1440. I couldn’t get USB devices to be recognized or work, just video.

While it doesn’t make sense to buy this monitor except for a recent generation Macbook Pro that can drive it at 5K, you will (in most cases) be able to use this as a secondary display for older machines if needed, which is nice.

Alternatives on the pc side – the Gigabyte GC-Alpine Ridge looks like it should also work, and has dual Thunderbolt 3 ports, and (seemingly) two Displayport inputs. It claims to enable 4K video, and I suspect it’s possible that it supports dual stream and could drive 5K in some cases but nobody seems to be able to actually buy this card in the US or test it from what I could determine.

Gigabyte also produces some motherboards natively support 5K output over Thunderbolt 3 –

I assume these would be limited to the integrated graphics on the board, so wouldn’t be interesting for my gaming setup, but at least one person has gotten the Z170X Designare to drive 5K on the tonymacx86 boards.

Conclusion

The LG Ultrafine 5K is on sale (30% off) at Apple through the end of March so if what was holding you back was PC compatibility, there’s now at least a few documented examples of it working. Mostly.

It’s still early days of super-high resolution displays, so things are a little trickier to get working. I suspect in a year or two 5K and 8K monitors and supporting motherboards and GPUs will be much more prevalent. If you want to live on the bleeding edge now, you have to be picky about your parts.

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