External 4k Monitor on Lenovo Yoga 2 Pro

Solution 1:

I'm using it with a AMH A399U 3840x2160 monitor with a microHDMI–HDMI cable. Getting 30Hz.

Hardware

The HDMI connection seems somewhat sensitive — at some points some of my cables and/or one of the 2 HDMI ports on monitor didn't work at 4K. I'm unable to say if the laptop, the cables or the monitor were to blame. But overall I've settled on a connection that works.

Apparently the Yoga's HDMI port is slightly too deep for some cables, can be fixed by shaving off some plastic. I haven't tried that but I can confirm moving the cable (any of several I tried) easily disconnects it.

On frequency: My monitor claims 60Hz via HDMI 2.0 and DisplayPort; the Yoga 2 Pro is only capable of 30Hz over its HDMI 1.4 (or 1.3?). (IIUC HDMI 2.0 is not coming to laptops anytime soon, except maybe via nVidia cards.)

On MST / single-stream: I think my monitor uses MST to achieve 4K (pretends to be 2 screens). This is invisible to me — all software treats it as one video output. Can't say if it will work with newer single-stream monitors (don't know if Yoga can send single stream nor if all such monitors also accept MST). I think that's a hardware—hardware question, so a report from a Windows user for your specific monitor should be enough.

The only non-HDMI way to get 4K out of the Yoga is via USB3 -> DisplayPort or USB3 -> HDMI adapters; I haven't tried any and I'm not sure there are any exist with linux drivers (Pluggable are fantastical about linux and but none of their 4K adapters does). Also, I think they all use lossy compression to fit USB3 bandwidth.

Performance

We're using it for reading and coding, and some movie watching. The Haswell GPU is definitely not enough for 3D gaming at 4K.

4K streaming from Youtube doesn't work well. Left to "auto" it settles on 1080p / 1440p. Not sure if it's network speed (10–20Mbps here) or decoding speed but I'm resorting to youtube-dl and then playing locally.

4K decoding in Gnome Videos app and MPlayer seems to be smooth; VLC tends to struggle. However there's constant screen tearing. I suspect that's resolvable, haven't looked into it yet.

Software configuration

Turning off the internal display and enabling the HDMI just worked.
So did extending the desktop — half here half there (I did it vertically; don't remember if there was a horizontal width limitation or I just wanted one on top of the other). In any case, due to the Yoga screen's very high pixel density, it was an awkward setup. (Per-screen UI scaling is practically non-existant in linux yet.)
Touching things on the laptop's screen is sometimes nice, so I settled on a config showing same desktop on both screens. The resolutions are not that different, so I'm set it to draw at 4K and scale down for the internal screen, using this command:
```
xrandr --output HDMI1 -s 3840x2160 --transform none --pos 0x0 --output eDP1 -s 3200x1800 --scale-from 3840x2160 --pos 0x0
```
[https://github.com/cben/myenv/blob/master/bin/4k]

Solution 2:

I connected dell UHD 4K monitor to Lenovo Yoga 2 Pro laptop. Then pressed window key+P key. Selected external monitor only. I got 4K signal at 29HZ. For regular work it is fine.

Solution 3:

Well according to Intel ark, it isn't specified to be able to output a resolution over 3280x2000, so I'm pretty sure 4K is going to be a bad idea, if it works at all. This system is prone to running warm, and 4K wouldn't be very comfy for the iGpu even doing menial tasks