The LG 34um95 yosemite resolution bug is pretty annoying. I have an lg 34um95 screen – it runs at 3440×1440 – its a great screen, unless you have upgraded to OSX Yosemite.

This issue is now fixed on Yosemite 10.10.2 – if you are using a macbook air, then you can get 2560×1080 with your laptop open, and you can get the full 3440×1440 if you close your laptop and use only the LG screen

Just a quick update to confirm that this does indeed work on 10.10.1, though you have to do the whole process again after you run the update

The LG 34um95 yosemite resolution bug is pretty annoying.

I had a few looks about the forums, and found others with this issue too. eventually someone posted a potential workaround (that involves taking a feramebuffer driver form a mavericks install and modifying it and loading that during boot)

I tried this out, and it didn’t work (at first) so I had to come up with a few extra steps: here is the method I used.

1) download KextBeast

2)download the (pre-patched) mavericks kext file from this thread (thanks :D ), or follow these instructions and patch your own (remember that you need to patch the kext from Mavericks, not the one you have in Yosemite)

3)copy your existing AppleIntelFrameBufferCapri.kext somewhere safe
4)run this in a terminal

sudo nvram boot-args=kext-dev-mode=1

5)move (or copy) your now patched kext to your Desktop
6)run these commands in a terminal:

cd ~/Desktop
sudo chmod -R 775 AppleIntelFramebufferCapri.kext
sudo chown -R root:wheel AppleIntelFramebufferCapri.kext

7)run KextBeast which will install the patched kext from your desktop to where it needs to go
8)reboot
9)delete the patched kext from your desktop (or move it somewhere safe just incase)

Enjoy

Sources:

the forum posts:
https://discussions.apple.com/message/26870149?ac_cid=tw123456
https://discussions.apple.com/thread/6240037


18 Comments

Jay · October 20, 2014 at 2:52 pm

Hi Jonathan, thanks a lot for this blog post. I’m on a mid-2012 MBA and had been happily running a 34UM95 at 3440×1440@50hz prior to upgrading. I tested the Yosemite beta previously and had the issue of no 3440 support, so I restored. I tried again with the full release hoping this issue was gone, but as you know it hasn’t. I had a really painful experience trying to restore my mavericks install the second time, I somehow ended up with a drive-less partition that could only be resolved by booting to a bootable USB drive and killing the whole partition. Before I go through the steps of installing Yosemite again, can I just quickly ask how you’ve found the fix you’ve detailed? Has it been stable?

    jonathan · October 20, 2014 at 6:48 pm

    So far its been very stable, nothing complains, and everything works like it used to :D

    Barry Ghotra · March 8, 2015 at 8:42 pm

    Could you please share how did you or what steps you had taken to make it work on the MBA 2012. I’ve the 34UM95 and can’t make it work at all with either the thunderbolt or HDMI cables (TB to HDMI adapter). the screen shows garbled when first connect and then the display keeps goning-in-out on my MAC. the same monitor works fine with the dell laptop. Any clues or steps to take. I was able to installt he split screen the true color apps on mac but no luck installing the ASM software. I read somewhere that it’s needed to run the MBA using TB cable. I have 10.9.2 with HD4000 GRAPHICS card. Any help would be great. will check for reply, if someone can be helpful.

    Thx.

Stefan Wrobel · November 1, 2014 at 11:00 pm

Thank you! I can now use my Dell P2815Q 4K display in HiDPI mode again!

Frank Brennecke · November 4, 2014 at 11:08 am

Hi,
you should also mention that disabling kext signing could cause problems in case you perform a NVRAM/PRAM Reset. The kext signing flag is stored in this RAM, and resetting it will lead to a grey question mark instead of a working Mac. So one should restore the original Yosemite kext before performing the PRAM Reset. For more information see http://www.cindori.org/trim-enabler-and-yosemite/
Regards
Frank

Gustavo · January 10, 2015 at 8:50 pm

Hi,
I have an ASUS pb287q monitor and I did all the steps twice but no 4k resolution with my 2012 MacMini (entry model) even after going to system preferences, displays and clicking on “scaled” with the alt option key hold down. I’ve done a clean install of Yosemite and it still didn’t work. I’m wondering if I’m doing something wrong (I’m not a newbie and the steps are fairly easy to follow) or if my monitor is not compatible with Yosemite/MacMini. Unfortunately, I can’t try on any other 4k monitor. I’d appreciate any help.

Thanks

    jonathan · January 13, 2015 at 7:06 pm

    Not sure with other screens, but this fix may be screen dependant

    James · January 18, 2015 at 6:04 am

    The HD4000 on board GPU is not capable of typical 4k resolutions. 3440×1440 is the max resolution possible with the HD4000.

JShasta · January 11, 2015 at 3:15 pm

I have a early 2013 MBP w/ Intel HD Graphics 4000 and this fix is not working for me. Am I doing something wrong/is this not possible on my model?

Neon43g · January 13, 2015 at 5:27 pm

Hi there! Thanks for this instructions, but i still have some problems with my 34 inch screen. I run yosemite on MBP13 mid2012 with HD4000 graphics. I tried your instructions with both original 10.9 and patched kext file. After applying kext and restarting my mbp runs great with 3440px resolution. But after second restart or sleepmode i have that strange artifacts in bottom part of screen (looks like frame buffer issue). Do you have any suggestions on this? maybe i did something wrong?

    jonathan · January 13, 2015 at 7:05 pm

    I’ve also noticed this behaviour – only after the system goes to sleep – I’ve resorted to setting my mac to not sleep or turn on the screensaver and using the button on the screen to turn the screen off – not the best solution, but its the best workaround I have just now

Per · January 30, 2015 at 9:39 pm

Hi. I have ugraded to 10.10.2. But I still don’t get better than 1080p on my 13 inch MBAir late 2010 with NVIDIA GeForce 320M 256 MB.
Cable is mini DisplayPort to DP on monitor Aoc q2770 pqu. So all specs are there but not the resolution. Bought the monitor to get 2560 x1440 but it does not work. Annoying! Rgs Per in Stockholm

John Smith · January 31, 2015 at 11:07 pm

I have a macbook air mid-2012 (10.10.2), with the lg 34um95 connected by mini-displayport (mba) -> displayport (Lg34um95), I have this problem where its limited to 2560×1080 even with closed clam.

I tried your fix without success, also with the ‘option’ + ‘click’ on ‘scaled’ but the 3440px option never shows up.

Any ideas?

Thx

    jonathan · February 1, 2015 at 11:13 am

    Hi John
    I only tried this with thunderbolt cables, but I can confirm that it is fixed when using thunderbolt (but the cables are expensive) :|

cranckhead · March 31, 2015 at 12:18 pm

Hi, I have a Mini Mac 2012 Server model (HD4000 Graphics) and run Yosemite 10.10.2 with 1 LG 34UM95 display (TB cable). I know the Mac Mini is capable of running 2 Apple TB screens (daisy chaining), would it be possible to hook up 2 LG 34 screens (daisy chaining)? Thanx!

    jonathan · March 31, 2015 at 6:42 pm

    not sure, I only have one screen so cant test it with the daisychaining :|

Daren Jacobs · January 27, 2016 at 6:38 pm

Where is this preached version of the Mavericks file that you speak of. Can you put it on your site?