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Can someone with an iMac 5K check if Linux works at 5K?
- Thread starter tornado99
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It might not work, but I actually wrote these code snippets wrong. The correct versions are:
Code:
video=eDP-1:5120x2880MR@60or
Code:
video=eDP-1:5120x2880MR@60-24If the position of the MR is wrong it is ignored completely.
The above snippets should be inserted into your kernel command line which normally has "quiet splash .... " in it.
sudo nano etc/default/grub
[edit and save file]
then
sudo update grub
then
reboot
hi all, i can confirm the same thing on my 2019 5k imac. i boot arch linux with wayland through opencore chained to grub and wlr-randr shows only half on the 5k, while trying to force 5k through mango's config just applies the half-5k skewing the image.
what's interesting is that grub seems to recognise and properly render the 5k resolution, because i used to boot through it without opencore and the image was bigger.
Code:
GRUB_CMDLINE_LINUX="amdgpu.dc=0 amdgpu.dpm=1 video=eDP-1:5120x2880@60"
GRUB_GFXMODE=5120x2880,3840x2160,autofully working 5k on X11
amdgpu.dc=1 amdgpu.mst=1 video=eDP-1:5120x2880@60
xrandr --newmode "5120x2880" 1276.50 5120 5560 6128 7136 2880 2883 2888 2982 -hsync +vsync
xrandr --addmode eDP "5120x2880"
xrandr --output eDP --mode 5120x2880 --pos 0x0 --primary
amdgpu.dc=1 amdgpu.mst=1 video=eDP-1:5120x2880@60
xrandr --newmode "5120x2880" 1276.50 5120 5560 6128 7136 2880 2883 2888 2982 -hsync +vsync
xrandr --addmode eDP "5120x2880"
xrandr --output eDP --mode 5120x2880 --pos 0x0 --primary
queryingquagga
macrumors newbie
Did this work for you? I’m questioning buying an 2017 5K 21,5 inch 16GB ram AMD 555 iMac, but I would like to be able to keep 5K resolution in Linux.
Does this also work under wayland? Given the deprecation of x11 in a few major distros, having this working under wayland seems to be the best for mid to longterm.
Huh I somehow missed this post, huge if true!
Can you specify which iMac model you're using, and which Linux distro? (and if possible, kernel version)
i actually got given a 5k for free recently! but not tried
solution is described here
it is strange that the author doesn't mention wayland working, but I am now more confident that it will eventually work on wayland too as the aim is for wayland to be feature parity with x11.
for the smaller 21.5 imac you need to add video=eDP-1:4096x2304MR@60 after quiet splash in the kernel command line. works fully on wayland.
solution is described here
it is strange that the author doesn't mention wayland working, but I am now more confident that it will eventually work on wayland too as the aim is for wayland to be feature parity with x11.
for the smaller 21.5 imac you need to add video=eDP-1:4096x2304MR@60 after quiet splash in the kernel command line. works fully on wayland.
@antibolo the guy in the linked threat explicity got it running on a imac 18,3, oclp > grub, on ubuntu 25.10 with x11. So far, ive not seen any confirmed success on wayland. I'll try it when i have some free time.
From what i understand, it should also work with systemd-boot, if you write the arguments into /etc/kernel/cmdline, but correct me if im wrong on that.
As i intend to run pop_os on the imac, ill try these steps on this system and post the results here.
apparently full 5K on Wayland with KDE might be possible with this:
invent.kde.org
It is only available in Plasma 6.6.0 which was released last week. Anyone want to test?
add support for custom modes on Wayland (!266) · Merge requests · Plasma / libkscreen · GitLab
Depends on kwin!8534 With this, you can add...
invent.kde.org
It is only available in Plasma 6.6.0 which was released last week. Anyone want to test?
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redsun@bazzite:~$ xrandr | grep "*"
5120x2880_60.00 59.99*
with parameter given by tornado99, got it working in imac 2017 5k 27 inch on bazzite 43 kde x11
5120x2880_60.00 59.99*
with parameter given by tornado99, got it working in imac 2017 5k 27 inch on bazzite 43 kde x11
Reposting this from gitlab (the original author seems to have used AI to format it, but I guess the contents are true!). Personally I prefer Ubuntu GNOME, so hopefully they will have a similar feature soon.
The following parameters must be passed via the bootloader to override bandwidth safety checks and ensure stable display initialization:
kscreen-doctor successfully injects the native 5K mode into the Wayland compositor:
This implementation confirms that the iMac 5K internal eDP interface is fully operational at its native 60Hz refresh rate under Linux when using Wayland compositors. By bypassing kernel-level resolution locks and using native Wayland mode management, this setup achieves full feature parity with macOS display performance, effectively reclaiming the hardware for the open-source ecosystem.
Verified configuration to achieve stable **5120x2880 @ 60Hz** resolution on the **iMac 18,3** (Retina 5K, 27-inch, 2017) using the `amdgpu` driver and KDE Plasma (Wayland).
Environment
- Hardware: iMac 18,3 (Mid-2017) / Radeon Pro 570/575/580
- Display: 27" Retina 5K (Internal eDP)
- Bootloader: OpenCore Legacy Patcher (OCLP) -> GRUB
- OS: EndeavourOS (Arch-based)
- Desktop Environment: KDE Plasma (Wayland session)
- Kernel: 6.x+
Step 1: Kernel Parameter Configuration
The following parameters must be passed via the bootloader to override bandwidth safety checks and ensure stable display initialization:
amdgpu.dc=1 amdgpu.exp_res_limit=1 video=eDP-1:2560x1440@60e
- amdgpu.dc=1: Enables the Display Core engine.
- amdgpu.exp_res_limit=1: Lifts the software cap on maximum pixel clock.
- video=eDP-1:2560x1440@60e: Forces a 1440p "bridge" mode at boot to prevent black-screen failstates during TCON handshake before the high-res buffer is initialized.
Step 2: Native Mode Injection (Wayland)
kscreen-doctor successfully injects the native 5K mode into the Wayland compositor:
kscreen-doctor output.eDP-1.addCustomMode.5120.2880.60000.full
kscreen-doctor output.eDP-1.<MODE_ID>
Results
- Native Resolution: 5120x2880 (Active and verified).
- Refresh Rate: 60.00 Hz (Stable without flickering).
- Aspect Ratio: Correct 16:9; no stretching, "stretched desktop" issues, or tiling artifacts.
- Performance: Full hardware acceleration maintained under the amdgpu stack.
Conclusion
This implementation confirms that the iMac 5K internal eDP interface is fully operational at its native 60Hz refresh rate under Linux when using Wayland compositors. By bypassing kernel-level resolution locks and using native Wayland mode management, this setup achieves full feature parity with macOS display performance, effectively reclaiming the hardware for the open-source ecosystem.
So unfortunately it seems all the above solutions to enable 5K (both on X11 and Wayland) are not valid as "they only make the desktop render at 5120x2880, which then gets squeezed into 3840x2160 which remains the actual display resolution".
"I'm afraid there is no avoiding reverse-engineering the Windows driver to see what it does to enable 5K. Or maybe someone will figure out from just the debug log why the second connector is being turned off. Unfortunately, I don't have enough expertise to do these things myself."
see here for more details: https://gitlab.freedesktop.org/drm/amd/-/issues/4455#note_3369545
Also, a cautionary note about using AI chatbots to help troubleshoot technical problems, as one person on gitlab has done. It can sound very exciting - but also be completely wrong!
Edit: there seems to be a difference between Navi (2020) and Polaris (2019 and earlier) iMacs. Possibly Polaris does work at 5K, but Navi doesn't due to changes in the TCON controller.
"I'm afraid there is no avoiding reverse-engineering the Windows driver to see what it does to enable 5K. Or maybe someone will figure out from just the debug log why the second connector is being turned off. Unfortunately, I don't have enough expertise to do these things myself."
see here for more details: https://gitlab.freedesktop.org/drm/amd/-/issues/4455#note_3369545
Also, a cautionary note about using AI chatbots to help troubleshoot technical problems, as one person on gitlab has done. It can sound very exciting - but also be completely wrong!
Edit: there seems to be a difference between Navi (2020) and Polaris (2019 and earlier) iMacs. Possibly Polaris does work at 5K, but Navi doesn't due to changes in the TCON controller.
Last edited:
You make a good point about AI. It's important to vet everything it says.
Differences between 2020 iMac's Navi GPUs and the older iMacs Polaris were mentioned in an earlier post in this thread. The newer Navi GPUs apparently support DP 1.4 and can send a single 5k stream to the display, the older 5k iMacs sent two difference streams to two different sides of the display. It would be ironic if Linux supported Apple's two display hack but not the one 5k Mac that can directly support a 5k video stream.
One further potential issue with the 2020 iMac is the T2. I have heard that the people are experiencing issues with some of the functionality implemented by the T2 such as the sound.
Possibly 'quiet splash video=eDP-1:2560x1440MR@60e video=DP-1:2560x1440MR@60e' in the kernel command line (remember to sudo update-grub afterwards) may work depending on if the compositor of the desktop environment (KDE, Gnome, etc.) can handle stiching those together.
I am reading that KDE are actively improving their tile stiching support. Not sure what's happening on Gnome.
I am reading that KDE are actively improving their tile stiching support. Not sure what's happening on Gnome.