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#1 2026-02-14 12:20:35

nikolas777
Member
Registered: 2026-02-14
Posts: 5

2017 iMac 5K not displaying in full resolution under Wayland

Hello everyone,

Recently I installed Arch Linux in a dual-boot setup alongside the OCLPed macOS on my 2017 iMac 27" with the 5K display. Most things work as expected, except the display.

I added 2 boot entries for Arch in systemd-boot:
one regular "Arch"

options root=LABEL=ArchRoot rw lang=de init=/usr/lib/systemd/systemd locale=de_DE.UTF-8 brcmfmac.feature_disable=0x82000

and one "Arch-5k" with some additional parameters

options root=LABEL=ArchRoot rw lang=de init=/usr/lib/systemd/systemd locale=de_DE.UTF-8 brcmfmac.feature_disable=0x82000 radeon.si_support=0 radeon.cik_support=0 amdgpu.dc=1 amdgpu.mst=1

When I select my Linux EFI Boot via the OpenCore boot picker, I get the following results:
- systemd-boot menu has a more "pixelated" font (just like on a non-HiDPI screen)
- Booting Arch Linux with it results in a 5K tty at first, shortly after that the screen gets stretched on the X-axis (I assume double the width)
- SDDM and Plasma graphical sessions are stretched in width, depending on the resolution/server with huge black bars at the top and bottom
- maximum resolution of 3200x1800 selectable (4K is an option, but applying it doesn't work)
- NO difference between regular and 5k boot entry and Wayland or X11

via iMac's internal EFI boot picker:
- font in systemd-boot is some higher res font
- TTY always at about 4k resolution, but no stretching in boot progress or X11/Wayland
- Wayland limited at 4k in any boot config
- on X11 I can get 5K resolution to work with those xrandr commands:

$ xrandr --newmode "5120x2880"  1276.50  5120 5560 6128 7136  2880 2883 2888 2982 -hsync +vsync
$ xrandr --addmode eDP-1 "5120x2880"
$ xrandr --output eDP-1 --mode 5120x2880 --pos 0x0 --primary

Though the supposed 5K don't look as crisp and just slightly blurry.


Is there a way to get proper 5K resolution working under Wayland?


Thanks in advance,
nikolas777

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#2 2026-02-14 15:39:19

seth
Member
From: Don't DM me only for attention
Registered: 2012-09-03
Posts: 73,197

Re: 2017 iMac 5K not displaying in full resolution under Wayland

Let's first see what's there:

lspci -k
for OUT in /sys/class/drm/card*; do echo $OUT; edid-decode $OUT/edid; echo "================="; done

You'll need https://archlinux.org/packages/extra/x86_64/v4l-utils/

Though the supposed 5K don't look as crisp and just slightly blurry.

You can try either of

# 5120x2880 @ 60.000 Hz Reduced Blank (CVT) field rate 59.993 Hz; hsync: 177.699 kHz; pclk: 938.25 MHz
Modeline "5120x2880_60.00_rb1"  938.25  5120 5168 5200 5280  2880 2883 2888 2962 +hsync -vsync

# 5120x2880 @ 60.000 Hz Reduced Blank (CVT) field rate 60.000 Hz; hsync: 177.720 kHz; pclk: 924.14 MHz
Modeline "5120x2880_60.00_rb2"  924.14  5120 5128 5160 5200  2880 2948 2956 2962 +hsync -vsync

How to upload text · How to boot w/o GUI · Disable Windows Fast-Start! · Fix your xinitrc

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#3 2026-02-17 16:19:20

nikolas777
Member
Registered: 2026-02-14
Posts: 5

Re: 2017 iMac 5K not displaying in full resolution under Wayland

seth wrote:

Let's first see what's there:

lspci -k
$ lspci -k
00:00.0 Host bridge: Intel Corporation Xeon E3-1200 v6/7th Gen Core Processor Host Bridge/DRAM Registers (rev 05)
        DeviceName: SATA
        Subsystem: Apple Inc. Device 0180
        Kernel driver in use: skl_uncore
00:01.0 PCI bridge: Intel Corporation 6th-10th Gen Core Processor PCIe Controller (x16) (rev 05)
        Subsystem: Apple Inc. Device 0180
        Kernel driver in use: pcieport
        Kernel modules: shpchp
00:14.0 USB controller: Intel Corporation 100 Series/C230 Series Chipset Family USB 3.0 xHCI Controller (rev 31)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: xhci_hcd
        Kernel modules: xhci_pci
00:16.0 Communication controller: Intel Corporation 100 Series/C230 Series Chipset Family MEI Controller #1 (rev 31)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: mei_me
        Kernel modules: mei_me
00:17.0 SATA controller: Intel Corporation Q170/Q150/B150/H170/H110/Z170/CM236 Chipset SATA Controller [AHCI Mode] (rev 31)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: ahci
        Kernel modules: ahci
00:1b.0 PCI bridge: Intel Corporation 100 Series/C230 Series Chipset Family PCI Express Root Port #17 (rev f1)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: pcieport
        Kernel modules: shpchp
00:1c.0 PCI bridge: Intel Corporation 100 Series/C230 Series Chipset Family PCI Express Root Port #1 (rev f1)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: pcieport
        Kernel modules: shpchp
00:1c.1 PCI bridge: Intel Corporation 100 Series/C230 Series Chipset Family PCI Express Root Port #2 (rev f1)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: pcieport
        Kernel modules: shpchp
00:1c.4 PCI bridge: Intel Corporation 100 Series/C230 Series Chipset Family PCI Express Root Port #5 (rev f1)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: pcieport
        Kernel modules: shpchp
00:1f.0 ISA bridge: Intel Corporation Z170 Chipset LPC/eSPI Controller (rev 31)
        Subsystem: Intel Corporation Device 7270
00:1f.2 Memory controller: Intel Corporation 100 Series/C230 Series Chipset Family Power Management Controller (rev 31)
        Subsystem: Intel Corporation Device 7270
00:1f.3 Audio device: Intel Corporation 100 Series/C230 Series Chipset Family HD Audio Controller (rev 31)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: snd_hda_intel
        Kernel modules: snd_soc_avs, snd_hda_intel
00:1f.4 SMBus: Intel Corporation 100 Series/C230 Series Chipset Family SMBus (rev 31)
        Subsystem: Intel Corporation Device 7270
        Kernel driver in use: i801_smbus
        Kernel modules: i2c_i801
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 470/480/570/570X/580/580X/590] (rev c0)
        Subsystem: Apple Inc. Radeon Pro 580
        Kernel driver in use: amdgpu
        Kernel modules: amdgpu
01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere HDMI Audio [Radeon RX 470/480 / 570/580/590]
        Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere HDMI Audio [Radeon RX 470/480 / 570/580/590]
        Kernel driver in use: snd_hda_intel
        Kernel modules: snd_hda_intel
02:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller SM961/PM961/SM963
        Subsystem: Samsung Electronics Co Ltd SM963 2.5" NVMe PCIe SSD
        Kernel driver in use: nvme
        Kernel modules: nvme
03:00.0 Network controller: Broadcom Inc. and subsidiaries BCM43602 802.11ac Wireless LAN SoC (rev 01)
        Subsystem: Apple Inc. Device 016f
        Kernel driver in use: brcmfmac
        Kernel modules: brcmfmac
04:00.0 Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM57766 Gigabit Ethernet PCIe (rev 01)
        Subsystem: Broadcom Inc. and subsidiaries NetXtreme BCM57766 Gigabit Ethernet PCIe
        Kernel driver in use: tg3
        Kernel modules: tg3
04:00.1 SD Host controller: Broadcom Inc. and subsidiaries BCM57765/57785 SDXC/MMC Card Reader (rev 01)
        Subsystem: Broadcom Inc. and subsidiaries Device 0000
        Kernel driver in use: sdhci-pci
        Kernel modules: sdhci_pci
05:00.0 PCI bridge: Intel Corporation DSL6540 Thunderbolt 3 Bridge [Alpine Ridge 4C 2015] (rev 02)
        Subsystem: Intel Corporation Device 0000
        Kernel driver in use: pcieport
        Kernel modules: shpchp
06:00.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
        Subsystem: Intel Corporation Device 0000
        Kernel driver in use: pcieport
        Kernel modules: shpchp
06:01.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
        Subsystem: Intel Corporation Device 0000
        Kernel driver in use: pcieport
        Kernel modules: shpchp
06:02.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
        Subsystem: Intel Corporation Device 0000
        Kernel driver in use: pcieport
        Kernel modules: shpchp
06:04.0 PCI bridge: Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02)
        Subsystem: Intel Corporation Device 0000
        Kernel driver in use: pcieport
        Kernel modules: shpchp
07:00.0 System peripheral: Intel Corporation JHL6540 Thunderbolt 3 NHI (C step) [Alpine Ridge 4C 2016] (rev 02)
        Subsystem: Intel Corporation Device 0000
        Kernel driver in use: thunderbolt
        Kernel modules: thunderbolt
08:00.0 USB controller: Intel Corporation JHL6540 Thunderbolt 3 USB Controller (C step) [Alpine Ridge 4C 2016] (rev 02)
        Subsystem: Intel Corporation Device 0000
        Kernel driver in use: xhci_hcd
        Kernel modules: xhci_pci
seth wrote:
for OUT in /sys/class/drm/card*; do echo $OUT; edid-decode $OUT/edid; echo "================="; done
$ for OUT in /sys/class/drm/card*; do echo $OUT; edid-decode $OUT/edid; echo "================="; done
/sys/class/drm/card1
/sys/class/drm/card1/edid: No such file or directory
=================
/sys/class/drm/card1-DP-1
EDID of '/sys/class/drm/card1-DP-1/edid' was empty.
=================
/sys/class/drm/card1-DP-2
EDID of '/sys/class/drm/card1-DP-2/edid' was empty.
=================
/sys/class/drm/card1-DP-3
EDID of '/sys/class/drm/card1-DP-3/edid' was empty.
=================
/sys/class/drm/card1-eDP-1
edid-decode (hex):

00 ff ff ff ff ff ff 00 06 10 11 ae 28 ad e9 6b
0a 1a 01 04 b5 3c 22 78 20 0a 21 ae 52 41 b2 26
0d 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 4d d0 00 a0 f0 70 3e 80 30 20
35 00 55 50 21 00 00 1a 56 5e 00 a0 a0 a0 29 50
30 20 35 00 55 50 21 00 00 1a 00 00 00 fc 00 69
4d 61 63 0a 20 20 20 20 20 20 20 20 00 00 00 ff
00 38 31 43 39 31 31 37 32 38 41 44 32 39 01 25

02 03 27 c0 23 09 07 07 83 01 00 00 70 fa 10 00
00 12 76 31 fc 78 fb ff 02 10 88 62 d3 69 fa 10
00 fa f8 f8 fe ff ff cd 91 80 a0 c0 08 34 70 30
20 35 00 55 50 21 00 00 1a 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 3e

----------------

Block 0, Base EDID:
  EDID Structure Version & Revision: 1.4
  Vendor & Product Identification:
    Manufacturer: APP
    Model: 44561
    Serial Number: 1810476328 (0x6be9ad28)
    Made in: week 10 of 2016
  Basic Display Parameters & Features:
    Digital display
    Bits per primary color channel: 10
    DisplayPort interface
    Maximum image size: 60 cm x 34 cm
    Gamma: 2.20
    DPMS levels: Off
    Supported color formats: RGB 4:4:4
    First detailed timing does not include the native pixel format and preferred refresh rate
  Color Characteristics:
    Red  : 0.6796, 0.3203
    Green: 0.2558, 0.6972
    Blue : 0.1484, 0.0527
    White: 0.3125, 0.3291
  Established Timings I & II: none
  Standard Timings: none
  Detailed Timing Descriptors:
    DTD 1:  3840x2160   59.996625 Hz  16:9    133.312 kHz    533.250000 MHz (597 mm x 336 mm)
                 Hfront   48 Hsync  32 Hback   80 Hpol P
                 Vfront    3 Vsync   5 Vback   54 Vpol N
    DTD 2:  2560x1440   59.950550 Hz  16:9     88.787 kHz    241.500000 MHz (597 mm x 336 mm)
                 Hfront   48 Hsync  32 Hback   80 Hpol P
                 Vfront    3 Vsync   5 Vback   33 Vpol N
    Display Product Name: 'iMac'
    Display Product Serial Number: '81C911728AD29'
  Extension blocks: 1
Checksum: 0x25

----------------

Block 1, CTA-861 Extension Block:
  Revision: 3
  Underscans IT Video Formats by default
  Basic audio support
  Native detailed modes: 0
  Audio Data Block:
    Linear PCM:
      Max channels: 2
      Supported sample rates (kHz): 48 44.1 32
      Supported sample sizes (bits): 24 20 16
  Speaker Allocation Data Block:
    FL/FR - Front Left/Right
  Vendor-Specific Data Block (Apple), OUI 00-10-FA:
    00 12 76 31 fc 78 fb ff 02 10 88 62 d3          '..v1.x.....b.'
  Vendor-Specific Data Block (Apple), OUI 00-10-FA:
    fa f8 f8 fe ff ff                               '......'
  Detailed Timing Descriptors:
    DTD 3:  3200x1800   59.981809 Hz  16:9    111.086 kHz    373.250000 MHz (597 mm x 336 mm)
                 Hfront   48 Hsync  32 Hback   80 Hpol P
                 Vfront    3 Vsync   5 Vback   44 Vpol N
Checksum: 0x3e  Unused space in Extension Block: 70 bytes
=================

Actually, I tried to get the EDIDs from macOS via BetterDisplay and apply them. Though, both EDID (one from OS, other from I2C directly) don't work as-is when loading them with "drm.edid_firmware=eDP-1:edid/[FILE].bin" (and of course integrating them in initram file). It either results in blackscreen or stretching of screen again.
Checking them with edid-decode results in failure for both of them:

$ edid-decode iMac5K_I2C_EDID.bin --check
edid-decode (hex):

00 ff ff ff ff ff ff 00 06 10 12 ae 28 ad e9 6b
0a 1a 01 04 b5 1e 22 78 22 0a 21 ae 52 41 b2 26
0d 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 c5 bc 00 a0 a0 40 52 b0 30 20
3a 00 2b 50 11 00 00 1a 8f 7a 00 a0 80 00 42 90
30 20 3a 00 2b 50 11 00 00 1a 00 00 00 fc 00 69
4d 61 63 0a 20 20 20 20 20 20 20 20 00 00 00 ff
00 38 31 43 39 31 31 37 32 38 41 44 32 39 01 94

70 13 79 03 00 12 00 16 82 10 00 00 ff 09 3f 0b
00 00 00 00 00 41 50 50 13 ae 28 ad e9 42 03 00
3c 4c d0 00 04 ff 0e 9f 00 2f 80 1f 00 6f 08 3d
00 02 00 04 00 cc 91 00 04 7f 0c 9f 00 2f 80 1f
00 07 07 33 00 02 00 04 00 55 5e 00 04 ff 09 9f
00 2f 80 1f 00 9f 05 28 00 02 00 04 00 7f 81 18
fa 10 00 01 01 00 12 76 31 fc 78 fb ff 02 10 88
62 d3 fa f8 f8 fe ff ff 00 00 00 00 00 00 92 90

----------------

Block 0, Base EDID:
  EDID Structure Version & Revision: 1.4
  Vendor & Product Identification:
    Manufacturer: APP
    Model: 44562
    Serial Number: 1810476328 (0x6be9ad28)
    Made in: week 10 of 2016
  Basic Display Parameters & Features:
    Digital display
    Bits per primary color channel: 10
    DisplayPort interface
    Maximum image size: 30 cm x 34 cm
    Gamma: 2.20
    DPMS levels: Off
    Supported color formats: RGB 4:4:4
    First detailed timing includes the native pixel format and preferred refresh rate
  Color Characteristics:
    Red  : 0.6796, 0.3203
    Green: 0.2558, 0.6972
    Blue : 0.1484, 0.0527
    White: 0.3125, 0.3291
  Established Timings I & II: none
  Standard Timings: none
  Detailed Timing Descriptors:
    DTD 1:  2560x2880   59.981580 Hz   8:9    177.665 kHz    483.250000 MHz (299 mm x 336 mm)
                 Hfront   48 Hsync  32 Hback   80 Hpol P
                 Vfront    3 Vsync  10 Vback   69 Vpol N
    DTD 2:  2048x2304   59.956506 Hz   8:9    142.097 kHz    313.750000 MHz (299 mm x 336 mm)
                 Hfront   48 Hsync  32 Hback   80 Hpol P
                 Vfront    3 Vsync  10 Vback   53 Vpol N
    Display Product Name: 'iMac'
    Display Product Serial Number: '81C911728AD29'
  Extension blocks: 1
Checksum: 0x94

----------------

Block 1, DisplayID Extension Block:
  Version: 1.3
  Extension Count: 0
  Display Product Type: Standalone display device
  Tiled Display Topology Data Block (0x12):
    Capabilities:
      Behavior if it is the only tile: Image is scaled to fit the entire tiled display
      Behavior if more than one tile and fewer than total number of tiles: Undefined
    Tiled display consists of a single physical display enclosure
    Num horizontal tiles: 2 Num vertical tiles: 1
    Tile location: 0, 0
    Tile resolution: 2560x2880
    Tiled Display Manufacturer/Vendor ID: APP
    Tiled Display Product ID Code: 44563
    Tiled Display Serial Number: 1122610472
  Video Timing Modes Type 1 - Detailed Timings Data Block:
    DTD:  3840x2160   59.996625 Hz  16:9    133.312 kHz    533.250000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol P
               Vfront    3 Vsync   5 Vback   54 Vpol N
    DTD:  3200x1800   59.981809 Hz  16:9    111.086 kHz    373.250000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol P
               Vfront    3 Vsync   5 Vback   44 Vpol N
    DTD:  2560x1440   59.950550 Hz  16:9     88.787 kHz    241.500000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol P
               Vfront    3 Vsync   5 Vback   33 Vpol N
  Vendor-Specific Data Block (0x7f) (Apple), OUI 00-10-FA:
    Type: BLC Info/Corrections, Version: 1
    00 12 76 31 fc 78 fb ff 02 10 88 62 d3 fa f8 f8 '..v1.x.....b....'
    fe ff ff                                        '...'
  Checksum: 0x92
Checksum: 0x90

----------------

edid-decode 1.32.0

Warnings:

Block 1, DisplayID Extension Block:
  Vendor-Specific Data Block (0x7f) (Apple), OUI 00-10-FA: Expected PNP ID but found OUI.

Failures:

Block 1, DisplayID Extension Block:
  Vendor-Specific Data Block (0x7f) (Apple), OUI 00-10-FA: Endian-ness (le) of OUI is different than expected (be).
EDID:
  DisplayID: Missing DisplayID Product Identification Data Block.
  DisplayID: Missing DisplayID Display Parameters Data Block.
  DisplayID: DisplayID expects at least one preferred timing.

EDID conformity: FAIL
$ edid-decode iMac5K_EDID.bin --check
edid-decode (hex):

00 ff ff ff ff ff ff 00 06 10 13 ae 28 ad e9 6b
0a 1a 01 04 b5 3c 22 78 20 0a 21 ae 52 41 b2 26
0d 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 00 00 00 10 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 10 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 fc 00 69
4d 61 63 0a 20 20 20 20 20 20 20 20 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 02 8b

70 13 79 03 00 03 00 14 80 6e 01 84 ff 13 9f 00
2f 80 1f 00 3f 0b 51 00 02 00 04 00 7f 81 18 fa
10 00 01 01 00 12 76 31 fc 78 fb ff 02 10 88 62
d3 fa f8 f8 fe ff ff 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 c7 90

70 13 79 03 00 03 01 50 53 ec 00 04 ff 0f 9f 00
2f 00 1f 00 ff 08 41 00 02 00 04 00 4c d0 00 04
ff 0e 9f 00 2f 00 1f 00 6f 08 3d 00 02 00 04 00
cc 91 00 04 7f 0c 9f 00 2f 00 1f 00 07 07 33 00
02 00 04 00 55 5e 00 04 ff 09 9f 00 2f 00 1f 00
9f 05 28 00 02 00 04 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 1f 90

----------------

Block 0, Base EDID:
  EDID Structure Version & Revision: 1.4
  Vendor & Product Identification:
    Manufacturer: APP
    Model: 44563
    Serial Number: 1810476328 (0x6be9ad28)
    Made in: week 10 of 2016
  Basic Display Parameters & Features:
    Digital display
    Bits per primary color channel: 10
    DisplayPort interface
    Maximum image size: 60 cm x 34 cm
    Gamma: 2.20
    DPMS levels: Off
    Supported color formats: RGB 4:4:4
    First detailed timing does not include the native pixel format and preferred refresh rate
  Color Characteristics:
    Red  : 0.6796, 0.3203
    Green: 0.2558, 0.6972
    Blue : 0.1484, 0.0527
    White: 0.3125, 0.3291
  Established Timings I & II: none
  Standard Timings: none
  Detailed Timing Descriptors:
    Dummy Descriptor:
    Dummy Descriptor:
    Display Product Name: 'iMac'
    Empty Descriptor
  Extension blocks: 2
Checksum: 0x8b

----------------

Block 1, DisplayID Extension Block:
  Version: 1.3
  Extension Count: 0
  Display Product Type: Standalone display device
  Video Timing Modes Type 1 - Detailed Timings Data Block:
    DTD:  5120x2880   59.992864 Hz  16:9    177.699 kHz    938.250000 MHz (aspect 16:9, no 3D stereo, preferred)
               Hfront   48 Hsync  32 Hback   80 Hpol P
               Vfront    3 Vsync   5 Vback   74 Vpol N
  Vendor-Specific Data Block (0x7f) (Apple), OUI 00-10-FA:
    Type: BLC Info/Corrections, Version: 1
    00 12 76 31 fc 78 fb ff 02 10 88 62 d3 fa f8 f8 '..v1.x.....b....'
    fe ff ff                                        '...'
  Checksum: 0xc7
Checksum: 0x90

----------------

Block 2, DisplayID Extension Block:
  Version: 1.3
  Extension Count: 0
  Video Timing Modes Type 1 - Detailed Timings Data Block:
    DTD:  4096x2304   59.979855 Hz  16:9    142.152 kHz    605.000000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol N
               Vfront    3 Vsync   5 Vback   58 Vpol N
    DTD:  3840x2160   59.996625 Hz  16:9    133.312 kHz    533.250000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol N
               Vfront    3 Vsync   5 Vback   54 Vpol N
    DTD:  3200x1800   59.981809 Hz  16:9    111.086 kHz    373.250000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol N
               Vfront    3 Vsync   5 Vback   44 Vpol N
    DTD:  2560x1440   59.950550 Hz  16:9     88.787 kHz    241.500000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol N
               Vfront    3 Vsync   5 Vback   33 Vpol N
  Checksum: 0x1f
Checksum: 0x90

----------------

edid-decode 1.32.0

Warnings:

Block 1, DisplayID Extension Block:
  Vendor-Specific Data Block (0x7f) (Apple), OUI 00-10-FA: Expected PNP ID but found OUI.
EDID:
  No Native Video Resolution was defined.

Failures:

Block 0, Base EDID:
  Standard Timings: Missing preferred timing.
  Empty Descriptor: Use Dummy Descriptor instead of all zeroes.
Block 1, DisplayID Extension Block:
  Expected 0 DisplayID Extension Block, but got 1.
  Vendor-Specific Data Block (0x7f) (Apple), OUI 00-10-FA: Endian-ness (le) of OUI is different than expected (be).
Block 2, DisplayID Extension Block:
  Product Type should be 0 in extension block.
EDID:
  DisplayID: Missing DisplayID Display Parameters Data Block.

EDID conformity: FAIL

Would it be worth trying to install Windows via Bootcamp, get another (hopefully correct) EDID and apply it in Linux?

For the Modelines, I will test them rn - but I guess that is again a X11 only solution (which is not optimal since Plasma won't support X11 for long).

Offline

#4 2026-02-17 16:33:04

nikolas777
Member
Registered: 2026-02-14
Posts: 5

Re: 2017 iMac 5K not displaying in full resolution under Wayland

nikolas777 wrote:

For the Modelines, I will test them rn - but I guess that is again a X11 only solution (which is not optimal since Plasma won't support X11 for long).

So testing those new modes didn't really make a difference to my eyes. I noticed though, that in all 3 modes I get some "fuzzy" lines glitching at the bottom right corner. It's looking a bit like those most bottom lines on an analog video tape.

Offline

#5 2026-02-17 21:24:37

seth
Member
From: Don't DM me only for attention
Registered: 2012-09-03
Posts: 73,197

Re: 2017 iMac 5K not displaying in full resolution under Wayland

You've a GCN 4.0 chip, "radeon.si_support=0 radeon.cik_support=0" should™ be pointless - did you get ths from https://forums.linuxmint.com/viewtopic. … 1#p2732127 ?
Also https://forums.macrumors.com/threads/ca … k.2459774/
https://khronokernel.com/macos/2021/12/08/5K-UEFI.html

The problem seems to be that those are actually two 2560x2880 tiles - hence the non-conformant EDIDs from MacOS
Also injecting a custom EDID (no matter where you get that from) is not going to help you.
The custom bootcamp driver works because

The main change Apple/AMD added with this driver was the ability to force the Display Controller back into the dual DisplayPort Stream (ae03 ID).

The moment you load grub (or any linux bootloader or UKI) the monitor/output will change into the compatibility mode where you won't get 5k out of it no matter what sad

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#6 2026-02-20 00:50:42

nikolas777
Member
Registered: 2026-02-14
Posts: 5

Re: 2017 iMac 5K not displaying in full resolution under Wayland

seth wrote:

You've a GCN 4.0 chip, "radeon.si_support=0 radeon.cik_support=0" should™ be pointless - did you get ths from https://forums.linuxmint.com/viewtopic. … 1#p2732127 ?

Yeah, I did.

seth wrote:

The moment you load grub (or any linux bootloader or UKI) the monitor/output will change into the compatibility mode where you won't get 5k out of it no matter what sad

Which is true, when I load the bootloader via the Apple EFI (where I get a 4K output from start to finish). When I use the OpenCore EFI to boot into the Linux bootloader, I get quite different results.
After selecting Arch in systemd-boot I get a 5K output, right before the AMD driver loads up. Only after the GPU driver loads up, I get the stretched view. I noticed a few errors when booting up, related to DP(?) and amdgpu:

[  +0,798730] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1122: core_link_write_dpcd (DP_DOWNSPREAD_CTRL) failed
[  +0,020620] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1127: core_link_write_dpcd (DP_LANE_COUNT_SET) failed
[  +0,020690] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1155: core_link_write_dpcd (DP_LINK_BW_SET) failed
[  +0,501311] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1122: core_link_write_dpcd (DP_DOWNSPREAD_CTRL) failed
[  +0,020685] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1127: core_link_write_dpcd (DP_LANE_COUNT_SET) failed
[  +0,020690] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1155: core_link_write_dpcd (DP_LINK_BW_SET) failed
[  +0,550624] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1122: core_link_write_dpcd (DP_DOWNSPREAD_CTRL) failed
[  +0,020686] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1127: core_link_write_dpcd (DP_LANE_COUNT_SET) failed
[  +0,020689] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1155: core_link_write_dpcd (DP_LINK_BW_SET) failed
[  +0,598627] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1122: core_link_write_dpcd (DP_DOWNSPREAD_CTRL) failed
[  +0,020685] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1127: core_link_write_dpcd (DP_LANE_COUNT_SET) failed
[  +0,020689] amdgpu 0000:01:00.0: [drm] *ERROR* dpcd_set_link_settings:1155: core_link_write_dpcd (DP_LINK_BW_SET) failed
[  +0,230625] amdgpu 0000:01:00.0: [drm] enabling link 1 failed: 15

And 

$ for OUT in /sys/class/drm/card*; do echo $OUT; edid-decode

gives a different result:

$OUT/edid; echo "================="; done
/sys/class/drm/card1
/sys/class/drm/card1/edid: No such file or directory
=================
/sys/class/drm/card1-DP-1
EDID of '/sys/class/drm/card1-DP-1/edid' was empty.
=================
/sys/class/drm/card1-DP-2
EDID of '/sys/class/drm/card1-DP-2/edid' was empty.
=================
/sys/class/drm/card1-DP-3
EDID of '/sys/class/drm/card1-DP-3/edid' was empty.
=================
/sys/class/drm/card1-eDP-1
edid-decode (hex):

00 ff ff ff ff ff ff 00 06 10 12 ae 28 ad e9 6b
0a 1a 01 04 b5 1e 22 78 22 0a 21 ae 52 41 b2 26
0d 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 c5 bc 00 a0 a0 40 52 b0 30 20
3a 00 2b 50 11 00 00 1a 8f 7a 00 a0 80 00 42 90
30 20 3a 00 2b 50 11 00 00 1a 00 00 00 fc 00 69
4d 61 63 0a 20 20 20 20 20 20 20 20 00 00 00 ff
00 38 31 43 39 31 31 37 32 38 41 44 32 39 01 94

70 13 79 03 00 12 00 16 82 10 00 00 ff 09 3f 0b
00 00 00 00 00 41 50 50 13 ae 28 ad e9 42 03 00
3c 4c d0 00 04 ff 0e 9f 00 2f 80 1f 00 6f 08 3d
00 02 00 04 00 cc 91 00 04 7f 0c 9f 00 2f 80 1f
00 07 07 33 00 02 00 04 00 55 5e 00 04 ff 09 9f
00 2f 80 1f 00 9f 05 28 00 02 00 04 00 7f 81 18
fa 10 00 01 01 00 12 76 31 fc 78 fb ff 02 10 88
62 d3 fa f8 f8 fe ff ff 00 00 00 00 00 00 92 90

----------------

Block 0, Base EDID:
  EDID Structure Version & Revision: 1.4
  Vendor & Product Identification:
    Manufacturer: APP
    Model: 44562
    Serial Number: 1810476328 (0x6be9ad28)
    Made in: week 10 of 2016
  Basic Display Parameters & Features:
    Digital display
    Bits per primary color channel: 10
    DisplayPort interface
    Maximum image size: 30 cm x 34 cm
    Gamma: 2.20
    DPMS levels: Off
    Supported color formats: RGB 4:4:4
    First detailed timing includes the native pixel format and preferred refresh rate
  Color Characteristics:
    Red  : 0.6796, 0.3203
    Green: 0.2558, 0.6972
    Blue : 0.1484, 0.0527
    White: 0.3125, 0.3291
  Established Timings I & II: none
  Standard Timings: none
  Detailed Timing Descriptors:
    DTD 1:  2560x2880   59.981580 Hz   8:9    177.665 kHz    483.250000 MHz (299 mm x 336 mm)
                 Hfront   48 Hsync  32 Hback   80 Hpol P
                 Vfront    3 Vsync  10 Vback   69 Vpol N
    DTD 2:  2048x2304   59.956506 Hz   8:9    142.097 kHz    313.750000 MHz (299 mm x 336 mm)
                 Hfront   48 Hsync  32 Hback   80 Hpol P
                 Vfront    3 Vsync  10 Vback   53 Vpol N
    Display Product Name: 'iMac'
    Display Product Serial Number: '81C911728AD29'
  Extension blocks: 1
Checksum: 0x94

----------------

Block 1, DisplayID Extension Block:
  Version: 1.3
  Extension Count: 0
  Display Product Type: Standalone display device
  Tiled Display Topology Data Block (0x12):
    Capabilities:
      Behavior if it is the only tile: Image is scaled to fit the entire tiled display
      Behavior if more than one tile and fewer than total number of tiles: Undefined
    Tiled display consists of a single physical display enclosure
    Num horizontal tiles: 2 Num vertical tiles: 1
    Tile location: 0, 0
    Tile resolution: 2560x2880
    Tiled Display Manufacturer/Vendor ID: APP
    Tiled Display Product ID Code: 44563
    Tiled Display Serial Number: 1122610472
  Video Timing Modes Type 1 - Detailed Timings Data Block:
    DTD:  3840x2160   59.996625 Hz  16:9    133.312 kHz    533.250000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol P
               Vfront    3 Vsync   5 Vback   54 Vpol N
    DTD:  3200x1800   59.981809 Hz  16:9    111.086 kHz    373.250000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol P
               Vfront    3 Vsync   5 Vback   44 Vpol N
    DTD:  2560x1440   59.950550 Hz  16:9     88.787 kHz    241.500000 MHz (aspect 16:9, no 3D stereo)
               Hfront   48 Hsync  32 Hback   80 Hpol P
               Vfront    3 Vsync   5 Vback   33 Vpol N
  Vendor-Specific Data Block (0x7f) (Apple), OUI 00-10-FA:
    Type: BLC Info/Corrections, Version: 1
    00 12 76 31 fc 78 fb ff 02 10 88 62 d3 fa f8 f8 '..v1.x.....b....'
    fe ff ff                                        '...'
  Checksum: 0x92
Checksum: 0x90
=================

Booting the OC->systemd-boot way, I can get a correct 5K output on Wayland with the nomodeset kernel parameter. From what I gather, there is a problem with the AMD driver, which makes things not work the correct way.

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#7 2026-02-20 09:37:46

seth
Member
From: Don't DM me only for attention
Registered: 2012-09-03
Posts: 73,197

Re: 2017 iMac 5K not displaying in full resolution under Wayland

  Detailed Timing Descriptors:
    DTD 1:  2560x2880   59.981580 Hz   8:9    177.665 kHz    483.250000 MHz (299 mm x 336 mm)
                 Hfront   48 Hsync  32 Hback   80 Hpol P
                 Vfront    3 Vsync  10 Vback   69 Vpol N
…
  Tiled Display Topology Data Block (0x12):
    Capabilities:
      Behavior if it is the only tile: Image is scaled to fit the entire tiled display
      Behavior if more than one tile and fewer than total number of tiles: Undefined
    Tiled display consists of a single physical display enclosure
    Num horizontal tiles: 2 Num vertical tiles: 1
    Tile location: 0, 0
    Tile resolution: 2560x2880
    Tiled Display Manufacturer/Vendor ID: APP
    Tiled Display Product ID Code: 44563
    Tiled Display Serial Number: 1122610472

https://gitlab.freedesktop.org/drm/amd/-/issues/4455
Though about the workaround there 

Though the supposed 5K don't look as crisp and just slightly blurry.

And it's also now what I'd expect a solution could look like (you'd expect to get two outputs and arrange them next to each other) so this will most likely just trigger the 3840x2160 mode scaling.

If you copy the edid you get w/o amdgpu and inject it at runtime (before starting anything wayland) and then just start some wayland compositor, how does that respond?

Interestingly https://gitlab.freedesktop.org/drm/amd/-/issues/3438 has a 5k EDID that looks error-free…
Does http://0x0.st/PuCK.bin work for you?

Edit, also https://gitlab.gnome.org/GNOME/mutter/-/issues/2313

Last edited by seth (2026-02-20 09:39:03)

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#8 2026-02-20 12:47:21

nikolas777
Member
Registered: 2026-02-14
Posts: 5

Re: 2017 iMac 5K not displaying in full resolution under Wayland

seth wrote:

Though about the workaround there 

Though the supposed 5K don't look as crisp and just slightly blurry.

And it's also now what I'd expect a solution could look like (you'd expect to get two outputs and arrange them next to each other) so this will most likely just trigger the 3840x2160 mode scaling.

The workaround "worked" only in the AppleEFI->systemd-boot boot way, and I guess you are right about the compability mode (as again, I get a 4K tty, and 4K X11/Wayland session).
But booting via OC->sd-boot I only get 5K right before amdgpu loads up. The moment amdgpu loads up, I get the stretched screen (even with the kernel parameters set (DC, MST, video=5120x2880...)):

Here is sddm (which should be X11 if I'm not mistaken)
https://pasteboard.co/gHiJjUG8OEAR.jpg
X11 with an 8:9 resolution:
https://pasteboard.co/SuVoNnfHnBEE.jpg
X11 with 16:9 resolution:
https://pasteboard.co/c5RqCfbjHlv7.jpg

Wayland looks the same.
Also I can't change the resolution to 5K at all with this "boot chain". With all the modes from you and from the gitlab issue, I get:

xrandr: Configure crtc 0 failed
seth wrote:

If you copy the edid you get w/o amdgpu and inject it at runtime (before starting anything wayland) and then just start some wayland compositor, how does that respond?

I guess there has been a misunderstanding there: the EDID I got was with amdgpu loaded (albeit with a stretched output), but with OC loaded before systemd-boot. The results I sent before (on 17th Feb) were when booting via AppleEFI directly.
Booting via OC->sd-b and nomodeset I don't get any EDIDs (as there are no DRM devices loaded I guess), but a nice crisp 5K image on tty, X11 and Wayland.
And what do you mean by "inject it at runtime"?

seth wrote:

Does http://0x0.st/PuCK.bin work for you?

If you mean to load it with "drm.edid_firmware" kernel parameter, I tried this one out and I only get a blackscreen when amdgpu loads up (no matter whether it's via AppleEFI or OpenCore).

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#9 2026-02-20 16:08:57

seth
Member
From: Don't DM me only for attention
Registered: 2012-09-03
Posts: 73,197

Re: 2017 iMac 5K not displaying in full resolution under Wayland

I guess there has been a misunderstanding there: the EDID I got was with amdgpu loaded

Hence the idea to blacklist amdgpu and copy that edid (since the one you got via apple doesn't work)
Next to the kernel commandline parameter you can also change the edid by writing into that (pseudo)file, https://wiki.archlinux.org/title/Kernel … s_and_EDID

I tried this one out and I only get a blackscreen when amdgpu loads up

Might be from a slightly different model.

For clarification, those screenshots aren't you only options?
The 3840x2160 failsafe mode works as expected?

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