Actually the problem might just be that the Linux kernel doesn't understand extended vendor-specific display timings. I've decoded your monitor's EDID and it reveals that 3840x2160 30Hz is mentioned:
edid-decode (hex): 00 ff ff ff ff ff ff 00 04 69 a3 28 24 51 00 00 0e 1b 01 03 80 3e 22 78 3a 1c b5 a3 57 4f a0 27 0d 50 54 bf ef 00 d1 c0 81 40 81 80 95 00 b3 00 71 4f 81 c0 01 01 04 74 00 30 f2 70 5a 80 b0 58 8a 00 6d 55 21 00 00 1a 02 3a 80 18 71 38 2d 40 58 2c 45 00 6d 55 21 00 00 1e 00 00 00 fd 00 1e 50 18 a0 1e 00 0a 20 20 20 20 20 20 00 00 00 fc 00 41 53 55 53 20 50 42 32 38 37 51 0a 20 01 83 02 03 2c f1 51 01 02 03 11 12 13 04 14 05 0e 0f 1d 1e 1f 90 20 22 23 09 17 07 83 01 00 00 6d 03 0c 00 20 00 00 3c 20 00 60 01 02 03 56 5e 00 a0 a0 a0 29 50 30 20 35 00 6d 55 21 00 00 1e e2 68 00 a0 a0 40 2e 60 30 20 36 00 6d 55 21 00 00 1a 01 1d 00 bc 52 d0 1e 20 b8 28 55 40 6d 55 21 00 00 1e 8c 0a d0 90 20 40 31 20 0c 40 55 00 6d 55 21 00 00 18 00 00 00 00 00 00 00 00 00 00 00 5e ---------------- EDID version: 1.3 Manufacturer: ACI Model 10403 Serial Number 20772 Made in week 14 of 2017 Digital display Maximum image size: 62 cm x 34 cm Gamma: 2.20 DPMS levels: Off Undefined display color type First detailed timing is preferred timing Color Characteristics Red: 0.6367, 0.3408 Green: 0.3115, 0.6250 Blue: 0.1542, 0.0537 White: 0.3134, 0.3291 Established Timings I & II 720x400 70.082 Hz 9:5 31.467 kHz 28.320 MHz (IBM) 640x480 59.940 Hz 4:3 31.469 kHz 25.175 MHz (DMT) 640x480 66.667 Hz 4:3 35.000 kHz 30.240 MHz (Apple) 640x480 72.809 Hz 4:3 37.861 kHz 31.500 MHz (DMT) 640x480 75.000 Hz 4:3 37.500 kHz 31.500 MHz (DMT) 800x600 56.250 Hz 4:3 35.156 kHz 36.000 MHz (DMT) 800x600 60.317 Hz 4:3 37.879 kHz 40.000 MHz (DMT) 800x600 72.188 Hz 4:3 48.077 kHz 50.000 MHz (DMT) 800x600 75.000 Hz 4:3 46.875 kHz 49.500 MHz (DMT) 832x624 74.551 Hz 4:3 49.726 kHz 57.284 MHz (Apple) 1024x768 60.004 Hz 4:3 48.363 kHz 65.000 MHz (DMT) 1024x768 70.069 Hz 4:3 56.476 kHz 75.000 MHz (DMT) 1024x768 75.029 Hz 4:3 60.023 kHz 78.750 MHz (DMT) 1280x1024 75.025 Hz 5:4 79.976 kHz 135.000 MHz (DMT) Standard Timings 1920x1080 60.000 Hz 16:9 67.500 kHz 148.500 MHz (DMT) 1280x960 60.000 Hz 4:3 60.000 kHz 108.000 MHz (DMT) 1280x1024 60.020 Hz 5:4 63.981 kHz 108.000 MHz (DMT) 1440x900 59.887 Hz 16:10 55.935 kHz 106.500 MHz (DMT) 1680x1050 59.954 Hz 16:10 65.290 kHz 146.250 MHz (DMT) 1152x864 75.000 Hz 4:3 67.500 kHz 108.000 MHz (DMT) 1280x720 60.000 Hz 16:9 45.000 kHz 74.250 MHz (DMT) Detailed mode: Clock 297.000 MHz, 621 mm x 341 mm 3840 4016 4104 4400 (176 88 296) 2160 2168 2178 2250 ( 8 10 72) +hsync -vsync VertFreq: 30.000 Hz, HorFreq: 67.500 kHz Detailed mode: Clock 148.500 MHz, 621 mm x 341 mm 1920 2008 2052 2200 ( 88 44 148) 1080 1084 1089 1125 ( 4 5 36) +hsync +vsync VertFreq: 60.000 Hz, HorFreq: 67.500 kHz Display Range Limits Monitor ranges (GTF): 30-80 Hz V, 24-160 kHz H, max dotclock 300 MHz Display Product Name: ASUS PB287Q Has 1 extension block Checksum: 0x83 ---------------- CTA-861 Extension Block Revision 3 Underscans PC formats by default Basic audio support Supports YCbCr 4:4:4 Supports YCbCr 4:2:2 1 native detailed modes 40 bytes of CTA data blocks Video Data Block 640x480 59.940 Hz 4:3 31.469 kHz 25.175 MHz (VIC 1) 720x480 59.940 Hz 4:3 31.469 kHz 27.000 MHz (VIC 2) 720x480 59.940 Hz 16:9 31.469 kHz 27.000 MHz (VIC 3) 720x576 50.000 Hz 4:3 31.250 kHz 27.000 MHz (VIC 17) 720x576 50.000 Hz 16:9 31.250 kHz 27.000 MHz (VIC 18) 1280x720 50.000 Hz 16:9 37.500 kHz 74.250 MHz (VIC 19) 1280x720 60.000 Hz 16:9 45.000 kHz 74.250 MHz (VIC 4) 1920x1080i 50.000 Hz 16:9 28.125 kHz 74.250 MHz (VIC 20) 1920x1080i 60.000 Hz 16:9 33.750 kHz 74.250 MHz (VIC 5) 1440x480 59.940 Hz 4:3 31.469 kHz 54.000 MHz (VIC 14) 1440x480 59.940 Hz 16:9 31.469 kHz 54.000 MHz (VIC 15) 1440x576 50.000 Hz 4:3 31.250 kHz 54.000 MHz (VIC 29) 1440x576 50.000 Hz 16:9 31.250 kHz 54.000 MHz (VIC 30) 1920x1080 50.000 Hz 16:9 56.250 kHz 148.500 MHz (VIC 31) 1920x1080 60.000 Hz 16:9 67.500 kHz 148.500 MHz (VIC 16, native) 1920x1080 24.000 Hz 16:9 27.000 kHz 74.250 MHz (VIC 32) 1920x1080 30.000 Hz 16:9 33.750 kHz 74.250 MHz (VIC 34) Audio Data Block Linear PCM, max channels 2 Supported sample rates (kHz): 96 48 44.1 32 Supported sample sizes (bits): 24 20 16 Speaker Allocation Data Block Speaker map: FL/FR - Front Left/Right Vendor-Specific Data Block, OUI 0x000c03 (HDMI) Source physical address 2.0.0.0 Maximum TMDS clock: 300 MHz Extended HDMI video details: HDMI VICs: 3840x2160 30.000 Hz 16:9 67.500 kHz 297.000 MHz (HDMI VIC 1) 3840x2160 25.000 Hz 16:9 56.250 kHz 297.000 MHz (HDMI VIC 2) 3840x2160 24.000 Hz 16:9 54.000 kHz 297.000 MHz (HDMI VIC 3) Detailed mode: Clock 241.500 MHz, 621 mm x 341 mm 2560 2608 2640 2720 ( 48 32 80) 1440 1443 1448 1481 ( 3 5 33) +hsync +vsync VertFreq: 59.951 Hz, HorFreq: 88.787 kHz Detailed mode: Clock 268.500 MHz, 621 mm x 341 mm 2560 2608 2640 2720 ( 48 32 80) 1600 1603 1609 1646 ( 3 6 37) +hsync -vsync VertFreq: 59.972 Hz, HorFreq: 98.713 kHz Detailed mode: Clock 74.250 MHz, 621 mm x 341 mm 1280 1720 1760 1980 (440 40 220) 720 725 730 750 ( 5 5 20) +hsync +vsync VertFreq: 50.000 Hz, HorFreq: 37.500 kHz Detailed mode: Clock 27.000 MHz, 621 mm x 341 mm 720 732 796 864 ( 12 64 68) 576 581 586 625 ( 5 5 39) -hsync -vsync VertFreq: 50.000 Hz, HorFreq: 31.250 kHz Checksum: 0x5e ** Package changed: mutter (Ubuntu) => xorg-server (Ubuntu) ** Also affects: linux (Ubuntu) Importance: Undecided Status: New ** Summary changed: - External monitor will not display to 4k + i915 does not expose vendor-specific extended HDMI timings/modes ** Changed in: xorg-server (Ubuntu) Status: Incomplete => New -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1890418 Title: i915 does not expose vendor-specific extended HDMI timings/modes Status in linux package in Ubuntu: Incomplete Status in xorg-server package in Ubuntu: Incomplete Bug description: I have a Toshiba radius 11 laptop which has a 4 k native screen. I have connected an Asus PB287Q 28" external monitor (https://www.asus.com/us/Commercial-Monitors/PB287Q/specifications/) over HDMI which displays the full 4K resolution when running under windows10 but will only reach a maximum resolution of 1920x1080 under ubuntu 20.04, same hardware just dual booting. Under Monitor Preferences this monitor is detected as an "Ancor Communications inc 28" and the monitor preferences provides a number of resolution steps up to 1920. If I issue "xrandr --addmode HDMI-1 3840x2160" this resolution is added to the monitor preferences pick list but attempting to apply it results in "the selected configuration for displays could not ..." message To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1890418/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp