Linux Kubuntu booting into dead screen on exactly every second boot

I hope you can help me. I tied a few solutions to similar problems, but none seemed to have worked for me. My set-up: - **OS**: Linux Kubuntu 19.10 - **MB**: ASUS PRIME B350-PLUS - **CPU**: AMD Ryzen 3 1300X - **GPU**: ATI Radeon HD 5450 (Dual Monitors, 2 x DVI 1920x1080) - **RAM**: 2x4GiB DDR4 - **SSD**: Boot drive is a Western Digital M.2 SSD This setup worked flawlessly until 2 weeks ago. I updated my BIOS around that time. After that the problems kept coming. The problem manifests itself as follows: **Boot number 1:** 1. BIOS information is showing 2. GRUB comes up, I select Kubuntu and hit enter 3. The screen turns black, the keyboard and mouse turn off (backlight and mouse light) 4. The 2 monitors go into power-saving mode, usb devices turn back on 5. Nothing happens, HDD_LED stays on permanently Then I press the reset button after a few minutes. **Boot number 2:** 1. BIOS information is showing 2. GRUB comes up, I select Kubuntu and hit enter 3. The screen turns black, the keyboard and mouse turn off (backlight and mouse light) 4. usb devices turn back on 5. Login screen appears Note that the screens never go into power saving mode. There is no splash screen as I turned that off with nosplash. I tried booting with nomodeset. This seems to work every time so far. But that cannot be the permanent solution to my problem, since that mode lacks the necessary support for two screens with that resolution. What I would like to know is, do you know any solution for this problem? And is there a way to read the boot messages from the previous boot? Maybe they can tell me more. ---------- **UPDATE** I finally managed to get dmesg of a failed boot (I waited on a failed boot for several minutes, to ensure that dmesg is written to /var/log/dmesg, then after the next successful boot, I found the log in /var/log/dmesg.0). This caught my eye: [ 22.864019] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 22.864030] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 27.868014] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 27.868024] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 27.868032] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing BE9E (len 821, WS 0, PS 0) @ 0xBEFB [ 32.872012] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 32.872021] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing CB6C (len 72, WS 0, PS 0) @ 0xCB9B [ 37.876016] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 37.876025] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 42.880011] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 42.880020] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 47.884011] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 47.884020] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 52.888015] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 52.888024] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 52.888095] kernel: [drm:cypress_dpm_set_power_state [radeon]] *ERROR* rv770_restrict_performance_levels_before_switch failed [ 57.892010] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 57.892019] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 57.892028] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing BE9E (len 821, WS 0, PS 0) @ 0xBEFB [ 62.896010] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 62.896019] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing CB6C (len 72, WS 0, PS 0) @ 0xCB9B [ 67.900011] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 67.900020] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 72.904010] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 72.904018] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 77.908011] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 77.908020] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 82.912010] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 82.912018] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 87.916009] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 87.916018] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 92.920008] kernel: [drm:atom_op_jump [radeon]] *ERROR* atombios stuck in loop for more than 5secs aborting [ 92.920017] kernel: [drm:atom_execute_table_locked [radeon]] *ERROR* atombios stuck executing C79C (len 62, WS 0, PS 0) @ 0xC7B8 [ 93.142085] kernel: EXT4-fs (nvme0n1p2): mounted filesystem with ordered data mode. Opts: (null) This must be the problem. But only on some boots. Now I need to find out how to fix it. ---------- **UPDATE** I remembered that I updated my BIOS a few weeks before I noticed the problems. Within these few intermittend weeks I barely used the computer, so maybe the problem was already there, I just did not see it. I was running "Version 5220 2019/09/24". So I reverted back to "Version 5216 2019/09/09". I did so by putting the .CAP file on a stick and "upgrading" the BIOS from within the BIOS menu. This took some time, but worked. After that I just booted and had no problem since. So maybe the last BIOS update was the problem. The changes for that version contain (according to ASUS): 1. Update AGESA 1.0.0.3ABBA to improve system performance. 2. Removes Gen 4 support when using Ryzen 3000 CPUs. Maybe one of these things broke Linux? Windows had no problem. BTW: If you have a similar problem with Linux sporadically not booting on this motherboard try "iommu=soft" as a parameter in the boot item for linux in GRUB.