Intel-ucode package update issue

joekamprad · August 12, 2026, 12:04pm

github.com/intel/Intel-Linux-Processor-Microcode-Data-Files

Regression: Instant reboot on Core Ultra 7 155U (T14s Gen 5) with microcode 20260811

opened 08:04PM - 11 Aug 26 UTC

Updating `intel-ucode` to release `20260811` (which bumps revision from `0x28` t…o `0x2a` for file `06-aa-04`) causes an immediate hardware reboot during early boot right after selecting the kernel entry in `systemd-boot`. No `dmesg` or kernel crash logs are saved due to the reboot occurring in the early microcode loading phase. ### System Info * **Device:** Lenovo ThinkPad T14s Gen 5 * **BIOS Version:** `N46ET26W (1.16)` (Date: 04/29/2026) * **Embedded Controller (EC):** `N46HT18W` * **CPU:** Intel Core Ultra 7 155U (Family 6, Model 170 / `0xAA`, Stepping 4) * **Affected Microcode File:** `intel-ucode/06-aa-04` * **Kernel / OS:** Arch Linux, kernel `7.1.8-arch1-3` * **Bootloader:** `systemd-boot` * **Working Revision:** `0x28` (release 20260512) * **Failing Revision:** `0x2a` (release 20260811) ### Steps to Reproduce & Workaround 1. Update `intel-ucode` to release `20260811`. 2. Boot system with `initrd /intel-ucode.img` configured in `systemd-boot`. 3. Select kernel entry — system instantly triggers a hardware reboot. 4. **Workaround:** Downgrading `intel-ucode` to release `20260512` (revision `0x28`) restores normal boot behavior. ### Update / Root Cause Lenovo released BIOS version **`1.17` (`N46UR12W`)** on **11 Aug 2026**. The changelog explicitly mentions: > `- (New) Updated the CPU Microcode to version 0x2a (CPUID: 0xA06A4)` #### Findings: 1. **On BIOS 1.16 (`N46UR11W`):** Early loading microcode `0x2a` via `initrd` causes an instant hardware reset during early kernel initialization. 3. **Workaround via `dis_ucode_ldr`:** Adding `dis_ucode_ldr` to the kernel command line allows the system to boot successfully on BIOS 1.16 even with `intel-ucode.img` present in `initrd`, confirming the crash occurs strictly within the OS early microcode loader. 3. **On BIOS 1.17 (`N46UR12W`):** System boots normally without issues because microcode `0x2a` is already baked into the system firmware. Updating to vendor BIOS 1.17 works as a permanent fix, but applying early microcode updates via OS `initrd` on recent prior BIOS releases (like 1.16) should ideally not result in early-boot hardware crashes.

just in case:

https://discovery.endeavouros.com/system-rescue/arch-chroot/2022/12/

you can easily use downgrade intel-ucode from inside the chroot, and run reinstall-kernels

fro systemd-boot installs and dracut-rebuildif using grub