I’m trying to troubleshoot my Lenovo Thinkpad T14s Gen 1 (AMD Ryzen 5 PRO 4650U), which has developed a strange issue. While I can enter and navigate the BIOS settings perfectly fine, the laptop reboots just seconds after trying to load any operating system. For example, when installing Windows 10 from a USB stick, the logo appears for a moment before the system restarts. Similarly, with a Debian live USB or a FreeBSD installer, the first few kernel messages are displayed on the screen, and then it immediately reboots.
What’s particularly interesting is that the Lenovo UEFI diagnostics, that I can run directly from the BIOS or from a USB stick, complete all tests for the CPU, memory, and motherboard with flying colors, reporting zero errors (about 6h of tests).
The only breakthrough I’ve had is discovering that I can successfully boot Debian by adding the noapic parameter to the kernel command line. The system is stable in this mode, but since it disables SMP it leaves me with only a single active CPU core.
Suspecting a power delivery issue from the VRM, I measured the power rails during boot attempts. The Vcore (CPU core) voltage fluctuated between 0.8V and 1.3V, which seems like a normal range. In contrast, the SOC rail consistently measured low, never exceeding 0.7-0.8V. To test if the VRM for that rail was faulty, I tried injecting 1V directly into the SOC power rail with my external bench PSU. This made no difference, and the system continued to reboot.
Any ideas?
Edit: I forgot to mention that I also tried Memtest86 with the option “all CPU cores in parallel” enabled and also these tests were completed without any errors.
