"Uncorrectable PCI Express error detected". Common Causes of 0x12 MCE
: Issues with the processor's internal cache or instruction execution.
A transient issue where a PCIe card fails to initialize fast enough during POST, which may resolve upon a reboot. Troubleshooting and Fixes for 0x12 MCE x64 exception type 0x12 machinecheck exception link
Use the Event Viewer . Look under Windows Logs > System for "WHEA-Logger" events. This will often provide a "Section Type" (e.g., Processor or Memory) that identifies the culprit.
Key fields you may see:
Bit-flips in RAM (often detected by ECC memory but fatal on non-ECC sticks) will trigger an MCE if the CPU receives corrupted data.
The decoded output from tools like mcelog provides detailed information about error location and type, such as the one in the kernel's MCA decoder for AMD processors that specifically handles Family 12h errors, demonstrating the granularity possible when proper decoding tools are available. "Uncorrectable PCI Express error detected"
If the error identifies a specific processor or DIMM (memory slot), swap them to determine if the failure follows the part or stays on the motherboard. 4. Summary Table of MCE 0x12 Characteristics Indication Error Type Uncorrectable Machine Check Exception (MCE) Root Cause Hardware failure (CPU, RAM, PCIe, Overheat) Frequency Often persistent, requiring hardware replacement Action Immediate reboot or shutdown to prevent damage Typical Target Servers, High-performance computing, Workstations
Modify the workload profile in the BIOS. Changing the profile to or similar performance-oriented settings can sometimes prevent the processor-to-PCIe bus contention that triggers the exception. 4. Check Physical Hardware (PCIe Cards) Troubleshooting and Fixes for 0x12 MCE Use the
Disclaimer: If you are seeing this error on a production server, it is highly recommended to engage hardware support (e.g., HPE Support) for a thorough analysis of the IML logs.
: Link 0x2 mapped to the PCIe root port link attached to an NVMe storage array. The storage array’s PCIe link was negotiating at Gen4 speed, but the CPU only supported Gen3. The resulting CRC errors overflowed the PCIe AER log and triggered a fatal Machine Check Exception.