Debugged with Gemini the MSI x670E ace bios bug which was not solved since 2024 (you can see my other messages on my account)
BUG REPORT: POST Code 10 after AC Power Loss with RTX 4090 (Workaround Found)
To the MSI BIOS Engineering & Development Team,
I am writing to report a specific, reproducible early-initialization bug regarding MSI motherboards paired with NVIDIA RTX 4090 graphics cards, occurring strictly after a complete AC power loss.
Hardware Configuration:
- Motherboard: MSI MEG X670E ACE
- CPU: AMD RYZEN 7950X3D
- GPU: NVIDIA RTX 4090 (Latest VBIOS firmware applied)
- BIOS Version: Latest available version (May 2026)
The Issue (Symptoms):When the system experiences a complete AC power loss (unplugged from the wall or PSU switch turned off), the subsequent cold boot results in a hard hang at
POST Code 10 (
PEI Core is started).The system refuses to boot further. The only way to recover the system and successfully POST is by performing a hard CMOS reset.
Isolating the Variables (What was tested & ruled out):
- Memory Training / MCR: The issue is not related to memory training. "Memory Context Restore" (MCR) was completely disabled during testing.
- GPU Firmware: The RTX 4090 has the latest NVIDIA UEFI Firmware Update Tool patch applied.
- PCIe Gen Settings: Manually locking the primary PEG slot to PCIe Gen 4 (instead of Auto) did not resolve the issue.
- GOP / Visuals: Disabling the Full Screen Logo and Info Block Effects had no impact.
- Cross-Vendor Testing: The exact same RTX 4090 boots perfectly fine after an AC power loss on a motherboard from a different vendor, indicating this is specifically an MSI BIOS/logic issue.
The Solution / Workaround:The issue was completely resolved by changing
ErP Ready from
Disabled (Default) to
Enabled. With ErP Ready enabled, the system successfully passes early initialization and boots normally even after a complete AC power cut.
Technical Hypothesis for the MSI Engineering Team:This appears to be a PCIe Link Training timeout/conflict occurring during the PEI phase. When ErP Ready is
Disabled, the motherboard maintains 5VSB standby power. Upon an abrupt AC power loss, the asynchronous capacitor discharge between the MSI motherboard and the massive RTX 4090 seems to leave the PCIe bus or motherboard logic in an undefined state. When AC power is restored, the BIOS attempts early hardware polling, the GPU fails to respond within the expected MSI timeouts, and the system hangs at Code 10.
Enabling ErP Ready forces the motherboard into a true "Zero Power" state, ensuring that upon AC power restoration, the PCIe initialization starts entirely from scratch, allowing the RTX 4090 to be polled correctly.
Request: Please review the standby power handling (5VSB) and PCIe early initialization timeouts (Link Training during PEI) following abrupt power loss events for 40-series GPUs. A microcode adjustment in a future BIOS update would prevent other users from experiencing this lock-up without having to manually enable ErP Ready.
Thank you for your time and continuous work on BIOS updates.
