Title:
ASRock B850 Pro-A won't fully power off after shutdown (works normally otherwise) – BIOS test rules out Windows

Hi everyone,

I'm hoping someone can help me diagnose a really strange issue.

System

• Motherboard: ASRock B850 Pro-A
• CPU: AMD Ryzen 5 7600X (using integrated graphics)
• GPU: None
• PSU: MSI MAG A650BN
• Windows: Windows 11 Pro 25H2 (Build 26200.8737)
• BIOS: 3.20 (dated 21 Feb 2025)

The PC is about 7 months old and has been working perfectly until recently.

The problem

When I click Shut Down in Windows:

• The monitor immediately loses signal.
• The keyboard LEDs (Caps Lock / Num Lock) lose power.
• Windows appears to shut down completely.
• However, the CPU cooler, case fans, and motherboard remain powered indefinitely.
• The motherboard debug LEDs (VGA and BOOT) remain lit.

The PC never reaches a fully powered-off state.

The weird part

If I enter the BIOS and press the physical power button on the case, I get exactly the same behavior:

• Display turns off.
• Fans continue spinning forever.
• CPU cooler continues running.
• Debug LEDs remain lit.

Since it also happens directly from the BIOS, I don't think Windows is causing it.

Things I've already tried

• Disabled Fast Startup.
• Ran:shutdown /s /f /t 0
• Reinstalled the latest AMD chipset driver.
• Verified Windows power settings.
• Ran:powercfg /energy powercfg /a
• Restart works perfectly every single time.
• Booting into Windows is completely normal.
• The PC is stable under load with no crashes.
• No dedicated GPU is installed.
• BIOS ACPI settings appear normal.
• USB power in S5 is disabled.
• Restore on AC Power Loss is set to Power Off.
• Deep Sleep tested.
• PCIe wake settings checked.

Additional observations

• Restart works 100% normally.
• Only shutdown is affected.
• After the failed shutdown, a short press of the power button starts the PC again.
• Holding the power button for 10+ seconds after the failed shutdown does not force it off.
• The only way to completely power it down is using the PSU switch.

Things that haven't changed

• I did not update the BIOS.
• I don't remember making any BIOS changes.
• I don't know if Windows installed a recent update automatically.

My questions

1. Has anyone seen an ASRock AM5 board fail to enter the ACPI S5 power-off state like this?
2. Could this still be a PSU issue even though restart and normal operation are perfect?
3. Is there any BIOS setting or AMD PBS/CBS option that could cause this?
4. Has anyone experienced this after a recent Windows update or BIOS firmware issue?
5. Is there anything else I should test before updating the BIOS or starting an RMA?

Any suggestions would be greatly appreciated. Thanks!