How to Fix APC_INDEX_MISMATCH Error in Windows 11

The “APC_INDEX_MISMATCH” error indicates that an asynchronous procedure call (APC) was incorrectly handled by the system, leading to an inconsistency in the process queue. This error usually occurs in Windows 11 when the system encounters a problem with its driver handling processes. Poorly written drivers (Outdated drivers), corrupted system files, faulty hardware, or security software conflicts are common reasons behind this. You may encounter the APC_INDEX_MISMATCH error message accompanied by a stop code, such as 0x00000001. Well, Update or Reinstall Drivers, repair Corrupt system files with SFC and DISM restore health command help resolve the issue and restore system stability.

What is APC_INDEX_MISMATCH error?

Asynchronous Procedure Calls (APCs) are a mechanism in Windows that allows the operating system to notify a process or thread of an event without blocking the current operation. APC index is a system used by the kernel to keep track of APCs, essentially a counter for each APC that is queued or in progress.

The APC_INDEX_MISMATCH error occurs when the kernel detects an inconsistency in the APC index, meaning a driver is likely not properly managing APCs, potentially by disabling them without properly re-enabling them.

• Outdated or Incompatible Drivers – Drivers that are not compatible with Windows 11 can lead to system crashes.
• Corrupt System Files – Missing or damaged Windows system files can trigger BSOD errors.
• Conflicts with Third-Party Security Software – Some antivirus programs interfere with system processes.
• Faulty Hardware (RAM, SSD, or GPU) – Hardware issues, especially with RAM or storage, can contribute to this error.
• Windows Updates or Recent Software Changes – A recent update or software installation may conflict with system stability.
• Overclocking – Modifying CPU or GPU clock speeds beyond safe limits can lead to system instability.

Remove External Devices and Restart Your PC

A simple first step is to unplug all non-essential external devices (USB drives, external hard disks, printers, etc.) and restart your computer. Sometimes, conflicts between connected devices and drivers can trigger the APC_INDEX_MISMATCH error.

Boot Windows in Safe Mode

If your computer keeps restarting due to the error, start Windows 11 in Safe Mode to diagnose and resolve the issue.

• Turn off your computer and turn it back on.
• As soon as the Windows logo appears, press and hold the Power button to force shutdown.
• Repeat this step three times until you see the Advanced Startup menu.
• Navigate to Troubleshoot > Advanced options > Startup Settings.
• Press F4 to start Windows in Safe Mode.

Update or Reinstall Drivers

Corrupt or outdated drivers, particularly for display and audio, are common causes of this error. Updating or reinstalling them can help fix the issue.

1. Open Device Manager (Win + X > Device Manager).
2. Expand categories like Display adapters, Sound, video, and Game Controllers, and System devices.
3. Right-click the affected driver and select Update driver > Search automatically for drivers.

If updating does not help, uninstall the driver and restart your PC to allow Windows to reinstall it automatically. Also you can download the latest drivers from the manufacturer’s website and install them manually.

 

Repair system files with SFC and DISM

Again, Corrupt system files can cause blue screen of death errors, including APC_INDEX_MISMATCH. Running SFC and DISM restorehealth command scans can repair damaged files. This probably help fix the problem and restore system health back to normal.

• Open the Command Prompt as administrator (Win + S, type cmd, and select Run as administrator)
• Type command sfc /scannow and press enter key. Wait for the scan to complete and restart your PC.
• Next, run DISM restorehealth command DISM /Online /Cleanup-Image /RestoreHealth to scan and repair the Windows system image for errors.
• Let the scanning complete 100%, restart your computer and check if the problem is resolved.

Disable Realtek HD Audio or Other Conflicting Drivers

Some users have reported that Realtek HD Audio drivers can trigger the APC_INDEX_MISMATCH error. If updating the driver does not work, try disabling it.

• Open Device Manager (Win + X > Device Manager).
• Expand Sound, video, and game controllers.
• Right-click Realtek High Definition Audio and select Disable device.
• Restart your PC and check if the error persists.

Check for Faulty RAM Using Windows Memory Diagnostic

Faulty RAM can lead to BSOD errors like APC_INDEX_MISMATCH. Running a memory diagnostic test can help identify issues.

• Press Win + R, type mdsched.exe, and press Enter.
• Choose Restart now and check for problems.
• Windows will run a memory test and restart automatically.
• If errors are detected, consider replacing the faulty RAM module.

Well, if the Blue screen of death error started occurring after a Windows update, uninstalling recent updates may help. You can do it from Settings (Win + I) -> Windows Update > Update history.

In addition, if you’ve overclocked your CPU or GPU, revert the settings to default, as overclocking can cause system instability and BSOD errors. Restart your PC and enter the BIOS (F2, F10, or Del key during startup). Look for Overclocking settings and disable them.

If none of the above methods work, restoring your system to an earlier point when it was functioning correctly may resolve the error. Open Control Panel and go to Recovery > Open System Restore. Select a restore point before the APC_INDEX_MISMATCH error started occurring. Click Next, then Finish, and wait for the process to complete.