Are you experiencing Blue Screen of Death with the error message, APC Index mismatch? Continue reading for a solution.
The Blue Screen of Death (BSoD) is pushed off as the computer shuts down abruptly. This is because your operating system no longer knows how to handle the process causing the error and shuts down the computer in order to prevent it from damaging anything.
The Asynchronous Procedure Call (APC) is a function that is explicitly designed to run outside the main function. The APC Index Mismatch indicates an inconsistency between the number of processes entering an area of operation and the number of processes leaving it. When such a thing happens, no other process can run, resulting in a system crash.
The APC Index Mismatch usually points towards a file causing an error with a bugcheck code as well. Another common issue is because of an outdated or corrupted video or audio driver. The most common files that cause this error are:
The bugcheck code could be any of the following:
If you have encountered such an error, continue reading down the thread to rectify the problem.
Fix APC Index Mismatch BSoD In Windows 10
Uninstall Windows 10 Cumulative Update KB5000802
Microsoft had recently released a Cumulative Update KB5000802 for Windows 10 versions 2004 and 20H2. However, this update has caused an APC Index Mismatch BSoD on the majority of devices that have installed this update. Microsoft is also aware of the problem and has also mentioned it as a “Known issue” on the update’s page.
Although Microsoft has already recalled the update and is currently working on fixing the issue, if you still have it installed on your PC, follow the guide below.
If you are facing BSoD upon startup, you can resort to uninstalling the update without booting into the computer at all. Otherwise, follow the guide below to remove the update from within the OS.
Since the update is mostly installed using Windows Update, it will not be listed in the list of updates in the Control Panel, but you should be able to see it in the command line:
- Open Command Prompt (Run –> cmd)
- Run the following command:
wmic qfe list brief /format:table
- This will show all the updates installed on the computer. Make sure the relevant updates are on the list.
- To uninstall the update, run the following command
wusa /uninstall /kb:5000802
Restart your computer once the update is uninstalled.
Install other pending Windows updates
Although a Windows update is causing the APC Index Mismatch BSoD, others can fix the problem. It is reported that certain users often encounter the prompt while using a camera on Skype and other communication platforms. This is occasionally because an updated driver is incompatible with an outdated OS.
To update your Windows OS, open the Windows Update page within the Settings app and click Check for updates. The system will then automatically scan, download and install any pending updates. If the KB5000802 is already installed, we suggest that you remove it immediately.
Reinstall Realtek High Definition driver
The APC Index Mismatch BSoD can also be caused by a corrupted Realtek audio driver. Reinstalling the driver can often fix the issue. Note that this is only applicable if your computer has the associated hardware.
Go to the Realtek download page and download the driver that is right for your OS bit architecture. Once downloaded, execute the package and follow the instructions given by the installation wizard. Restart your computer for a successful installation and then check if your problem has been resolved.
Ensure all drivers are up to date
A single, small driver can turn out to be the root cause of a problem. Therefore, you must ensure that all drivers are properly installed and updated. Drivers experiencing problems are automatically highlighted with a yellow exclamation mark in the Device Manager.
To update a malfunctioning driver, open the Device Manager by typing in devmgmt.msc in Run. Now, look for the faulty driver with an exclamation mark next to its icon and right-click it. From the context menu, click Update Driver.
In the pop-up window, click Search automatically for drivers. The wizard will now search online for any updated drivers available. When it installed, restart the computer. However, if it failed to update the driver, we suggest that you go to the manufacturer’s website and manually download and install the driver package.
Uninstall Display Link driver if installed
Display Link is a third-party vendor that manufactures various IT-related devices, including monitors, as well as their drivers. Many users reportedly fixed their APC Index Mismatch issue after they removed the Display Link driver from their computers.
To remove this driver, open the Programs and Features page in the Control Panel by typing in appwiz.cpl in Run. Now double-click “DisplayLink Core” and then click Uninstall on the confirmation dialog box to remove it.
Now visit Display Link’s page and download DisplayLink Installation Cleaner. When downloaded, execute the package to clear any remaining files and folders from the driver. Once entirely removed, reboot the computer and check if the issue has been resolved.
Disable all overclocking
Hardware overclocking pushes its limits. An unstable piece of hardware can also result in APC Index Mismatch BSoD. Therefore, it is recommended that you return any hardware to its original frequencies, may it be RAM, GPU, or CPU.
If that solves the problem, we suggest that you do not overlook your hardware. If you still want to, you gradually increase its frequency without pushing the frequency too far that it starts to throw bugchecks again.
Scan for corrupted system files
As a more subtle approach, you should also check your system for any corrupted or missing system files. Windows 10 comes with a built-in tool to fix this issue. The System File Checker (SFC) automatically repairs corrupted system files that may be redundantly available on your PC, or have just gone missing.
Perform the following to run the tool:
- Launch Windows PowerShell with administrative privileges and then enter the following command:
- Now allow some time for the command to fully run and scan your PC and make any fixes if possible along the way.
- Restart the computer.
Once done, recheck if the issue persists.
Better safe than sorry! This is why a BSoD is prompted – both software and hardware are protected by shutting down the system entirely in case the system no longer understands what function(s) to perform.
If you encounter an APC Index Mismatch BSoD, be sure to check the “What failed” description on the screen. This will allow you to do a little research on the internet and determine exactly what part of the system is faulty, and then troubleshoot it accordingly.
You can read more about the PAC Index Mismatch bugcheck on Microsoft’s support page.