How to Fix an APC Index Mismatch BSOD

A Blue Screen of Death (BSOD) error is a catastrophic failure of your Windows operating system that forces it to restart. A BSOD is usually the result of a software bug, hardware failure, corrupt or missing software files, or malware infection—to name but a few possible causes.

BSODs can pop up at any time, and they can be difficult to troubleshoot, with complex names like “unexpected kernel mode trap” that, for most users, is impossible to decipher. An APC Index Mismatch BSOD error is just as problematic, but it usually points to a problem with your drivers or hardware. Here’s how to fix it.

What Causes an APC Index Mismatch BSOD on Windows 10?

An APC Index Mismatch (or apc_index_mismatch) BSOD error on Windows 10 is usually caused by a faulty or corrupt system driver. Audio, printer, and graphics card drivers are commonly cited as being behind this BSOD error online, but any system driver could be at fault.

This is because the error itself is linked to a failed bug check when a driver or system file reports an incorrect value during an asynchronous procedure call (APC), a type of data request made as your PC allocates system resources. Removing or replacing the problematic drivers can, for most users, fix the problem. 

If your system files are corrupted in some way, Windows itself could be behind the problem. More rarely, your hardware itself could be faulty, causing stability issues with connected hardware that causes an APC Index Mismatch BSOD message to appear when your driver attempts to interface with it.

Thankfully, most users can resolve an apc_index_mismatch BSOD by removing or replacing a corrupt driver. If this doesn’t work, more investigation might be needed. You can fix the problem by following the steps below.

Check for New System and Driver Updates

As an APC Index Mismatch BSOD is usually caused by a faulty driver, a good way to resolve the issue is to check your PC for new updates. You can check for new drivers through the Windows Update system. While you’re there, it’s a good idea to install any new system updates to fix bugs and improve your system stability.

If you can’t boot your PC currently because of this BSOD error, you may need to start Windows in Safe Mode. This should allow you to run a barebones version of Windows, running only the most basic drivers, which should stop the error from occurring temporarily and allow you to install updates. 

1. To check for new driver and system updates, right-click the Start menu and select Settings.

2. In Settings, select Update & Security > Windows Update. Windows should automatically begin a scan for new system and driver updates. If it doesn’t, select the Check for Updates button. Otherwise, select Download (or Download and Install) to begin installing new updates.

3. You may also need to select and install any optional updates listed in the Windows Update menu by selecting View options updates, as these may include optional driver updates for your PC that may resolve stability issues.

Updating your drivers should, in theory, resolve issues with your PC where an apc_index_mismatch BSOD is forcing a restart. If it doesn’t, you may need to analyze your memory dump files to determine which driver is causing the problem.

If you identify a specific device or driver causing the issue, you can then update it manually. You can also find driver updates from the manufacturer’s website, especially for devices that receive regular updates (such as graphics cards), where drivers might be newer than drivers made available through Windows Update.

Roll Back Troublesome Drivers

If you’ve identified a driver that’s causing a persistent apc_index_mismatch BSOD error by looking through your dump files, you may need to manually remove it if updating the driver doesn’t have an impact. As drivers are needed for your devices to work, rolling back to an older driver is usually the best way to do this.

While we recommend checking your dump files (.dmp) for specifics, devices including Realtek audio devices, DisplayLink monitor software, various printer drivers, and NVIDIA graphics cards have all been reported to cause this issue, and removing them may fix your PC’s BSOD problems.

1. To roll back (or remove) a driver on your PC, right-click the Start menu and select Device Manager.

2. In the Device Manager window, you’ll see hardware separated into various categories. Select the arrow icon next to each of these categories to view a full list of hardware.

3. Right-click a device with a problematic driver and select Properties.

4. In the Properties window, select the Driver tab. To remove the driver, select Uninstall Device (this will remove the driver from your system). To roll back the driver to the last installed version, select Roll Back Driver instead.

5. If you’re rolling back a driver, you’ll need to confirm why. Select a reason why you wish to roll back your driver from the options provided, then select Yes to proceed.

6. After rolling back your driver, restart your PC to make sure the change is in effect by right-clicking the Start menu and selecting Shut down or sign out > Restart.

Check for Missing or Corrupted System Files

Your device drivers are just one piece in the chain that connects running software to hardware on your PC. Windows itself is one of those pieces—if your system files are corrupted or there are missing files, Windows will stop working properly. Problems, such as an APC Index Mismatch BSOD, can then start to occur.

A good way to check for this (and to repair the problem) is to use tools to repair your Windows system files. These tools (SFC and DISM) will check the offline system image used by your PC and repair any irregularities or updates, then use that system image to repair any missing or corrupted system files that are in active use.

1. To use these tools, you’ll need to open a new PowerShell window by right-clicking the Start menu and selecting Windows PowerShell (Admin).

2. In the PowerShell window, type DISM /online /cleanup-image /restorehealth to check your offline system image for issues. Follow any additional on-screen instructions and allow this tool time to complete its scan.

3. After DISM is complete, type sfc /scannow to compare your system files against the system image created by DISM. If any files are missing or corrupted, SFC will repair them using the system image files. Follow any additional on-screen instructions and allow time for this to complete.

4. When the tools are finished, restart your PC by right-clicking the Start menu and selecting Shut down or sign out > Restart.

System Maintenance on Windows 10

If your PC suffers from an APC Index Mismatch BSOD error, don’t panic. These common troubleshooting steps should fix the problem but, in an emergency, you can always reset Windows 10 to see if that fixes the problem. If your hardware is failing, however, you may need to think about upgrading your PC for stability.

Staying on top of your system maintenance is a good way to keep BSOD errors away. You may want to automatically update high-priority drivers, such as your graphics card drivers, to ensure they’re working properly. If your PC stops working, you can always try some common PC repair tools to test and troubleshoot further.