Multimedia Class Scheduler (MMCSS) Service Defaults in Windows 10

Enables relative prioritization of work based on system-wide task priorities. This is intended mainly for multimedia applications. If this service is stopped, individual tasks resort to their default priority.

Default Settings

Startup type:Automatic
Display name:Multimedia Class Scheduler
Service name:MMCSS
Service type:kernel
Error control:normal
Path:%SystemRoot%\system32\drivers\mmcss.sys
Registry key:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MMCSS

Default Behavior

Multimedia Class Scheduler is a kernel device driver. In Windows 10 it is starting automatically when the operating system starts. If Multimedia Class Scheduler fails to start, the failure details are being recorded into Event Log. Then Windows 10 will start up and notify the user that the MMCSS service has failed to start due to the error.

Restore Default Startup Configuration for Multimedia Class Scheduler

1. Run the Command Prompt as an administrator.

2. Copy the commands below, paste them into the command window and press ENTER:

sc config MMCSS start= auto
sc start MMCSS

3. Close the command window and restart the computer.

The MMCSS service is using the mmcss.sys file that is located in the %WinDir%\system32\drivers folder. If the file is changed, damaged or deleted, you can restore its original version from Windows 10 installation media.