--- title: "SystemResponsiveness and the MMCSS Games task: values, defaults and what they do" description: "MMCSS is the Windows service that gives audio, video and game threads priority. What the tweak changes, when it helps, when it hurts and how to undo it." url: https://frozentweaks.com/tweaks/mmcss-system-responsiveness author: Frost LIVE, Founder of Frozen Tweaks published: 2026-10-08 updated: 2026-10-08 category: "CPU" source: Frozen Tweaks (https://frozentweaks.com) --- # SystemResponsiveness and the MMCSS Games task: values, defaults and what they do **Short answer:** MMCSS is the Windows service that gives audio, video and game threads priority. SystemResponsiveness is the share of processor time it keeps back for everything else, and the Games task holds the priority a game thread gets when it asks. This tweak lowers the reserve and raises the Games task values. In the registry it sets SystemResponsiveness to 10 under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile, and 5 more values. ## In the app - Switch: Tune MMCSS for Games (CPU, Pro, Advanced) - Undo: Yes. Switching it off writes the game scheduling values Windows ships with. - Game profiles that switch it on: Apex Legends, ARC Raiders, Battlefield 6 and 18 more - Catalog row: https://frozentweaks.com/tweaks#t-1011 ## What it does MMCSS is the Windows service that gives audio, video and game threads priority. SystemResponsiveness is the share of processor time it keeps back for everything else, and the Games task holds the priority a game thread gets when it asks. This tweak lowers the reserve and raises the Games task values. In the app the switch is called "Tune MMCSS for Games", described there as: Reduces SystemResponsiveness and boosts game task priority to cut scheduling jitter. ## When it helps - Games and audio that register with MMCSS, on a PC that is busy with other work at the same time. ## When it hurts - Background work (downloads, recording, a browser) gets less processor time while a game runs. - Many games never register with MMCSS, and for them the Games task values change nothing. ## What it writes Read from the app's source. "Switching it off" is what the app writes when you turn the tweak off again. Registry values: | Key | Value | With the tweak | Switching it off | | --- | --- | --- | --- | | `HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile` | `SystemResponsiveness` | `10` | 20 | | `HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games` | `Scheduling Category` | `High` | Medium | | `HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games` | `SFIO Priority` | `High` | Normal | | `HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games` | `GPU Priority` | `8` | 8 | | `HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games` | `Priority` | `6` | 2 | | `HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games` | `Affinity` | `0` | 0 | Source: Tweaks/tweaks_mmcss.hpp in the app's source, app 2.0.0, checked 2026-10-08. ## The same change by hand Run in a Command Prompt opened as administrator. Make a restore point first. ```bat reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile" /v "SystemResponsiveness" /t REG_DWORD /d 10 /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "Scheduling Category" /t REG_SZ /d "High" /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "SFIO Priority" /t REG_SZ /d "High" /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "GPU Priority" /t REG_DWORD /d 8 /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "Priority" /t REG_DWORD /d 6 /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "Affinity" /t REG_DWORD /d 0 /f ``` Put it back: ```bat reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile" /v "SystemResponsiveness" /t REG_DWORD /d 20 /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "Scheduling Category" /t REG_SZ /d "Medium" /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "SFIO Priority" /t REG_SZ /d "Normal" /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "GPU Priority" /t REG_DWORD /d 8 /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "Priority" /t REG_DWORD /d 2 /f reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games" /v "Affinity" /t REG_DWORD /d 0 /f ``` See what it is set to now: ```bat reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile" /v "SystemResponsiveness" ``` ## How to undo it Switch the tweak off in Frozen Tweaks. It writes SystemResponsiveness back to 20, Scheduling Category back to Medium, SFIO Priority back to Normal and the other values in the table. ## Verdict Low risk and reversible. Expect a difference only when the processor is contested, not an FPS number. ## Questions ### What does the "Tune MMCSS for Games" tweak change in Windows? In the registry it sets SystemResponsiveness to 10 under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile, and 5 more values. The full list is in the table on this page, read from the app's source. ### What is the standard value of SystemResponsiveness? Frozen Tweaks writes 20 when you switch the tweak off, which is the value it treats as the Windows standard. With the tweak on, SystemResponsiveness is 10. ### Is "Tune MMCSS for Games" safe to switch on? Low risk and reversible. Expect a difference only when the processor is contested, not an FPS number. The main cost: Background work (downloads, recording, a browser) gets less processor time while a game runs. ### How do I undo it? Switch the tweak off in Frozen Tweaks. Switching it off writes the game scheduling values Windows ships with. ### Is "Tune MMCSS for Games" free in Frozen Tweaks? It is part of Frozen Pro and Elite. You can also make the change by hand with the values on this page. ## Related guides - [How to Fix Stuttering and Frame Drops: Diagnose Before You Tweak](https://frozentweaks.com/guides/fix-stuttering-frame-drops) - [How to Reduce Input Lag on PC: The Whole Latency Chain](https://frozentweaks.com/guides/reduce-input-lag) ## More tweak explainers - [Timer resolution (0.5 ms)](https://frozentweaks.com/tweaks/timer-resolution-0-5-ms) - [MSI mode for HD audio](https://frozentweaks.com/tweaks/msi-mode-hd-audio) - [GPU interrupt affinity](https://frozentweaks.com/tweaks/gpu-interrupt-affinity) --- Written by Frost LIVE, founder of Frozen Tweaks. Canonical version: https://frozentweaks.com/tweaks/mmcss-system-responsiveness