How to Disable CSM (Compatibility Support Module) in Your BIOS/UEFI

If you've been trying to install Windows 11, enable Secure Boot, or switch to a GPT partition scheme, you've likely run into a setting called CSM — and been told you need to turn it off. Here's what CSM actually does, why disabling it matters, and what to expect depending on your system.

What Is CSM and Why Does It Exist?

CSM (Compatibility Support Module) is a component of UEFI firmware that emulates the older BIOS (Legacy BIOS) boot environment. It was introduced to bridge the gap when the industry transitioned from traditional BIOS to UEFI — allowing older operating systems, bootloaders, and hardware to keep functioning on newer motherboards.

When CSM is enabled, your system can boot from MBR (Master Boot Record) partitioned drives and run legacy OS installers that don't understand UEFI natively. It's essentially a backward-compatibility layer built into your firmware.

The problem is that CSM and several modern features are mutually exclusive. Secure Boot, TPM 2.0 full functionality, and fast boot all work more reliably — or only work — when CSM is disabled and the system runs in pure UEFI mode.

Why You Might Need to Disable CSM

The most common reasons people disable CSM include:

• Installing or upgrading to Windows 11, which requires Secure Boot and TPM 2.0
• Enabling Secure Boot on a system where it's currently greyed out or ineffective
• Converting a drive from MBR to GPT partition style, which pairs with UEFI boot
• Resolving GPU issues — some discrete graphics cards behave differently depending on whether CSM is active, particularly with GOP (Graphics Output Protocol) support
• Improving boot times, since pure UEFI boot is generally faster than Legacy/CSM boot

How to Disable CSM: Step-by-Step

The exact steps vary by motherboard manufacturer and firmware version, but the general process follows this pattern:

Step 1: Enter Your UEFI/BIOS Settings

Restart your computer and press the firmware access key during startup. Common keys include:

If you're on Windows 10/11, you can also navigate to Settings → System → Recovery → Advanced Startup → Restart Now, then choose Troubleshoot → Advanced Options → UEFI Firmware Settings.

Step 2: Locate the CSM Setting

Once inside your firmware, look for the CSM option. It's typically found under:

• Boot tab → CSM Configuration or Boot Mode
• Advanced tab → CSM Support
• On some systems it appears directly as "Launch CSM" or "CSM Support: Enabled/Disabled"

Firmware interfaces differ significantly. AMI, Award, and proprietary OEM interfaces (like those on Dell or HP business machines) all organize settings differently. Use your firmware's search function if one is available.

Step 3: Disable CSM and Adjust Related Settings ⚙️

Set CSM to Disabled. On some boards, disabling CSM will automatically enable or unlock Secure Boot options in the same menu — check whether Secure Boot appears and whether it's set to enabled.

You may also see sub-options like:

• Boot Device Control — set to "UEFI only"
• Storage Boot Option Control — set to "UEFI only"
• Other PCI Device ROM Priority — set to "UEFI only"

Setting these to UEFI-only ensures no component falls back to legacy behavior.

Step 4: Save and Exit

Save your changes (typically F10) and allow the system to restart. If your OS and drive were already configured for UEFI boot, the system should boot normally.

Important Variables That Affect Your Outcome 🔧

Disabling CSM isn't always straightforward, and the experience varies based on several factors:

Drive partition style: If your OS drive uses an MBR partition table, disabling CSM will likely prevent it from booting entirely. MBR drives require Legacy/CSM to boot on most systems. You'd need to convert the drive to GPT first — Windows has a built-in tool called mbr2gpt.exe for this, though it requires meeting specific conditions.

Operating system compatibility: Older operating systems (Windows 7, certain Linux distributions with older bootloaders) may not support pure UEFI boot. If you're running a legacy OS, disabling CSM without preparation will break your boot.

GPU and display output: Some older graphics cards don't have UEFI-compatible firmware (GOP). Disabling CSM on a system with one of these cards can result in no display output during POST, even if the OS boots successfully. Integrated graphics typically handle this better.

OEM vs. custom-built systems: On pre-built systems from manufacturers like Dell, HP, or Lenovo, CSM settings are sometimes locked or labeled differently. Some OEM firmware disables CSM automatically when Secure Boot is turned on, while others require manual changes.

Dual-boot configurations: If you dual-boot multiple operating systems, they each need to support UEFI boot independently before CSM can be safely disabled.

The Spectrum of Situations

A person on a modern self-built PC from the last five years with a fresh Windows 11 install on a GPT drive may find this process takes under two minutes with zero issues. Someone running a mid-2015 system that originally shipped with Windows 7, upgraded to Windows 10, and is now on an MBR drive faces a meaningfully more involved process — requiring partition conversion and bootloader repair before CSM can come out of the picture safely.

That gap between those two scenarios is wide, and your specific hardware, current OS state, partition layout, and installed components all determine which side of it you're on. 🖥️