CSM vs UEFI BIOS Mode: How do they differ?


Choosing the right BIOS mode for your computer can be confusing. Here’s a breakdown of the two modes (CSM vs UEFI) and how they differ.

What is BIOS?

BIOS is an acronym that stands for basic input/output system. It is a firmware that is used to perform hardware initialization during the boot process. BIOS also provides a runtime environment for applications and operating systems. In addition, BIOS provides a variety of services, such as power management, support for input/output devices, and support for booting from various storage devices. The BIOS is stored in read-only memory (ROM) and is typically located on the motherboard. When the computer is powered on, the BIOS performs a POST (power-on self-test) to check the status of the hardware. If everything is functioning properly, the BIOS will then load the bootloader from the storage device and hand off execution to it.

What is CSM BIOS Mode?

The CSM bios mode, or “Compatibility Support Mode”, is a boot process used by some computer systems. During this process, the system emulates an older BIOS interface in order to support legacy software and devices. This can be useful for running older operating systems or for using specialized hardware that is not compatible with newer systems. In some cases, the CSM bios mode may also offer improved compatibility with certain types of virtualization software. However, it is important to note that the CSM bios mode can also introduce potential stability issues and should only be used when absolutely necessary.

What is UEFI BIOS Mode?

UEFI, or Unified Extensible Firmware Interface, is a type of BIOS that offers increased security and performance over traditional BIOS. In order to use UEFI mode, your computer’s motherboard must support it. One of the biggest benefits of UEFI is that it supports larger hard drives than BIOS, as well as drives with a GPT partitioning scheme.UEFI also offers better security features than BIOS, making it more difficult for malware to infect your system. Finally, UEFI offers a faster boot time than BIOS, as well as support for features like Secure Boot and Fast Boot. UEFI is the future of BIOS, and is slowly becoming the new standard for PCs. If your computer supports it, you should definitely consider using it.

CSM vs UEFI BIOS: Security

When it comes to BIOS security, there are two main contenders: CSM (Compatibility Support Module) and UEFI (Unified Extensible Firmware Interface). Both have their advantages and disadvantages, but which one is more secure? Let’s take a closer look.

CSM is the older of the two technologies and is based on the traditional BIOS model. It is designed to provide backward compatibility with older operating systems and hardware. However, this also means that it is more vulnerable to attacks that exploit known vulnerabilities. In addition, CSM does not support features such as secure boot or full disk encryption, making it less secure than UEFI.

UEFI was developed as a replacement for BIOS, with security being a primary concern. It includes features such as secure boot and full disk encryption, making it much more difficult for attackers to gain access to your system. In addition, UEFI supports modern operating systems and hardware, making it less likely that you’ll run into compatibility issues. However, UEFI can be more difficult to configure than CSM, and some older systems may not support it.

So which one is more secure? That really depends on your specific needs. If you require maximum security, then UEFI is the way to go. However, if you need backward compatibility or ease of configuration, then CSM may be the better option.

CSM vs UEFI BIOS: Compatibility

CSM is compatible with a wider range of hardware and devices, while UEFI is more picky. That’s because UEFI is a newer standard that takes advantage of newer hardware features. If your motherboard doesn’t have those features, it’s not compatible with UEFI.

However, just because a motherboard is compatible with UEFI doesn’t mean it’s not compatible with CSM. In fact, most motherboards these days come with support for both BIOS standards. So if you’re not sure which one to choose, you can usually just go with the default (CSM).

Of course, there are other differences between CSM and UEFI BIOS – like boot time and security – but compatibility is the most important factor to consider when making your decision.


CSM BIOS uses 16-bit code, which can be slower than the 32-bit code used by UEFI BIOS. In addition, CSM BIOS typically requires you to press a key to access the BIOS setup utility, while UEFI BIOS can be accessed from within Windows. As a result, UEFI BIOS is generally faster and easier to use than CSM BIOS.

Additionally, UEFI also supports Fast Boot which can dramatically improve the boot times of a computer.

CSM vs UEFI BIOS: Disk Partitions

One key difference between UEFI and CSM is the way they handle disk partitions. While CSM uses the standard MBR (Master Boot Record) partitioning scheme, UEFI uses the more advanced GPT (GUID Partition Table). GPT offers many benefits over MBR, such as increased flexibility and compatibility with large disks. As a result, UEFI is now the preferred bootloader for most users.

GPT supports storage devices up to 9 ZB.

CSM vs UEFI BIOS: Drives

CSM only supports drives up to 2TB in size, while UEFI supports drives up to 16TB in size. As a result, if you have a large drive, you will need to use UEFI mode in order to access it. However, if you only have a small drive, you can use either CSM or UEFI mode. Ultimately, the choice between CSM and UEFI BIOS comes down to drive size support and compatibility. If you have a new computer with a large drive, you will need to use UEFI mode. However, if you have an older computer with a small drive, you can use either mode.

Benefits of using CSM BIOS mode

CSM BIOS mode is a legacy BIOS feature that allows Motherboards to support Operating Systems that only run on older versions of BIOS. This mode is slowly being phased out in favor of UEFI BIOS, which offers better security and compatibility with newer Operating Systems. However, there are still some benefits to using CSM BIOS mode, particularly if you are running an older Operating System or if you need to support legacy hardware.

  • One benefit is that CSM BIOS mode offers better compatibility with older Operating Systems. If you are still running Windows XP or Vista, for example, you may need to use CSM BIOS mode in order to install and run your OS.
  • Another benefit is that CSM BIOS mode offers better support for legacy hardware. If you have an old printer or other piece of hardware that is not compatible with UEFI, you may need to use CSM BIOS mode in order to get it working.

Overall, there are still some benefits to using CSM BIOS mode, even though it is gradually being phased out. However, if you are running a newer OS or if you don’t need to support legacy hardware, you may be better off using UEFI BIOS instead.

Benefits of using UEFI BIOS mode

The benefits of using UEFI BIOS mode include improved security, faster startup times, and support for large hard drives. In terms of security, UEFI provides a number of features that can help to protect your system from malware and other threats. For example, UEFI includes support for secure boot, which helps to ensure that only trusted software can run on your system. In addition, UEFI provides a number of other security features, such as Measured Boot and authenticated code modules. In terms of startup times, UEFI BIOS mode can help to speed up the boot process by allowing the operating system to load directly from the hard drive. Finally, in terms of hard drive support, UEFI BIOS mode allows you to use drives larger than 2 TB in size. Overall, the benefits of using UEFI BIOS mode make it an attractive option for both home users and businesses alike.

How do you know which BIOS mode to use?

In order to understand which BIOS mode (CSM or UEFI) is right for your computer, it is important to first understand what each mode does. CSM (Compatibility Support Module) is the traditional BIOS mode that has been used on computers for many years. In this mode, the computer boots using legacy BIOS systems. This can sometimes cause compatibility issues with newer hardware and software.

UEFI (Unified Extensible Firmware Interface) is the newer BIOS mode that is slowly becoming more popular. In this mode, the computer boots using a more modern system that is designed to work with newer hardware and software. It is important to note that not all computers support UEFI mode, so you will need to check your computer’s specifications before making any changes. In general, UEFI mode is the recommended setting for most users.

How to switch between CSM and UEFI BIOS modes?

Today’s computers are capable of running in two different BIOS modes, CSM and UEFI. CSM (Compatibility Support Module) is the traditional BIOS mode that has been used on PCs for decades. UEFI (Unified Extensible Firmware Interface) is a newer BIOS mode that is designed to replace CSM. While UEFI offers many advantages over CSM, there are still some cases where it is necessary to switch between the two modes. Here’s how to do it:

  1. Restart your computer and enter the BIOS setup utility. This can usually be done by pressing a key during the boot process, such as F1, F2, or Esc. Consult your computer’s documentation for specific instructions.
  2. Once in the BIOS setup utility, look for an option called “Boot Mode” or “Boot Type.” Use the arrow keys to select UEFI or CSM, depending on which mode you want to use.
  3. Save your changes and exit the BIOS setup utility. Your computer will now boot in the selected BIOS mode.

However, in most cases, switching from CSM to UEFI may require the assistance of a computer technician.

I am a computer engineer holding a bachelor's degree in Computer Science, complemented by a Master's in Business Administration from University of Strathclyde, Scotland. I currently work as a Senior IT Consultant in Melbourne, Australia. With over 15 years of...