UEFI secure boot is a computer startup security mechanism, which requires that the operating system and boot loader must be verified by digital signatures before they can be loaded and executed. If UEFI security boot is turned off, there may be several effects and reasons:

1. System security degradation: The purpose of UEFI security boot is to prevent malicious software and unverified operating system or boot loader from loading. Turning off the secure boot will make the system more vulnerable to malware attacks.

2. Unable to start some operating systems or drivers: Some operating systems or drivers may fail to pass the digital signature verification, and these unverified software will not be loaded and executed after the security startup is closed.

3. Unable to boot dual systems or multiple systems: If you plan to install multiple operating systems on a computer, turning off secure boot may cause some operating systems to fail to boot or have compatibility problems.

4. Hardware compatibility: Some hardware devices may rely on secure boot to ensure their normal operation, and turning off secure boot may cause these devices to fail to operate normally.

It should be noted that turning off UEFI secure boot is not always a bad choice. In some cases, it may be necessary to close it to solve some compatibility problems or implement a specific operating system or software. However, in general use, in order to ensure the security and stability of the system, it is recommended to keep UEFI powered on safely.