What does legacy and uefi startup mean?

Legacy boot refers to the boot method before BIOS, which is the traditional BIOS boot mode and is interdependent with the MBR partition mode. It can install the MBR partition system, supports the installation of all Win systems, and has strong compatibility; However, the MBR partition cannot support hard drives exceeding 2T and is inefficient. uefi boot refers to the boot method after BIOS. It is a new boot mode. It supports GPT partition structure and must be in GPT partition table format to boot; it can speed up the startup speed and improve the startup speed of the operating system after booting.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

Legacy and UEFI boot are both important ways to start a computer. Legacy and UEFI boot are two different boot methods of the operating system. During the computer startup process, they will determine the computer startup method and sequence. Among them, Legacy is the boot method in the traditional sense, while UEFI boot is the latest technology, which can help users start and operate the operating system more efficiently.

What does legacy boot mean

Legacy boot refers to booting from before the BIOS This method is used by the earliest PCs and IBM PCs. When the user turns on the computer, the Legacy BIOS will start executing the program pre-installed in the ROM, then load the system and boot to the operating system. Legacy boot can only support hard drives up to 2.2TB, and can only read the FAT32 file system, and cannot implement network boot.

Legacy startup means traditional BIOS startup, which is interdependent with MBR partition mode. It can install MBR partition system, supports the installation of all Windows systems, and has strong compatibility. However, the MBR partition cannot support hard drives exceeding 2T, and is inefficient and will eventually be eliminated.

Legacy Previous, old-fashioned, traditional. The hard drive boots with MBR and supports up to 4 primary partitions. This is an option in the BIOS. Previous systems used BIOS MBR; now the new standard is UEFI GPT. UEFI supports hard disk GPT partitions and can support up to 128 primary partitions.

Legacy startup is the startup method that PCs have been using for so many years (loading the startup program from the MBR). The hard disk is MBR, which is the "master boot record" of the hard disk.

What does uefi boot mean

UEFI boot refers to the boot method after BIOS, UEFI (Unified Extensible Firmware Interface) is an interface used to unify PC systems. UEFI BIOS can replace the traditional BIOS. The biggest difference between UEFI BIOS and traditional BIOS is that it has higher security, more support, and faster UEFI supports hard disk capacity up to 16TB, can recognize the exFAT file system, and can also achieve network startup.

UEFI (Extensible Hardware Interface) is the new BIOS startup boot mode, which supports GPT (GUID) partition structure and must be in GPT partition table format to start. UEFI boot can speed up the startup speed and improve the startup speed of the operating system after booting. This is why win8 and win10 systems boot quickly. However, the UEFI boot mode does not support the installation of XP/win7 systems. (If you want to install it, you must not only change the UEFI boot mode to the traditional boot mode, but also change the hard disk partition mode to MBR partition. However, some computers purchased in 2016 are not compatible with XP /win7 system, forced installation will cause USB interface failure)

The difference between legacy and uefi startup

1. Reading speed

Traditional BIOS uses Int 13 interrupt to read the disk. It can only read 64KB each time, which is very inefficient. However, UEFI can read 1MB each time and load Enter faster. In addition, Win10 has further optimized UEFI support, claiming to be able to achieve instant boot.

2. Hard disk mode

Legacy mode supports disk partitioning with MBR structure. UEFI mode only supports 64-bit systems, and the disk partition is GPT structure (GUID mode).

MBR: Master Boot Record (Master Boot Record), also called the boot sector, is the first sector that must be read when the computer is turned on to access the hard disk. The MBR partition scheme cannot support disks with a capacity exceeding 2TB.

GPT: Globally unique identification partition table (GUID Partition Table) is the partition structure of a physical hard disk. GUID Partition Table (GPT) was introduced as part of the (Extensible Firmware Interface) project. Compared with the older Master Boot Record (MBR) partitioning scheme commonly used in PCs, GPT provides a more flexible disk partitioning mechanism. Volume capacities greater than 2TB are allowed.

3. Running process

Legacy traditional BIOS startup process:

① After the computer is turned on, start the BIOS and start the BIOS self-test;

②. After passing the self-test, the bios finds the master boot record MBR on the hard disk;

③, MBR Start reading the hard disk partition table DPT, find the partition boot record PBR in the active partition, and transfer control to PBR;

④. PBR searches for the boot manager bootmgr in the active area. After finding it, PBR Control is given to bootmgr (equivalent to the ntldr file in );

⑥. After finding the BCD, Bootmgr first reads the language version information of the boot manager bootmgr menu from the BCD. If there is no multi-system, the system will be loaded directly. If there are multiple systems, the multi-operating system selection screen will be displayed.

UEFI startup process:

① After the computer is turned on, it performs power-on self-test, the UEFI firmware is loaded, and it initializes the hardware used for startup ;

②. UEFI firmware looks for the boot file (\efi\Microsoft\boot\bootmgfw.efi) in the EFI partition to start the manager;

③. The boot manager reads the hard disk EFI partition BCD file (efi\Microsoft\BCD) system menu;

④. Finally, load the boot program winload.efi (\Windows\system32\winload.efi) to load the system according to the configuration content.

Simply speaking, UEFI boot is a new type of rule that replaces Legacy boot. It is a new generation of BIOS with more powerful functions, and it is displayed in a graphical image mode, allowing users to operate more conveniently and intuitively.

Extended information:

There is another important difference between Legacy and UEFI startup mode, which is the difference in security. The security mechanism of UEFI mode is better than that of Legacy Mode is more secure, it can effectively prevent the intrusion of viruses and malware, making the system more secure and reliable. In addition, UEFI can also improve system stability, better support system upgrades, and boot the system faster.

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