What does legacy startup mean?

Legacy startup refers to the traditional BIOS startup, which is interdependent with the MBR partition mode. It can install the MBR partition system, supports the installation of all Windows systems, and has strong compatibility. As a traditional boot mode, Legacy mode supports disk partitions with MBR structure. It can boot 32-bit systems as well as 64-bit systems.

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

legacy and uefi startup are the two startup modes that need to be used when reinstalling the system.

What does legacy startup mean?

legacy startup means traditional BIOS startup, which is interdependent with MBR partition mode and can be used for MBR partition system The installation 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.

UEFI (Extensible Hardware Interface) is the new BIOS 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)

Legacy Previous, old-style, 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.

The difference between legacy and uefi startup

1. Reading speed

The traditional BIOS uses Int 13 interrupt to read the disk, which can only read 64KB each time, which is very inefficient, while UEFI can read 1MB each time and load 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 partitions 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 auto-start process. Check;

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

③. MBR starts to read the hard disk partition table DPT and finds the partition boot record in the active partition PBR, and transfer control to PBR;

④. PBR searches for the boot manager bootmgr in the active area. After finding it, PBR transfers control to bootmgr (equivalent to the ntldr file in XP);

⑤. Bootmgr looks for the BCD file in the boot folder in the active partition (startup configuration data, equivalent to the boot.ini file in xp);

⑥. After finding the BCD, Bootmgr first Read the language version information of the boot manager bootmgr menu from BCD. If there are multiple systems, 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 graphic image mode, allowing users to operate more conveniently and intuitively.

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