BIOS+MBR and Uefi+gpt

There are two boot modes for the operating system: Legacy BIOS and UEFI

Legacy BIOS: A self-test is required at boot time and the startup process is more complicated. Because the BIOS does not recognize GPT partitions, GPT disks cannot be used to install the operating system under the traditional BIOS and can only be used for data storage

BIOS and CMOS

1.BIOS is software, program, CMOS is a chip, hardware, through the BIOS program, you can set parameters in the CMOS;

2.CMOS is a computer motherboard on a read-write RAM chip, saving important boot parameters, the CMOS button battery will be used to maintain the power, so whether in the shutdown state, or encountered the system power-down situation, CMOS information will not be lost. It is mainly used to save the hardware configuration of the current system and the operation personnel to set some parameters;

3.BIOS is (basic input/output system, the abbreviation of basic input/output systems) has played the most basic and most important role in the computer. is the most basic and most important program in the computer. This program is placed in the memory (chip) BIOS which does not require power supply, it provides the most basic and direct hardware control for the computer, and the original operation of the computer is done according to the content of the curing in the BIOS;

4.BIOS is a hardware and software program between the interface or a converter, is responsible for the real-time hardware requirements, and according to the software to the hardware operation requirements of the specific implementation, in the computer system plays a very important role.

5.BIOS and CMOS differences and linkages: the BIOS is likened to the human soul, CMOS compared to the human body, they are the relationship between the soul and the body;

UEFI: Loads the operating system directly from the pre-boot operating environment, simplifying the boot process and effectively increasing the boot speed. MBR and GPT can be identified at the same time, both MBR and GPT support the installation of the operating system in UEFI mode, although Microsoft specifies that the Windows system can only be installed using GPT hard drives in UEFI mode.

Two partition tables for hard disks: MBR and GPT. MBR: Saves partition information to 64 bytes in the first sector (MBR sector) of the disk, each partition occupies 16 bytes, which contains the active state flag, the file system ID, the start and end cylinder number, the number of magnetic number, the sector area code, the amount of implied sectors (4 bytes), the total number of partitions (4 bytes　　) and other content.　　Features: MBR partition number of primary partitions can not exceed 4, many times, 4 primary partitions do not meet the needs. MBR partitioning scheme cannot support disks that exceed 2TB capacity. Because this scheme uses 4 bytes to store the total number of sectors of the partition, the maximum can represent 2 of the number of 32 sectors, calculated as 512 bytes per sector, maximum 2TB per partition。　　After the disk capacity exceeds 2TB, the start and end location of the partition cannot be represented, and the BIOS will not recognize the partition. The abbreviation for the Gpt:guid partition table (GUID Partition table), meaning "globally unique identity disk partition table", is the standard for the structural layout of the partitioned table of an entity hard disk. In the first data block of the GTP disk there is also a tag similar to the MBR (Master boot record), called PMBR. The PMBR function is that when using a partition tool that does not support GPT, the entire hard disk will be displayed as a protected partition to prevent partition tables and hard disk data from being compromised. UEFI does not get partition information for GPT disks from PMBR, it has its own partition table, or GPT partition table. GPT's partitioning scheme is more advanced than MBR because the maximum number of partitions can be customized in the GPT partition header, which means that the size of the GPT partition table is not fixed. In Windows, Microsoft sets the maximum number of GPT disk partitions to 128. In addition, the logical block address (LBA) in the GPT partitioning scheme is represented by a 64-bit binary number, which can represent 2^64 logical block addresses.　　In addition, the GPT partitioning scheme has a backup partition table at the end of the hard disk, ensuring that the partition information is not easily lost.　　Features: Support for large hard drives above 2TB. There is almost no limit on the number of partitions per disk.　　Why do you say "almost"? Because Windows systems only allow partitioning of up to 128 partitions. There is almost no limit to the size of partitions. Because it uses a 64-bit integer to represent the sector code.　　Exaggeration to say that a 64-bit integer can represent the size of the partition is already an "astronomical", for several years you can not see such a size of hard disk, let alone partition. The partition table comes with a backup. A copy of the same partition table is saved on the first and last part of the disk, one of which is destroyed and can be recovered by another.

BIOS+MBR and Uefi+gpt