Table of contents
1. Motherboard built-in program:
BIOS (Basic Input Output System): Basic Input Output System.
UEFI (Unified Extensible Firmware Interface): Unified Extensible Firmware Interface, a new program used to replace BIOS.
1.1 Function
The built-in programs of these two motherboards are similar in function, nothing more than initializing the hardware, detecting hardware information, and then booting the system on the hard disk to run.
1.2 Comparison
Let me say a few points of comparison that are more useful to users
(1) Process:
BIOS:
UEFI：
(2) The matching partition type:
BIOS: the disk whose partition type is MBR can be used normally
UEFI: the disk whose partition type is GPT can be used normally
(3) Speed and flexibility:
BIOS: The traditional BIOS program is relatively stupid to run. It can basically only manage the hardware part, and will not interact with the system.
UEFI: Compared with the traditional BIOS, it starts faster. The traditional BIOS cannot store hardware information, and resources must be redistributed to these hardware every time it is powered on; while UEFI can store configuration information, and the hardware is not replaced every time it is powered on. Finally, you only need to allocate resources according to the configuration information. For more complex devices, UEFI can also allow the hardware itself to store its own configuration information, and provide an API to cooperate with the operating system to initialize the hardware, speeding up the operation of the system.
2. Disk partition
There are two types of disk partitions, MBR and GPT.
2.1 MBR type partition structure
MBR (Master Boot Record): Master Boot Record
● Master Boot Program (MBR): After the BIOS initialization is completed, the master boot program in sector 0 of the disk will be loaded into the memory to run. And here it 主引导程序will find the active partition, 活动分区中的引导程序(一般占一个扇区大小，即512字节)load it into the memory and run it, and then jump to the program boot that can actually boot the operating system (bootloader or GRUB2, etc. as shown in the figure below) and run the windows kernel program.
BootLoader: used to guide windows vista, 7, 8, 10
GRUB2: used to guide the operating system of linux
● Partition table (DPT): The disk in MBR format has only four partition tables, each partition table occupies 16 bytes, and corresponds to a certain primary partition in the disk. Because there are only four primary partition tables, there can only be disks with MBR type partitions. If 四个主分区you want more partitions, you can only change one of the primary partitions into an extended partition (a disk can only have one extended partition at most), and then the extended partition can be divided into Several logical partitions come out.
| Byte bit | content and meaning |
|---|---|
| 0x000 | If it is 80H, it means the partition is an active partition; if it is 00H, it means it is an inactive partition. A disk can only have one active partition, and the active partition generally stores the operating system |
| 0x001~0x003 | The address of the first sector of this partition (head number, cylinder number, sector number) |
| 0x004 | This partition type 00H: This partition is not used 05H: Extended partition 06H: FAT16 type 07H: NTFS type 0BH: FAT32 type |
| 0x005~0x007 | The address of the last sector of this partition (head number, cylinder number, sector number) |
| 0x008~0x011 | Four bytes represent the total number of sectors before this partition, so the maximum total capacity before each partition is: 2^32 * 512 = 2TB |
| 0x012~0x015 | Four bytes represent the total number of sectors of this partition, so the maximum capacity of each partition: 2^32 * 512 = 2TB |
Combining with 8 ~ 11位and 12 ~ 15位we can see that in theory, MBR partitions only support disks with a maximum capacity of 4TB. In reality, the Windows system can only allocate a maximum capacity of 2TB in the partition management. If you want to allocate 4TB, you need to use a third-party tool to partition (but this is not recommended, otherwise you will bear the consequences)
● End mark: two bytes, 0x55 and 0xAA, if not, BIOS will think that this disk cannot be booted correctly, and BIOS will continue to check the next disk in the disk list. If all disks are invalid, a boot class error will be reported.
The entire first sector above corresponds to the content in the red box in the figure below:
Note: The tool for viewing disk byte data in the figure above is called winhex
2.2 GPT type partition structure
GPT (GUID Partition Table): globally unique identifier disk partition table
● [LBA0] Protective MBR (Protective MBR): Occupies a sector size, the format is consistent with the normal MBR partition, but most of the rest are 0 except for the ending mark or 0x55 and 0xAA. On a disk with only GPT partitions, this part is only for the previous MBR disk tool to correctly identify the disk and prevent disk damage caused by misoperation.
● [LBA1] GPT Header (Primary GPT Header): Occupies a sector size, and the specific meaning is shown in the table below
| Byte bit | Bytes | content and meaning |
|---|---|---|
| 0x200~0x207 | 8 | The signature of the GPT header is translated into EFI PART through ascii code conversion |
| 0x208~0x20B | 4 | version number |
| 0x20C~0x20F | 4 | The size of meaningful data in the GPT header is generally 92 bytes, and the remaining 420 bytes are all filled with 0 |
| 0x210~0x213 | 4 | CRC checksum of the GPT header |
| 0x214~0x217 | 4 | Must be "00 00 00 00" |
| 0x218~0x21F | 8 | The starting sector number of the GPT header |
| 0x220~0x227 | 8 | The GPT header backup sector number, as shown in the figure above, is generally the last sector |
| 0x228~0x22F | 8 | The starting sector number (LBA34) that can be partitioned |
| 0x230~0x237 | 8 | The end sector number that can be partitioned (the 34th sector from the bottom) |
| 0x238~0x247 | 16 | Disk GUID (also called UUID in UNIX-like systems) |
| 0x248~0x24F | 8 | The starting sector number of the partition table (LBA2) |
| 0x250~0x253 | 4 | The total number of partition tables, because the windows system limits its maximum to 128, so theoretically windows can divide up to 128 partitions |
| 0x254~0x257 | 4 | The number of bytes occupied by each partition table, usually 128bytes |
| 0x258~0x25B | 4 | CRC checksum of all partition tables |
| 0x25C~0x3FF | 420 | Reserved bits, all 0 |
● [LBA2~LBA33] Partition table: Each partition table entry occupies 128 bytes, and because Windows can support a maximum of 128 partitions, so on a disk with Windows system, the number of bytes occupied by the entire partition table entry is = 128 bytes * 128 = 16384 bytes = 32 LBA sizes. The format of each partition table entry is as follows (take the first partition table entry as an example)
| Byte bit | Bytes | content and meaning |
|---|---|---|
| 0x400~0x40F | 16 | The partition type, GUID indicates |
| 0x410~0x41F | 16 | The unique identifier of the partition, GUID means |
| 0x420~0x427 | 8 | The starting sector of the partition, unit: LBA |
| 0x428~0x42F | 8 | The end sector of the partition, unit: LBA |
| 0x430~0x437 | 8 | The partition attribute flag |
| 0x438~0x47F | 72 | The partition name of the partition, up to 32 characters, usually these characters are encoded in UTF-16 |
See the table below for partition attributes (8 bytes=8*8bit=64bit):
| bit | content and meaning |
|---|---|
| 0 | System partition (disk partition tool must keep this partition as it is without any modification) |
| 1 | EFI hidden partition (EFI invisible partition) |
| 2 | Bootable partition flag for legacy BIOS |
| 60 | read only |
| 62 | hide |
| 63 | Do not automatically mount, that is, do not automatically assign a drive letter |
See the table below for partition types:
| operating system | GUID (little endian) | content and meaning |
|---|---|---|
| None | 00000000-0000-0000-0000-000000000000 | Unused |
| None | 024DEE41-33E7-11D3-9D69-0008C781F39F | MBR partition table |
| None | C12A7328-F81F-11D2-BA4B-00A0C93EC93B | EFI system partition |
| None | 21686148-6449-6E6F-744E-656564454649 | BIOS boot partition |
| None | D3BFE2DE-3DAF-11DF-BA40-E3A556D89593 | Intel Fast Flash (iFFS) partition (for Intel Rapid Start technology) |
| Windows | E3C9E316-0B5C-4DB8-817D-F92DF00215AE | Microsoft Reserved Partition |
| Windows | EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 | basic data partition |
| Windows | DE94BBA4-06D1-4D40-A16A-BFD50179D6AC | Windows recovery environment |
| Linux | 0FC63DAF-8483-4772-8E79-3D69D8477DE4 | Data partition. Linux used to use the same GUID as the Windows base data partition. This new GUID was invented by the GPT fdisk and GUID Parted developers based on Linux's traditional "8300" partition code. |
| Linux | A19D880F-05FC-4D3B-A006-743F0F84911E | RAID partition |
| Linux | 0657FD6D-A4AB-43C4-84E5-0933C84B4F4F | swap partition |
| Linux | E6D6D379-F507-44C2-A23C-238F2A3DF928 | Logical Volume Manager (LVM) partitions |
| Linux | 8DA63339-0007-60C0-C436-083AC8230908 | reserve |
The following are three types of partition tables, corresponding to the partition types in red, blue, and black fonts in the above partition type table
3. Summary
The UEFI+GPT solution has gradually faded out of the market due to its advantages in terms of unlimited disk capacity and operating speed. Therefore, it is recommended that if you install a system that supports UEFI+GPT, you can give priority to the UEFI+GPT solution.