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This article mainly explains "what is the role of Uboot". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what is the role of Uboot".

First, why should there be Uboot?

1. The main components of the computer system:

A computer system is a system in which CPU acts as the core to run. Typical computer systems are: PC (desktop + notebook), embedded devices (mobile phones, tablets, game consoles), single-chip microcomputer (household appliances) Of course, the understanding of computer system can be likened to a manager in a management position, because when a company is started, it may not need how to manage and operate, but when the company grows slowly, if it is still the same mode of operation, it will certainly not work. Nowadays, we all pay attention to efficiency, and each employee plays a different role in the company, so he or she will assume different responsibilities. So good management is needed at this time. By associating this idea with the computer operating system, we can understand the important role of the computer system.

2. There are many components of computer systems, and different computer systems have different components. But the main core components that all computers need to run are these three things, which we are familiar with:

CPU

External storage (flash/ hard disk)

Internal memory (DDR SDRAM SDRAM SRAM)

Second, the startup process of PC:

1, the deployment of a typical PC: the BIOS program is deployed on the motherboard of the PC machine (prefabricated when the motherboard leaves the factory), the operating system is deployed on the hard disk, the memory has no effect when the power is off, and the CPU does not work when the power is off.

2, startup process: PC power on after the first execution of the BIOS program (in fact, the BIOS of PC is NorFlash), BIOS program is responsible for initializing DDR memory, responsible for initializing the hard disk, and then read the OS image from the hard disk to DDR, and then jump to DDR to execute OS until startup (BIOS is useless after OS startup).

Third, the startup process of typical embedded linux system:

1. The deployment and startup of the embedded system refer to the PC. It's just that there are some differences in equipment.

2. Deployment of typical embedded system: uboot program is deployed on Flash (Flash that can be used as boot device), OS is deployed on FLash (Flash is used instead of hard disk in embedded system), memory has no effect when power is off, CPU does not work when power is off.

3. Startup process: after the embedded system is powered on, uboot is executed first, then uboot is responsible for initializing DDR, initializing Flash, then reading OS from Flash to DDR, and then starting OS (uboot is useless after OS starts)

4. Summary: the startup process of embedded system is almost the same as that of PC, except that BIOS becomes uboot and hard disk becomes Flash.

4. Android system startup process:

1. The startup of the android system is almost the same as that of the linux system (the typical embedded system startup mentioned earlier). Almost the same meaning is exactly the same before, except after the kernel is booted and the root file system is mounted.

2. It can be considered that startup is divided into two stages: the first stage is from uboot to OS startup; the second stage is after OS startup is loaded to rootfs and executed on the command line; now we mainly study the first stage, and the difference between android startup and linux is in the second stage.

Thank you for your reading, the above is the content of "what is the role of Uboot", after the study of this article, I believe you have a deeper understanding of what the role of Uboot is, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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