BIOS | FouryWang’s Blog

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What is BIOS

IOS (/ˈbaɪɒs, -oʊs/, BY-oss, -⁠ohss; an acronym for Basic Input/Output System and also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to perform hardware initialization during the booting process (power-on startup)

Originally, BIOS firmware was stored in a ROM chip on the PC motherboard.

BIOS(Basic Input Output System) 基本输入输出系统，是加载在计算机主板芯片上最基本的程序代码。它保存着计算机最重要的基本输入输出的程序、开机后自检程序和系统自启动程序。其主要功能是为计算机提供最底层的、最直接的硬件设置和控制，寻找启动设备，启动系统或其他预引导环境等。

BIOS识别硬件

BIOS（基本输入/输出系统）是计算机上的一种固件，负责在计算机启动时执行硬件初始化并将控制权交给操作系统。它同时充当硬件和操作系统之间的桥梁，使得操作系统可以与硬件进行通信。

在计算机启动时，BIOS会执行自检（称为POST，即加电自检），检测并识别连接到计算机的设备。设备识别主要依赖设备的硬件ID，这些ID通常存储在设备的ROM（只读存储器）中。硬件ID可以包括设备制造商、设备型号、序列号等信息。

对于某些设备（如硬盘、光驱、键盘、鼠标等），BIOS可以直接检测并识别它们。然而，对于其他设备（如显卡、声卡、网络适配器等），BIOS通常只识别其类别，而具体的设备名称和功能需要在操作系统层面识别和处理。

BIOS识别设备名称的过程如下：

计算机加电后，BIOS首先执行POST，检查系统硬件。

BIOS扫描系统总线（如PCI、PCIe、ISA、USB等），查询连接到总线的设备。

对于每个找到的设备，BIOS会读取其硬件ID，该ID通常存储在设备的ROM中。

BIOS根据识别到的设备信息，对硬件进行初始化并进行基本配置。

需要注意的是，BIOS仅负责基本硬件的初始化和识别。具体设备的驱动和高级功能将在操作系统加载并安装相应驱动程序后才能正常工作。在操作系统层面，设备管理器可以提供详细的设备名称和状态信息。

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ROM(固件)更新可能会导致设备名称发生变化

POST (Power-on self-test)

A power-on self-test (POST) is a process performed by firmware or software routines immediately after a computer or other digital electronic device is powered on

Option ROMs

BIOS may hand some of these duties to other programs designed to initialize very specific peripheral devices, notably for video and SCSI initialization. These other duty-specific programs are generally known collectively as option ROMs or individually as the video BIOS, SCSI BIOS, etc.

principal duties

The principal duties of the main BIOS during POST are as follows:

verify CPU registers

verify the integrity of the BIOS code itself

verify some basic components like DMA, timer, interrupt controller

initialize, size, and verify system main memory

initialize BIOS

pass control to other specialized extension BIOSes (if installed)

identify, organize, and select which devices are available for booting

The functions above are served by the POST in all BIOS versions back to the very first. In later BIOS versions, POST will also:

initialize chipset

discover, initialize, and catalog all system buses and devices

provide a user interface for system's configuration

construct whatever system environment is required by the target operating system

How BIOS Works

reset vector

In computing, the reset vector is the default location a central processing unit will go to find the first instruction it will execute after a reset. The reset vector is a pointer or address, where the CPU should always begin as soon as it is able to execute instructions. The address is in a section of non-volatile memory initialized to contain instructions to start the operation of the CPU, as the first step in the process of booting the system containing the CPU.

The BIOS has 4 main functions:

POST - Test computer hardware insuring hardware is properly functioning before starting process of loading Operating System.

Bootstrap Loader - Process of locating the operating system. If capable Operating system located BIOS will pass the control to it.

BIOS - Software / Drivers which interfaces between the operating system and your hardware. When running DOS or Windows you are using complete BIOS support.

CMOS Setup - Configuration program. Which allows you to configure hardware settings including system settings such as computer passwords, time, and date.

How BIOS Works

What new: What are the interested properties? - Feedback from BIOS and Device Driver hackers The Machine Model Every computer with a motherboard includes a special chip referred to as the BIOS or ROM BIOS ( Read Only Memory Basic Input/Output System). The BIOS includes instructions on how to load basic computer hardware.

http://flint.cs.yale.edu/feng/cos/resources/BIOS/

How BIOS Works

One of the most common uses of Flash memory is for the basic input/output system of your computer, commonly known as the BIOS. On virtually every system available, the BIOS makes sure all the other chips, hard drives, ports and CPU function together.