The full name of bois system is "Basic Input Output System", which means "Basic Input Output System" in Chinese; it is actually a set of programs solidified on a ROM chip on the motherboard of the computer. It stores the most important information of the computer. The basic input and output program, the self-test program after power-on and the system self-starting program.
BIOS is the abbreviation of the English "Basic Input Output System". The literal translation of the Chinese name is "Basic Input Output System". On IBM PC-compatible systems, it is an industry-standard firmware interface. The term BIOS first appeared in the CP/M operating system in 1975. BIOS is the first software loaded when a personal computer starts up.
In fact, it is a set of programs solidified on a ROM chip on the motherboard of the computer. It stores the most important basic input and output programs of the computer, the self-test program after power-on, and the system self-startup program. Specific information about system settings can be read and written from CMOS. Its main function is to provide the lowest and most direct hardware settings and control for the computer. In addition, the BIOS also provides some system parameters to the operating system. Changes to system hardware are hidden by the BIOS, and programs use BIOS functions instead of directly controlling the hardware. Modern operating systems ignore the abstraction layer provided by the BIOS and control the hardware components directly.
Today, this system has become the target of some virus Trojans. Once this system is destroyed, the consequences will be disastrous.
Main chip
The BIOS setting program is stored in the BIOS chip. The BIOS chip is a rectangular or square chip on the motherboard. It can only be set when the computer is turned on. . (Generally, press F2 or Delete when the computer starts to enter the BIOS for settings. For some special models, press F1, Esc, F12, etc. for settings). The BIOS setup program mainly manages and sets up the computer's basic input and output system so that the system runs at its best. The BIOS setup program can also be used to troubleshoot system faults or diagnose system problems. Some people think that since BIOS is a "program", it should be software, and it feels like Word or Excel that they commonly use. But many people don't think so, because it is still somewhat different from ordinary software, and its connection with hardware is also quite close. To put it figuratively, BIOS should be a "bridge" connecting software programs and hardware devices, responsible for solving the immediate requirements of the hardware. The BIOS chip on the motherboard may be the only chip with a label on the motherboard. It is generally a 32-pin dual-in-line integrated circuit with the word "BIOS" printed on it.
ROM
In the early days of the development of microcomputers (microcomputer systems), BIOS was stored in ROM (Read Only Memory). The data inside the ROM is burned into the ROM using a special method in the factory during the ROM manufacturing process. The content can only be read and cannot be changed. Once burned in, the user can only verify whether the written data is correct. No further modifications can be made. If any errors are found in the data, it will be discarded.
EPROM
EPROM (Erasable Programmable ROM, erasable programmable ROM) chip can be erased and written repeatedly, which solves the problem that ROM chip can only be written once disadvantages. The EPROM chip has an obvious feature. There is a glass window on the front of the ceramic package. Through this window, you can see the integrated circuit inside it. Ultraviolet rays can erase the internal chip by shining it through the hole. The EPROM eraser is required to complete the chip erasing operation. A special programmer is required to write data in EPROM, and a certain programming voltage (VPP=12-24V, depending on different chip models) must be applied when writing content into the chip. The EPROM model number starts with 27. For example, 27C020 (8*256K) is an EPROM chip with a capacity of 2M Bits. After writing data to the EPROM chip, the window must be sealed with an opaque sticker or tape to prevent the data from being damaged by surrounding ultraviolet radiation.
EEPROM
Due to the inconvenience of EPROM operation, most BIOS ROM chips on motherboards after 586 use EEPROM (Electrically Erasable Programmable ROM, electrically erasable programmable ROM) ROM). Through the jumper switch and the driver disk provided with the system, the EEPROM can be rewritten to easily upgrade the BIOS.
The BIOS chip mainly stores:
●Self-diagnosis program: identify the hardware configuration by reading the contents of CMOSRAM, and perform self-test and initialization on it;
● CMOS setup program: During the boot process, use a special hotkey to start it. After setting, it is stored in CMOS RAM;
● System bootloader: After the self-test is successful, the disk Load the boot program on track 0 and sector 0 into the memory and let it run to load the DOS system;
● Drivers and interrupt services for major I/O devices: Since the BIOS directly deals with system hardware resources , so it is always aimed at a certain type of hardware system, and various hardware systems are different, so there are various types of BIOS. With the development of hardware technology, different versions of the same BIOS have appeared successively, and new This version of BIOS has more powerful functions than the old version.
NORFlash
Since the Pentium era, modern computer motherboards have used NORFlash as the BIOS memory chip. In addition to having a larger capacity than EEPROM, the main reason is that NORFlash has a writing function. The running computer can update the BIOS through software without additional hardware support (usually EEPROM erasing requires different voltages and conditions), and writing high speed.
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