Differences between bios and CMOS

Difference between bios and CMOS

During daily operations and maintenance of the computer, you can often hear about BIOS settings and CMOS settings. Many people often confuse bios and CMOS settings. This article mainly describes how to distinguish BIOS settings from CMOS settings in terms of basic concepts.

What is bios?

The so-called BIOS is actually the basic input-output system of a microcomputer. Its content is integrated into a ROM chip on the microcomputer motherboard, it mainly stores the most important basic input and output programs related to the microcomputer system, system information settings, power-on self-check programs, and system startup self-lifting programs.

Functions of BIOS

The bios rom chip can be seen on the motherboard, And the BIOS management function determines to a large extent whether the performance of the motherboard is superior. BiOS management functions include:

1. BIOS interrupt service program

The BIOS interrupt service program is essentially a programmable interface between software and hardware in the microcomputer system. It is mainly used to achieve the connection between the program software and the microcomputer hardware. For example, in DOS and Windows operating systems, the management of peripheral devices such as floppy disks, hard disks, optical drives, keyboards, and monitors is directly based on the BIOS system service interruption program, in addition, the operator can also directly call the BIOS interrupt service program by accessing breakpoints such as int 5 and INT 13.

2. Bios System Setup

The configuration records of microcomputer components are stored in a read/write cmos ram chip, which stores information about basic system conditions, CPU features, hard disk drives, displays, keyboards, and other components. A system setup program is installed in the bios rom chip to set parameters in cmos ram. When the program is started, press a specific key to enter the setting status, and provide a good interface for the operator to use. In fact, this process of setting CMOS parameters is also called "BIOS Settings ". If the information about the microcomputer configuration in the cmos ram chip is incorrect, the light components such as the system's overall running performance and the hard disk drive cannot be identified, in severe cases, a system hardware and software fault is triggered.

3. Post power-on self-check

After the microcomputer is powered on, the system first checks Each internal device by the post (power on self test, power on self-check) program. Generally, the complete post self-check includes testing the CPU, kb basic memory, 1 Mbit/s or more extended memory, Rom, motherboard, CMOS memory, serial port, display card, hard disk subsystem, and keyboard, once a problem is detected during self-check, the system will give a prompt or a whistle warning.

4. Start the UDF In the BIOS system.

After the system completes post self-check, the rom bios first searches for the hard drive, CD-Rom, and network server based on the boot sequence saved in the system CMOS settings to effectively start the drive, read the boot records of the operating system, hand over control of the system to the boot records, and the boot records are used to start the system smoothly.

What is CMOS?

CMOS is a read-write RAM chip on the microcomputer motherboard, it is mainly used to save the hardware configuration of the current system and set certain parameters by the operator. The cmos ram chip is powered by a back-up battery. Therefore, the CMOS information will not be lost whether it is in the shutdown status or in the case of system power loss.

The cmos ram chip is only a piece of memory and only supports data storage. Therefore, you need to set parameters in CMOS through special programs. Early CMOS settings reside on a floppy disk (such as the ibm pc/AT model), which is inconvenient to use. Currently, most manufacturers have enabled the CMOS setup program to the BIOS chip. when starting the system, you can press a specific key to enter the CMOS setup program and conveniently set the system, therefore, this CMOS setting is usually called BIOS setting.

Difference and connection between BIOS settings and CMOS settings

BIOS is an EPROM or EEPROM chip on the motherboard. It contains important information about the system and the setup program (BIOS setup program) for setting system parameters ); CMOS is a read-write RAM chip on the motherboard. It contains specific system configuration parameters. The content can be read and written through the setup program. The cmos ram chip is powered by a backup battery, and the information will not be lost even after the system powers down. Bios and CMOS are both related and different: the system setup program in BIOS is a means to complete CMOS parameter settings. cmos ram is both a place for BIOS to set system parameters and a result for BIOS to set system parameters. Therefore, the complete statement should be "setting CMOS parameters through the BIOS setup program ". Because both bios and CMOS are related to system settings, BIOS settings and CMOS settings are the same in actual use, however, bios and CMOS are two completely different concepts and must not be confused.

When should I set BIOS or CMOS?

As we all know, BIOS or CMOS setup is a very important system initialization task manually completed by the operator based on the actual situation of the microcomputer. BiOS or CMOS must be configured in the following cases:

1. purchase a new microcomputer

Even systems with the PNP function can only identify some peripheral devices of the microcomputer. The operator must set the parameters of the hard disk, the current date, the clock, and other basic information, therefore, the newly purchased microcomputer must be configured with CMOS parameters to tell the basic configuration of the entire microcomputer.

2. New Devices

Because the system may not be able to recognize new devices, it must be told through the CMOS settings. In addition, once an IRQ or DMA conflict occurs between the new device and the original device, the BIOS settings are often used for troubleshooting.

3. accidental loss of CMOS Data

When the system backup battery fails, the virus destroys the CMOS Data Program, and the CMOS parameters are accidentally cleared, the CMOS Data is often lost unexpectedly. In this case, you can only re-enter the BIOS setup program to complete the New CMOS parameter settings.

4. System Optimization

For parameters such as memory read/write wait time, hard disk data transmission mode, use of internal/external cache, energy-saving protection, power management, and startup sequence, the predefined settings in BIOs are not necessarily optimal for the system. At this time, it is often necessary to perform multiple experiments to find the optimal combination of system optimization.