Difference between BIOS and CMOS Difference between BIOS and CMOS In the daily operation and maintenance of computer process, often heard about the BIOS settings and CMOS settings some of the claims, many people often confuse the BIOS and CMOS. This article focuses on the BIOS settings and CMOS settings in the basic conceptual distinction and connection. What is BIOS? The so-called BIOS, in fact computer&#39;s basic input output system (Basic Input-Output System), its content into the PC as a ROM chip on the motherboard, the main computer system stores information about the most important and basic input and output procedures, system information settings , boot process and system power-on self test start bootstrap procedures. BIOS function BIOS ROM chip on the motherboard can not only see but also how the BIOS management board in large part determines whether the performance is superior. BIOS management features include: 1. BIOS interrupt service routine BIOS interrupt service routine is essentially a computer system, software and a programmable interface between the hardware, software and mainly used in the process of convergence between the computer hardware. For example, DOS and Windows operating system on the floppy disk, hard drive, optical drive, keyboard, monitor and other peripheral equipment management systems are built directly BIOS interrupt service routine basis, and the operator personnel can visit INT 5, INT 13 breakpoints, etc. directly call BIOS interrupt service routine. 2. BIOS System Setup Computer components configuration record is placed in a read-write of CMOS RAM chips, mainly preserved in the basic situation of the system, CPU features, soft-hard drives, monitors, keyboards and other components of the information. In the BIOS ROM chip with &quot;system setup&quot;, mainly used to set the parameters in the CMOS RAM. This process started at boot time by pressing a specific key to enter setting mode, and provides a good interface for the operator to use. In fact, this set the CMOS process parameters, used also as &quot;BIOS settings.&quot; Once the CMOS RAM chip on the computer configuration information is incorrect, the light who will make the system reduces the overall operating performance, soft hard drive and other components can not be identified will be triggered when a severe system software and hardware failures. 3. POST Power On Self Test Computer press the power, the system first by POST (Power On Self Test, Power On Self Test) program to check each device on the inside. POST is usually complete self-test will include CPU, 640K base memory, 1M or more extended memory, ROM, motherboard, CMOS memory, serial parallel port, video card, hard disk subsystem and the soft keyboard to test, once the self in found the problem, the system will give prompt information or whistle a warning. 4. BIOS boot bootloader After completing the self-test system POST, ROM BIOS CMOS settings on the first save in accordance with the system boot sequence search software hard drive and CD-ROM, network servers effectively boot drive, read into the operating system boot record, then the system control to the boot record, boot record to complete the system by a smooth start. What is CMOS? CMOS (complementary metal oxide intended to refer to semiconductor memory din, is a large-scale manufacture of raw materials used in integrated circuit chip) is a computer motherboard&#39;s RAM chips can read and write is mainly used to save the current system&#39;s hardware configuration and the operator to set certain parameters. CMOS RAM chip from the system through a back-up battery, so either in the off state, or experience a system power-down situation, CMOS information will be lost. As the CMOS RAM chip itself is only a memory, only to save the data with the function, so the parameters of the CMOS settings in a special procedure to be adopted. Early in the CMOS setup program resides on a floppy disk (such as IBM&#39;s PC / AT type), use very convenient. Most manufacturers will now do the BIOS CMOS setup program chip, at boot time by pressing a specific key can enter the CMOS setup program and very easy to set up the system, so the CMOS settings it is often called the BIOS settings. BIOS settings and CMOS settings and their connection BIOS is the motherboard on a EPROM or EEPROM chip, which is equipped with the system&#39;s important information and set system parameters setup program (BIOS Setup program); CMOS on the motherboard is a read-write RAM chip, which is installed on the system configure specific parameters, its contents can be read and write by setting procedure. CMOS RAM chip powered by backup battery, even if the system powered off, the information will not be lost. BIOS and CMOS related, but different: BIOS in the system setup is complete CMOS parameter setting means; CMOS RAM is the system BIOS to set the storage parameters of place, but also a BIOS setting system parameters results. Therefore, the complete statement should be &quot;through the BIOS setup parameters of the CMOS settings.&quot; Since the system BIOS and CMOS settings are related to the early close correlation, so in actual use resulted in BIOS settings and CMOS settings to say, they all refer to are the same thing, but the BIOS and CMOS are two completely different concepts, Do not be confused them. When should set BIOS or CMOS? As we all know, for BIOS or CMOS settings by the operator under actual conditions of artificial computer to complete a very important system initialization. In the following cases, BIOS or CMOS must be set: 1, a new computer purchase Even with a PnP function as part of the system can only identify computer peripheral equipment, while the soft and hard parameters, the current date, basic information such as the clock must be set by the operator, the new computer purchases must be set to tell the system CMOS parameters The basic configuration of the computer. 2. New equipment Because the system does not necessarily understand the new equipment, it is necessary to tell it through the CMOS settings. In addition, once the new equipment and existing equipment took place between the IRQ, DMA conflicts, also often need to be excluded through the BIOS settings. 3. CMOS accidental loss of data Back-up battery in the system failure, virus damage the CMOS data, procedures, accident cleared the CMOS parameters such cases, accidents often result in loss of CMOS data. At this point only to re-enter the BIOS setup program to complete the new CMOS parameter settings. 4. System Optimization Wait time for read and write memory, hard disk data transfer mode, internal / external Cache use, energy conservation, power management, boot sequence and other parameters, BIOS settings on the system in terms of booking are not necessarily the best at this time After several tests are often necessary to find the best combination of system optimization.