A complementary metal-oxide semiconductor (CMOS) is a type of integrated circuit technology. The term is often used to refer to a battery-powered chip found in many personal computers that contains basic information, including date and time and system settings, necessary for basic input/output ( BIOS) start the computer. However, this name is somewhat misleading, as most modern computers no longer use these chips for this function, instead relying on other forms of non-volatile memory. CMOS chips are still found in many other electronic devices, including digital cameras.
CMOS microprocessor.
In a computer, the chip controls a variety of functions, including Power On Self Test (POST). When the computer’s power supply is turned on, CMOS performs a series of checks to ensure that the system is working properly. One of these checks includes the random access memory (RAM) count. This delays the boot time, so some people disable this feature in their CMOS settings and opt for fast boot instead. If you are installing a new RAM, it is better to enable the function until the RAM is verified.
A computer motherboard.
After POST completes, CMOS makes its other settings. Hard drives and formats are detected, along with Redundant Array of Independent Disk (RAID) settings, boot preferences, presence of peripherals, and overclocking settings. Many settings can be changed manually on the CMOS setup screen to improve performance; however, changes must be made by experienced users. Changing settings incorrectly can make the system unstable, cause crashes, or even prevent the computer from booting.
The configuration screen can be accessed during the POST phase of boot by pressing a key before the operating system boots. Usually this is the Del key, but it can be something else. A line of text will indicate which key will take the user to the CMOS or BIOS setup screen. Changes cannot be made in an operating system such as Microsoft Windows®, but must be made in a true DOS session. There is also an option to protect settings by requiring a password to change settings. Changes are saved by exiting by pressing the F10 key, then the computer reboots to use the new settings.
Most motherboard manuals provide a complete list of available CMOS options. They vary by motherboard design and BIOS manufacturer.
A stick of DDR-RAM, a type of memory.
