Nonvolatile BIOS Memory
Nonvolatile BIOS memory refers to a small memory on Pc motherboards that is used to store BIOS settings. It is known as non-unstable Memory Wave System or NVRAM as a result of, after the system loses energy, it does retain state by advantage of the CMOS battery. When the battery fails, BIOS settings are reset to their defaults. The battery will also be used to power a real time clock (RTC) and the RTC, NVRAM and Memory Wave battery could also be built-in into a single component. The name CMOS memory comes from the expertise used to make the memory, which is easier to say than NVRAM. The CMOS RAM and the actual-time clock have been built-in as a part of the southbridge chipset and they is probably not standalone chips on trendy motherboards. In flip, the southbridge has been built-in right into a single Platform Controller Hub. Alternatively BIOS settings may be stored in the computer's Tremendous I/O chip.
The chipset built-in NVRAM capability is often 256 bytes. For Memory Wave that reason, Memory Wave System later BIOS implementations could use a small portion of BIOS flash ROM as NVRAM, to store BIOS setup and hardware configuration information. Right this moment's UEFI motherboards use NVRAM to store configuration data (NVRAM is a portion of the UEFI flash ROM), however by many OEMs' design, the UEFI settings are nonetheless lost if the CMOS battery fails. CR2032 lithium coin cell. This cell battery has an estimated life of three years when energy provide unit (PSU) is unplugged or when the PSU power swap is turned off. This battery kind, unlike the lithium-ion battery, is not rechargeable and making an attempt to take action may lead to an explosion. Motherboards have circuitry preventing batteries from being charged and discharged when a motherboard is powered on. Other frequent battery cell sorts can last significantly longer or shorter durations, such because the smaller CR2016 which is able to generally final about 40% less time than CR2032.
Increased temperatures and longer power-off time will shorten battery cell life. When replacing the battery cell, the system time and CMOS BIOS settings might revert to default values. Undesirable BIOS reset could also be averted by changing the battery cell with the PSU power change turned on and plugged into an electric wall socket. On ATX motherboards, the PSU will supply 5V standby power to the motherboard to keep CMOS memory energized while the system is off. Some pc designs have used non-button cell batteries, such as the cylindrical "1/2 AA" used in the ability Mac G4 in addition to some older IBM Laptop compatibles, or a 3-cell nickel-cadmium (Ni-Cd) CMOS battery that appears like a "barrel" (frequent in Amiga and older IBM Laptop compatibles), which serves the same function. These motherboards often have a four pin straight header, with pin 2 missing, for connecting to an exterior 3.