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<br>Nonvolatile BIOS memory refers to a small memory on Pc motherboards that's used to retailer BIOS settings. It's known as non-unstable memory or NVRAM as a result of, after the system loses energy, it does retain state by virtue of the CMOS battery. When the battery fails, BIOS settings are reset to their defaults. The battery can also be used to power an actual time clock (RTC) and the RTC, NVRAM and battery may be integrated into a single element. The identify CMOS memory comes from the technology used to make the memory, which is simpler to say than NVRAM. The CMOS RAM and the actual-time clock have been integrated as a part of the southbridge chipset they usually is probably not standalone chips on modern motherboards. In flip, the southbridge has been integrated into a single Platform Controller Hub. Alternatively BIOS settings may be saved in the pc's Super I/O chip.<br>[zhihu.com](https://www.zhihu.com/question/4159940267?write) |
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<br>The chipset built-in NVRAM capability is typically 256 bytes. For that reason, later BIOS implementations might use a small portion of BIOS flash ROM as NVRAM, to retailer BIOS setup and hardware configuration knowledge. Today's UEFI motherboards use NVRAM to retailer configuration knowledge (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 change is turned off. This battery type, in contrast to the lithium-ion battery, will not be rechargeable and trying to take action could lead to an explosion. Motherboards have circuitry preventing batteries from being charged and discharged when a motherboard is powered on. Other common battery cell varieties can last considerably longer or shorter intervals, such because the smaller CR2016 which can typically last about 40% less time than CR2032.<br> |
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<br>Larger 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. Unwanted BIOS reset may be prevented 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 maintain CMOS [Memory Wave](https://j2v.co.kr/bbs/board.php?bo_table=qa&wr_id=1003229) energized whereas the system is off. Some laptop designs have used non-button cell batteries, such as the cylindrical "1/2 AA" utilized in the ability Mac G4 as well as some older IBM Laptop compatibles, or a 3-cell nickel-cadmium (Ni-Cd) CMOS battery that looks like a "barrel" (widespread in Amiga and older IBM Computer compatibles), which serves the same objective. These motherboards often have a four pin straight header, with pin 2 lacking, for connecting to an exterior 3.6v battery, such as the Tadiran TL-5242/W, when their soldered-on batteries run out. Ni-Cd batteries have a tendency to leak devastatingly after a period of disuse, damaging components and traces on the circuit board close to the battery. Mueller, Scott (2004). Upgrading and Repairing PCS. Fisher, Tim. "What's CMOS? (CMOS & CMOS Battery Definition)". Mueller, Scott (2003). Upgrading and Repairing PCS. Mueller, Scott (2004). Upgrading and Repairing PCS. Yao, Jiewen |
