Nonvolatile BIOS memory: Difference between revisions

Revision as of 19:45, 2 February 2022

Revision as of 19:54, 2 February 2022

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</ref> This battery type, unlike the [[Lithium-ion battery]], is not rechargeable and trying to do so may result in an explosion. Motherboards have circuitry preventing batteries from being charged and discharged when a motherboard is powered on. Other common battery cell types can last significantly longer or shorter periods, such as the smaller [[CR2016]] which will generally last about 40% less time than CR2032. Higher temperatures and longer power-off time will shorten battery cell life. When replacing the battery cell, the system time and CMOS [[BIOS]] settings may revert to default values. Unwanted BIOS reset may be avoided by replacing the battery cell with the PSU power switch turned on and plugged into [[AC power plugs and sockets|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 computer designs have used non-button cell batteries, such as the cylindrical "[[List of battery sizes#1.2F2AA|1/2 AA]]" used in the [[Power Mac G4]] as well as some older [[IBM PC compatible]]s, or a 3-cell [[Nickel–cadmium battery|nickel–cadmium]] (Ni–Cd) CMOS battery that looks like a "[[barrel]]" (common in [[Amiga]] and older IBM PC compatibles), which serves the same purpose. These motherboards often have a four pin straight header, with pin 2 missing, for connecting to an external 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 near the battery.<ref>{{cite web | last=Williams | first=Al | date=July 8, 2018 | url=https://hackaday.com/2018/07/08/amiga-2000-emergency-repair/ | title=Amiga 2000 Emergency Repair | work=Hackaday | archiveurl=https://web.archive.org/web/20180708201017/https://hackaday.com/2018/07/08/amiga-2000-emergency-repair/ | archivedate=July 8, 2018}}</ref>

==See also==